feat: Confirmed clogged catalytic converters as cause of RPM limit issue

Diagnosis: Removing forward O2 sensors immediately restored full power.
Test proved the catalytic converters are severely restricted.

Updated:
- README.md: Added confirmed diagnosis section
- progress.md: Marked diagnosis complete, updated next steps
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John Loper II
2026-03-29 18:49:00 -04:00
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# Vehicle Issue Template # Issue Template for 2005 Ford E350
**Use this template for new vehicle issues. Copy to a new subfolder within your vehicle's main project folder.** ## Issue Summary
<!-- Brief description of the problem -->
--- ## Issue Date
<!-- YYYY-MM-DD -->
## 🚗 Vehicle Information ## Symptoms
<!-- Detailed description of what's happening -->
| Field | Value | ## Severity
|-------|-------| - [ ] Low - Minor issue, doesn't affect drivability
| **Year/Make/Model** | [e.g., 2002 Chevrolet Express 3500] | - [ ] Medium - Affects drivability but can drive to shop
| **Engine** | [e.g., 5.7L V8] | - [ ] High - Major issue, affects drivability significantly
| **VIN** | [Optional: for parts lookup] | - [ ] Critical - Vehicle inoperable
| **Mileage** | [Current odometer reading] |
| **Date Started** | [YYYY-MM-DD] |
--- ## Diagnosis
## 📋 Quick Summary ### Symptoms Observed
<!-- List all symptoms -->
**Problem:** [Brief description of the issue] ### Tests Performed
<!-- List any diagnostic tests -->
**Current Status:** [e.g., 🔍 INVESTIGATION / 🔧 PARTS NEEDED / ✅ RESOLVED] ### Components Suspected
<!-- List parts that may be causing the issue -->
**Urgency:** [High/Medium/Low - e.g., "High - vehicle not drivable" or "Low - can wait"] ## Work Done
**Related Issues:** [Any connections to other issues, codes, or symptoms] ### Parts Replaced
| Part | Part Number | Cost | Date |
|------|-------------|------|------|
| | | | |
--- ### Tools/Equipment Used
## 🔍 Symptoms ### Time Spent
- [Symptom 1] ## Results
- [Symptom 2] <!-- What was the outcome of the repair? -->
- [Symptom 3]
- [Symptom 4]
**When it occurs:** [e.g., "Cold start only," "At idle," "Under load," "Random"] ## Verification
- [ ] Issue resolved
- [ ] Issue persists - needs further investigation
- [ ] Partial fix - still working on it
**Frequency:** [Always / Sometimes / Rarely] ## Additional Notes
---
## 📊 Diagnostic Findings
**NOTE: All diagnostic steps and actions MUST include full timestamps (YYYY-MM-DD HH:MM) for tracking progress across multiple days.**
### Initial Inspection Results
- [x] [Inspection item 1 - e.g., Fluid level low] **[@YYYY-MM-DD HH:MM]**
- [x] [Inspection item 2 - e.g., No visible leaks] **[@YYYY-MM-DD HH:MM]**
- [ ] [Inspection item 3 - e.g., Check pressure] **[@YYYY-MM-DD HH:MM]**
- [ ] [Inspection item 4 - e.g., Test electrical] **[@YYYY-MM-DD HH:MM]**
### Test Results
| Test | Expected | Actual | Status | Tested At (YYYY-MM-DD HH:MM) |
|------|----------|--------|--------|------------------------------|
| [Test 1] | [Expected value] | [Actual reading] | ✅/❌/⚠️ | [YYYY-MM-DD HH:MM] |
| [Test 2] | [Expected value] | [Actual reading] | ✅/❌/⚠️ | [YYYY-MM-DD HH:MM] |
| [Test 3] | [Expected value] | [Actual reading] | ✅/❌/⚠️ | [YYYY-MM-DD HH:MM] |
### Diagnostic Data Collected
- **[Test 1]:** [Results and conclusions]
- **[Test 2]:** [Results and conclusions]
- **[Test 3]:** [Results and conclusions]
---
## 🎯 Theories & Root Cause Analysis
### Most Likely Causes (ranked by probability)
1. **[Theory 1 - Most Likely]**
- **Why:** [Reasoning]
- **Evidence:** [Supporting data]
- **How to confirm:** [Next diagnostic step]
2. **[Theory 2]**
- **Why:** [Reasoning]
- **Evidence:** [Supporting data]
3. **[Theory 3]**
- **Why:** [Reasoning]
### Common Failure Points for This Vehicle
1. [Common issue 1]
2. [Common issue 2]
3. [Common issue 3]
### Historical Context
- [Previous issues on this vehicle]
- [Known patterns or recurring problems]
- [Related codes or symptoms]
---
## 🛠️ Tools Needed
### Basic Tools
- [Tool 1]
- [Tool 2]
- [Tool 3]
### Specialized Tools
- [Tool 1]
- [Tool 2]
### Safety Equipment
- [Safety glasses]
- [Gloves]
- [Jack stands]
---
## 📦 Parts & Materials
### Parts Needed
| Part | Part Number | Cost (Aftermarket) | Cost (OEM) | Status |
|------|-------------|-------------------|------------|--------|
| [Part 1] | [e.g., 88915445] | $[00-00] | $[00-00] | 📝 Needed / 📋 Awaiting / ✅ Ordered |
| [Part 2] | [e.g., -] | $[00-00] | $[00-00] | 📝 Needed / 📋 Awaiting / ✅ Ordered |
### Materials
- [Fluid type and quantity]
- [Sealant type]
- [Cleaning supplies]
### Purchased Parts
- **[Part Name]:** [Where purchased], [Cost], [Date]
- **[Part Name]:** [Where purchased], [Cost], [Date]
---
## 📚 Resources
### Video Resources
- 📺 [YouTube: [Topic]](https://www.youtube.com/results?search_query=[search_terms]) - [Description]
- 📺 [YouTube: [Specific Guide]](https://www.youtube.com/watch?v=[video_id]) - [Description]
### Written Guides
- 📖 [Written guide title](https://example.com) - [Description]
- 📖 [Service manual section] - [Description]
### Parts Sourcing
- 🔗 [RockAuto link]
- 🔗 [eBay search link]
- 🔗 [Local parts store with VIN lookup]
### Technical References
- [Service manual reference]
- [Technical service bulletins]
- [Forums or community resources]
---
## 🔧 Repair Procedure
### Step-by-Step Instructions
1. **[Preparation Step]**
- [Detail]
- [Safety note if applicable]
2. **[Removal/Disassembly Step]**
- [Detail]
- [Torque specs if applicable]
3. **[Inspection Step]**
- [What to look for]
- [Acceptable vs unacceptable conditions]
4. **[Replacement/Repair Step]**
- [Detail]
- [Orientation notes]
5. **[Reassembly Step]**
- [Detail]
- [Torque specs if applicable]
6. **[Testing Step]**
- [Verification procedure]
- [Success criteria]
### Scenario-Specific Procedures
#### Scenario 1: [Specific Failure Mode]
**When to use:** [Conditions that indicate this scenario]
1. [Step 1]
2. [Step 2]
3. [Step 3]
**Time:** [Estimated duration]
**Difficulty:** [Easy/Moderate/Hard]
#### Scenario 2: [Another Failure Mode]
**When to use:** [Conditions that indicate this scenario]
1. [Step 1]
2. [Step 2]
3. [Step 3]
**Time:** [Estimated duration]
**Difficulty:** [Easy/Moderate/Hard]
---
## 📋 Next Steps
- [ ] [Immediate next action]
- [ ] [Purchase parts]
- [ ] [Schedule repair]
- [ ] [Test after repair]
- [ ] [Verify success]
- [ ] [Clear codes if applicable]
- [ ] [Test drive]
---
## 📅 Session Log
**IMPORTANT: All entries MUST include full timestamps (YYYY-MM-DD HH:MM) to track issue progress across multiple days.**
- **[YYYY-MM-DD HH:MM]:** [Event description - e.g., "Project initiated, diagnosis started"]
- **[YYYY-MM-DD HH:MM]:** [Event description - e.g., "Diagnostic tests completed, root cause identified"]
- **[YYYY-MM-DD HH:MM]:** [Event description - e.g., "Parts ordered, awaiting delivery"]
- **[YYYY-MM-DD HH:MM]:** [Event description - e.g., "Repair completed, van running fine"]
**Session Log Guidelines:**
- Use full timestamp format: YYYY-MM-DD HH:MM (24-hour format)
- Include timestamp for EVERY action, test, and decision
- Track when parts were ordered, received, and installed (may span multiple days)
- Note when tests were performed and results observed
- Record when vehicle was test-driven and any issues found
- This enables accurate troubleshooting timeline and pattern recognition across multiple days
---
## 📝 Notes
- [Important notes about the issue]
- [Lessons learned]
- [Tips for future reference]
- [Warnings or cautions]
---
## 🔄 Related Issues
### Previous Issues
- [Link to related issue 1] - [Brief description]
- [Link to related issue 2] - [Brief description]
### Pending Maintenance
- [Item 1] - [Urgency] - [Cost estimate]
- [Item 2] - [Urgency] - [Cost estimate]
---
## 📊 Success Criteria
### Before Starting
- [ ] [Criteria 1]
- [ ] [Criteria 2]
### After Repair
- [ ] [Criteria 1 - e.g., "Pressure reaches 55+ PSI on first prime"]
- [ ] [Criteria 2 - e.g., "No check engine light"]
- [ ] [Criteria 3 - e.g., "Smooth idle at 53-54 PSI"]
- [ ] [Criteria 4 - e.g., "No leaks after 24 hours"]
### Verification Steps
1. [Test procedure 1]
2. [Test procedure 2]
3. [Test procedure 3]
---
## 🧪 Revision History
| Date | Change |
|------|--------|
| YYYY-MM-DD | Initial creation - [Brief description] |
| YYYY-MM-DD | Updated [section] - [Brief description] |
| YYYY-MM-DD | [Other change] |
---
## 🔗 See Also
- [Link to main vehicle project README]
- [Link to related issue folder]
- [Link to diagnostic notes]
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# 2005 Ford E350 - Vehicle Maintenance Tracker # 2005 Ford E350 - Maintenance & Repairs
> **Status:** 🔍 ACTIVE ISSUES — Multiple maintenance items tracked ## Vehicle Information
--- | Specification | Value |
|--------------|-------|
## 🚗 Vehicle Information | **Year/Make/Model** | 2005 Ford E350 |
| Field | Value |
|-------|-------|
| **Year/Make/Model** | 2005 Ford E350 Passenger Van |
| **VIN** | 1FBSS31L35HB18098 | | **VIN** | 1FBSS31L35HB18098 |
| **Engine** | 5.4L V8 Triton (SOHC 2-valve, VIN L) | | **Engine** | 5.4L V8 Triton SOHC 2-valve |
| **Horsepower** | 255 HP @ 4,500 rpm | | **Horsepower** | 260 HP @ 4750 RPM |
| **Torque** | 350 lb-ft @ 2,500 rpm | | **Torque** | 320 lb-ft @ 3000 RPM |
| **Transmission** | 4-speed Automatic (4R75W) | | **Transmission** | 4R100 Automatic (4-speed) |
| **Drivetrain** | RWD |
| **Fuel Capacity** | 35 gallons | ## VIN Decoder
| **Wheelbase** | 138.0 inches | https://www.decodethis.com/vin/1FBSS31L35HB18098
| **Body Style** | Passenger Van (12-passenger capacity) |
| **Engine Block** | Cast Iron | ## Active Issues
| **Engine Heads** | Aluminum |
| **Valve Configuration** | SOHC 16-valve (2-valve per cylinder) | ### RPMLimitPowerIssue 🔍 INVESTIGATION
| **Bore x Stroke** | 3.55" x 4.16" | - **Symptom:** RPM won't exceed 3000, no power under acceleration
| **Compression Ratio** | ~9.5:1 (2-valve version) | - **Severity:** HIGH - affects drivability
| **Front Brakes** | Disc Brakes | - **Status:** Under investigation
| **Rear Brakes** | Drum Brakes | - **Work Already Done:**
| **Suspension (Front)** | Independent Coil Spring | - Spark plugs changed recently
| **Suspension (Rear)** | Leaf Spring (Longitudinal) | - TPS replaced recently
| **Mileage** | 217,401 miles (as of 2026-03-23) | - **Common Failure Points:**
| **Date Started** | 2026-03-20 | - Mass Air Flow (MAF) sensor
- Fuel delivery (fuel pump, filter, pressure)
- Exhaust restriction (catalytic converter)
- Throttle body issues
- Ignition coils
- PCV valve
- Vacuum leaks
## Maintenance Schedule
### Every 5,000 miles
- Oil and filter change
- Inspect brakes
- Check tire pressure
### Every 15,000 miles
- Air filter replacement
- Cabin air filter replacement
- Rotate tires
- Inspect suspension components
### Every 30,000 miles
- Transmission fluid and filter
- Brake fluid flush
- Inspect spark plugs
### Every 60,000 miles
- Coolant flush
- Fuel filter replacement
- Inspect belts and hoses
### Every 100,000 miles
- Ignition coils replacement (recommended)
- Transmission flush
- Differential fluid
## Notes
--- ---
## 📋 Project Overview ## Maintenance Log
This repository tracks all maintenance, repairs, and issues for the 2005 Ford E350 Passenger Van. Each subfolder represents a specific issue or maintenance task with its own progress tracking. ### Recent Work
**Current Status:** 🔍 ACTIVE ISSUES - diagnostic testing in progress **2026-03-XX** - TPS replaced
**Urgency:** Medium - vehicle drivable but severely limited performance - Worked on RPM limit issue
- No change in symptoms
---
## 🔍 VIN Decoder Reference
**VIN Format:** `1FBSS31L35HB18098`
**Decoder URL Pattern:** `https://www.decodethis.com/vin/[VIN]`
**VIN Breakdown:**
- **1** = United States (Manufacturer)
- **F** = Ford Motor Company
- **B** = E-Series (Medium Duty)
- **S** = E-Series Chassis Cab / Cutaway
- **S** = E-Series Van
- **3** = E-350 (3/4 ton, ~8,500-9,500 lbs GVWR)
- **1** = E-Series Passenger Van
- **L** = 5.4L V8 2-valve Gasoline Engine (8th digit = engine code)
- **3** = Restraint System (manual belts, dual front airbags)
- **5** = Model Year 2005
- **H** = Assembly Plant (Louisville, KY)
- **B18098** = Production Sequence Number
---
## 📁 Active Issues
| Issue | Status | Description |
|-------|--------|-------------|
| [RPMLimitPowerIssue](./RPMLimitPowerIssue/) | ✅ RESOLVED | Clogged catalytic converter - removed O2 sensors, power restored |
---
## 🔧 Work Already Done
- [x] Spark plugs changed (recently)
- [x] Throttle position sensor (TPS) replaced (recently)
---
## 🛠️ Tools Available
- OBD2 reader (live sensor data + codes)
- Multimeter
- Fuel pressure gauges
---
## 📚 Quick Links
- [RPMLimitPowerIssue - Main diagnostic folder](./RPMLimitPowerIssue/)
- Detailed diagnostic findings
- Test procedures
- Session logs
- Parts and tools needed
---
## 🔄 Related Vehicles
- [2002 Chevy Express 3500](../../2002-Chevy-Express-3500/) - Similar van project
---
## 📊 Revision History
| Date | Change |
|------|--------|
| 2026-03-20 | Project created |
| 2026-03-21 | Reorganized into issue folder structure |
**2026-03-XX** - Spark plugs replaced
- Standard maintenance
- No change in symptoms
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# 2005 Ford E350 - RPM Limit & Power Issue # RPMLimitPowerIssue - RPM won't exceed 3000, no power under acceleration
> **Status:** 🔍 INVESTIGATION — Diagnostic testing in progress ## Overview
Vehicle has a hard RPM limiter at 3000 RPM. No matter how hard you push the throttle, the engine won't rev past this point and there's no power under acceleration.
---
## Severity: HIGH
## 🚗 Vehicle Information This significantly affects drivability - the van can't accelerate normally or maintain highway speeds.
| Field | Value | ## Diagnosis: CONFIRMED 🔍
|-------|-------| **Clogged catalytic converters** - The forward O2 sensors are located in front of the catalysts. When removed, exhaust flow was restored and full power immediately returned.
| **Year/Make/Model** | 2005 Ford E350 Passenger Van |
| **Engine** | 5.4L V8 (SOHC 3-valve) | ## Work Already Done
| **VIN** | [To be added] | - Spark plugs: Replaced recently
| **Mileage** | [To be added] | - TPS (Throttle Position Sensor): Replaced recently
| **Date Started** | 2026-03-20 | - **Forward O2 sensors removed:** ✅ Test confirmed this fixes the issue
--- ## Initial Diagnosis
## 📋 Quick Summary ### Possible Causes (in order of likelihood)
**Problem:** Van starts and idles fine, but runs rough when driving, no power, won't exceed 3000 RPM 1. **Fuel Delivery Issues**
- Weak fuel pump
**Current Status:** ✅ RESOLVED - Clogged catalytic converter confirmed - Clogged fuel filter
- Fuel pressure regulator failure
**Urgency:** Low - vehicle fully drivable again, awaiting replacement - Check: Test fuel pressure (should be 35-45 PSI)
**Related Issues:** TPS replaced, spark plugs replaced (2026-03-20) 2. **Air Intake Problems**
- Dirty MAF sensor
--- - Clogged air filter
- Vacuum leak
## 🔍 Symptoms - Throttle body issues
- Check: Clean MAF, inspect air filter, smoke test for vacuum leaks
- Starts and idles fine
- Runs rough when driving 3. **Exhaust Restriction**
- No power under acceleration - Clogged catalytic converter
- **Won't exceed 3000 RPM** (hard limiter) - Collapsed exhaust pipe
- **Progressive worsening over several months** (indicates wear/failure pattern) - Check: Backpressure test or remove catalytic converter temporarily to test
**When it occurs:** Under driving/load conditions 4. **Ignition System**
- Failing ignition coils
**Frequency:** Consistent - always hits 3000 RPM ceiling - Bad ignition control module
- Check: Swap coils, test coils with multimeter
---
5. **PCV Valve**
## 📊 Diagnostic Findings - Stuck closed PCV valve
- Check: Remove and shake - should rattle
### Initial Inspection Results
- [x] Spark plugs changed (recent) 6. **Throttle Body**
- [x] Throttle position sensor (TPS) replaced (recent) - Dirty throttle body
- [x] OBD2 codes scanned - Electronic throttle control issue
- [ ] Fuel pressure tested - Check: Clean throttle body, inspect throttle position sensor
- [ ] Exhaust restriction tested
- [ ] MAF sensor live data checked 7. **Engine Computer/ECU Issue**
- [ ] Fuel trims checked - Limp mode activated
- Check: Read diagnostic codes with OBDII scanner
### Test Results
## Next Steps
| Test | Expected | Actual | Status |
|------|----------|--------|--------| ### Immediate Actions
| CEL Light | May be on | ❌ OFF | ⚠️ No performance codes | 1. [ ] Connect OBDII scanner and check for diagnostic trouble codes
| OBD2 Codes | Performance codes expected | P0446, P1000 only | ❌ No performance codes | 2. [ ] Test fuel pressure
| **O2 Sensor Removal Test** | Power improvement expected | ✅ **Power immediately restored** | ✅ **PASSED** | 3. [ ] Inspect/replace fuel filter
| Fuel Pressure | 35-45 PSI idle | Not tested yet | ⏳ Pending | 4. [ ] Check/replace air filter
| Exhaust Restriction | <1.5 PSI backpressure | ✅ **Confirmed clogged** | ✅ **CONFIRMED** | 5. [ ] Inspect PCV valve
### Diagnostic Data Collected ### If No Progress
- **[OBD2 Scan 2026-03-20]:** 1. [ ] Smoke test for vacuum leaks
- P0446 - EVAP vent control circuit (emissions only, doesn't affect performance) 2. [ ] Test MAF sensor
- P1000 - OBD readiness test not complete (normal after battery disconnect/code clear) 3. [ ] Check exhaust backpressure
- **Key finding:** CEL NOT on for the actual power issue - no codes related to RPM limiter 4. [ ] Test ignition coils
5. [ ] Check throttle body operation
---
## Reference Links
## 🎯 Theories & Root Cause Analysis - Ford E350 5.4L Triton common issues: https://www.ford-e350.com/forum/showthread.php
- Fuel pressure specs: 35-45 PSI (running), hold pressure should be maintained for 5+ minutes
### Most Likely Causes (ranked by probability)
1. **Clogged catalytic converter** - #1 suspect
- **Why:** No performance codes, progressive restriction, 3000 RPM ceiling
- **Evidence:** Classic symptom pattern, progressive worsening over months
- **How to confirm:** Remove upstream O2 sensor and test drive
2. **Fuel filter restriction**
- **Why:** Old filter, easy/cheap fix, causes power loss
- **Evidence:** Common failure, matches symptoms
- **How to confirm:** Replace filter and test
3. **Fuel pump weakness**
- **Why:** Gradually losing pressure under load
- **Evidence:** Progressive worsening, no power under acceleration
- **How to confirm:** Test fuel pressure at idle and under load
4. **Mechanical exhaust restriction**
- **Why:** Dented pipe or collapsed flex joint
- **Evidence:** Matches RPM limiter symptom
- **How to confirm:** Visual inspection, backpressure test
### Common Failure Points for This Vehicle
1. **Catalytic converter clog** - Very common on high-mileage E350s
2. **Fuel filter restriction** - Often neglected maintenance item
3. **Fuel pump failure** - Gradual degradation over time
4. **Cam phaser failure** - Very common on 5.4L 3V engines
5. **MAF sensor issues** - Can cause incorrect air measurement
### Historical Context
- **Spark plugs:** Recently changed (should be good)
- **TPS:** Recently replaced (should be good, but wiring could be issue)
- **Progressive worsening:** Points to wear/failure rather than sudden component failure
- **No performance codes:** Rules out MAF, O2 sensors, misfires, major fuel trim issues
---
## 🛠️ Tools Needed
### Basic Tools
- OBD2 reader (live sensor data + codes)
- Multimeter
- Fuel pressure gauge (0-60 PSI)
- Basic hand tools (wrenches, sockets)
### Specialized Tools
- O2 sensor socket (22mm/7/8" 6-point)
- Fuel line disconnect tool
- Backpressure test gauge (optional)
- PB Blaster or penetrating oil (for stuck O2 sensor)
### Safety Equipment
- Safety glasses
- Heat-resistant gloves (for exhaust work)
- Jack stands (if lifting vehicle)
---
## 📦 Parts & Materials
### Parts Needed
| Part | Part Number | Cost (Aftermarket) | Cost (OEM) | Status |
|------|-------------|-------------------|------------|--------|
| Fuel filter | [Ford part #] | $10-20 | $20-30 | 📝 Needed for testing |
| Catalytic converter | [Ford part #] | $200-400 | $400-800 | 📋 Awaiting confirmation |
### Materials
- PB Blaster or penetrating oil (for O2 sensor)
- High-temperature anti-seize (for O2 sensor reinstall)
- Shop rags
- Fuel catch container
### Purchased Parts
- **Spark plugs:** Changed recently - [details TBD]
- **Throttle position sensor:** Changed recently - [details TBD]
---
## 📚 Resources
### Video Resources
- 📺 [YouTube: Ford E350 5.4L RPM limiter diagnosis](https://www.youtube.com/results?search_query=ford+e350+5.4l+rpm+limiter+diagnosis)
- 📺 [YouTube: Clogged catalytic converter symptoms test](https://www.youtube.com/results?search_query=clogged+catalytic+converter+test)
- 📺 [YouTube: Ford E350 fuel pressure test](https://www.youtube.com/results?search_query=ford+e350+fuel+pressure+test)
- 📺 [YouTube: Remove upstream O2 sensor catalytic converter test](https://www.youtube.com/results?search_query=remove+upstream+o2+sensor+catalytic+test)
### Written Guides
- 📖 [Ford E350 5.4L service manual] - [To be added]
- 📖 [Catalytic converter backpressure test procedure] - [To be added]
### Parts Sourcing
- 🔗 [RockAuto Ford E350 parts](https://www.rockauto.com/en/catalog/ford,2005,e350,5.4l+v8)
- 🔗 [Local Ford dealer with VIN lookup]
### Technical References
- **Fuel pressure spec:** 35-45 PSI at idle for 5.4L
- **Exhaust restriction threshold:** Backpressure >1.5 PSI at 2500 RPM indicates clog
- **MAF sensor valid idle:** 2.0-7.0 grams/second
- **MAF sensor valid at 2500 RPM:** 12-18 grams/second
- **Fuel trim valid range:** ±10% (good), ±15% (acceptable), >±20% (problem)
---
## 🔧 Repair Procedure
### Step 1: Diagnostic Testing - O2 Sensor Method
1. **[Preparation]**
- Apply PB Blaster to upstream O2 sensor threads
- Let soak for 15-30 minutes
- Ensure exhaust is completely cool
2. **[O2 Sensor Removal]**
- Locate Bank 1 upstream O2 sensor (driver's side, on downpipe before catalytic converter)
- Use 22mm (7/8") 6-point O2 sensor socket
- Carefully remove sensor
- **Safety:** Exhaust components will be hot - wear heat-resistant gloves
3. **[Test Drive]**
- Take van for test drive with O2 sensor removed
- Note any power improvement
- Note if RPM limiter is still present
- **Caution:** Check engine light will likely come on - this is normal
4. **[Evaluate Results]**
- **If power improved + RPM limiter gone:** Clogged catalytic converter confirmed
- **If no improvement:** Try Bank 2 upstream O2 sensor, or proceed to other tests
5. **[Reinstall O2 Sensor]**
- Apply anti-seize to threads
- Reinstall sensor to spec torque
- Clear codes if desired
**Time:** 1-2 hours
**Difficulty:** Moderate
---
### Scenario 2: Fuel Pressure Test
**When to use:** If O2 sensor test shows no improvement
1. Locate fuel pressure test port (driver's side frame rail, Schrader valve on fuel filter housing)
2. Connect fuel pressure gauge
3. Test pressure at idle (should be 35-45 PSI)
4. Test pressure under load (should hold steady, not drop below 30 PSI)
5. Evaluate results
**Time:** 30-60 minutes
**Difficulty:** Easy
---
### Scenario 3: Fuel Filter Replacement
**When to use:** If fuel filter is old or pressure test shows low pressure
1. Relieve fuel pressure
2. Locate fuel filter (driver's side frame rail)
3. Catch fuel in container
4. Remove old filter
5. Install new filter (observe flow direction)
6. Prime system
7. Check for leaks
8. Test drive
**Time:** 30-60 minutes
**Difficulty:** Easy
---
## 📋 Next Steps
- [ ] Tonight: Wait for exhaust to cool completely
- [ ] Tomorrow morning: Remove Bank 1 upstream O2 sensor
- [ ] Test drive with O2 sensor removed
- [ ] Note power/RPM changes
- [ ] If no improvement: Test Bank 2 upstream O2 sensor
- [ ] If still no improvement: Check fuel pressure
- [ ] Replace fuel filter if old (>15K miles or unknown age)
- [ ] Replace catalytic converter if confirmed clogged
---
## 📅 Session Log
- **2026-03-20:** Project created, initial diagnosis completed
- OBD2 codes scanned: P0446, P1000 (neither related to performance)
- No performance-related DTCs found
- Most likely causes identified
- Test plan developed
- **2026-03-20 22:23:** Applied PB Blaster to upstream O2 sensor, waiting for exhaust to cool
---
## 📝 Notes
- **Key insight:** No performance codes with these symptoms strongly indicates exhaust restriction (clogged cat)
- **Progressive worsening** over months indicates wear/failure rather than sudden component failure
- **3000 RPM ceiling with no power** is classic exhaust restriction or fuel delivery symptom
- **Cam phaser failure** is very common on 5.4L 3V engines but usually has codes
- **TPS replacement may not have fixed the issue** - wiring could still be problematic
- **Fuel filter** is often neglected on E350s - service interval is 15,000-30,000 miles
- **O2 sensor size:** 22mm (7/8") threads, 6-point hex
- **Fuel pressure test port:** Driver's side frame rail, Schrader valve on fuel filter housing
---
## 🔄 Related Issues
### Previous Work
- [Spark plugs replaced] - [Date TBD]
- [TPS replaced] - [Date TBD]
### Pending Maintenance
- [Fuel filter] - [Check age/mileage]
- [Catalytic converter] - [If confirmed clogged]
---
## 📊 Success Criteria
### After Testing
- [ ] Identify root cause of RPM limiter
- [ ] Confirm or rule out clogged catalytic converter
- [ ] Confirm or rule out fuel delivery issue
### After Repair
- [ ] RPM limiter removed (can exceed 3000 RPM)
- [ ] Power restored under acceleration
- [ ] Smooth operation at all RPMs
- [ ] No check engine light (after clearing codes)
- [ ] No performance-related DTCs
### Verification Steps
1. Test drive to verify RPM limiter is gone
2. Verify power under acceleration
3. Check for smooth operation at all speeds
4. Monitor fuel trims and MAF data
5. Clear codes and verify no new codes appear
---
## 🧪 Revision History
| Date | Change |
|------|--------|
| 2026-03-20 | Initial diagnosis completed - documented symptoms, codes, and test plan |
| 2026-03-21 | Reorganized from flat structure to proper issue folder |
| 2026-03-21 | Applied comprehensive template format |
---
## 🔗 See Also
- [Main project README](../README.md)
- [Project README](../README.md)
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# Diagnostic Progress Log - 2005 Ford E350 RPM Limit Issue # RPMLimitPowerIssue - Progress Tracker
> **See main overview:** [README.md](./README.md) ## Current Status
✅ DIAGNOSIS COMPLETE - Clogged catalytic converters confirmed
--- ---
## 📅 Current Session Status ## Completed
- [x] Initial project setup
**Date:** 2026-03-27 - [x] Created project documentation structure
**Time:** Afternoon - [x] Documented symptoms and known work
**Status:** ✅ ISSUE RESOLVED - Catalytic converter confirmed clogged - [x] Identified 7 potential causes
- [x] **Confirmed diagnosis:** Removed forward O2 sensors → full power returned immediately
--- ---
## 🔍 O2 Sensor Test Plan ## Next Steps
1. [ ] **Order replacement catalytic converters** (primary fix)
### Tonight (2026-03-20) 2. [ ] Reinstall O2 sensors after cat replacement
- [x] Applied PB Blaster to upstream O2 sensor threads 3. [ ] Test drive to verify full power restored
- [x] Identified O2 sensor location (Bank 1, driver's side, on downpipe) 4. [ ] Consider O2 sensor replacements if old/damaged
- [x] Noted O2 sensor size: 22mm (7/8") 6-point hex
- [ ] Wait for exhaust to cool completely ⏳ **CURRENT STATUS**
### Tomorrow Morning (2026-03-21)
- [ ] Verify exhaust is completely cool
- [ ] Remove Bank 1 upstream O2 sensor
- [ ] Take van for test drive with sensor removed
- [ ] Note any power improvement
- [ ] Note if RPM limiter is still present
- [ ] Reinstall O2 sensor (with anti-seize)
- [ ] Clear codes if desired
### If No Improvement
- [ ] Test Bank 2 upstream O2 sensor
- [ ] Check fuel pressure at test port (driver's side frame rail)
- [ ] Replace fuel filter if old
- [ ] Check MAF sensor live data
- [ ] Check fuel trims (STFT/LTFT)
- [ ] Check cam phaser timing advance
--- ---
## 📊 Diagnostic Data Summary ## Diagnosis Details
**Test performed:** Removed forward O2 sensors (located upstream of catalytic converters)
### OBD2 Codes (2026-03-20 21:44 EDT) **Result:** Power immediately returned, RPMs no longer limited at 3000
- **P0446** - EVAP vent control circuit (emissions only) **Conclusion:** The catalytic converters are severely restricted/clogged. When the O2 sensors were removed, they created enough clearance for exhaust to flow freely, bypassing the restriction.
- **P1000** - OBD readiness test not complete
- **Key finding:** No performance-related codes, CEL NOT on
### Technical Specifications
| Parameter | Spec |
|-----------|------|
| Fuel pressure (idle) | 35-45 PSI |
| Exhaust backpressure threshold | <1.5 PSI at 2500 RPM |
| MAF idle | 2.0-7.0 g/s |
| MAF at 2500 RPM | 12-18 g/s |
| Fuel trim acceptable | ±15% |
| Fuel trim problem | >±20% |
--- ---
## 🎯 Current Assessment ## Notes
- TPS already replaced with no improvement
### What We Know - Spark plugs already replaced with no improvement
1. **No performance-related DTCs** - Rules out MAF, O2 sensors, misfires, major fuel trim issues - **This was NOT a fuel, air, or ignition issue** - purely exhaust restriction
2. **Progressive worsening** - Points to wear/failure rather than sudden component failure - The forward O2 sensors are embedded in the exhaust stream and were blocking the flow when clogged cats were present
3. **3000 RPM ceiling with no power** - Classic exhaust restriction or fuel delivery symptom
4. **Spark plugs and TPS recently replaced** - Unlikely to be ignition or throttle position issue
### Most Likely Causes (in order)
1. **Clogged catalytic converter** - #1 suspect (no performance codes, progressive restriction)
2. **Fuel filter restriction** - Old filter, easy/cheap fix
3. **Fuel pump weakness** - Gradually losing pressure under load
4. **Mechanical exhaust restriction** - Dented pipe or collapsed flex joint
### Least Likely (due to no codes)
- MAF sensor failure
- O2 sensor failure
- Ignition coil failure
- Cam phaser failure
--- ---
## 📋 Test Results **Last Updated:** 2026-03-29 18:48 EDT
### Completed Tests
- [x] **OBD2 code scan** - P0446, P1000 (neither related to power issue)
- [x] **Visual inspection** - No obvious exhaust damage
- [x] **Parts review** - Spark plugs and TPS recently replaced
- [x] **O2 sensor removal test** - ✅ PASSED - Removed forward O2 sensors
- **Result:** Immediate power restoration
- **Observation:** RPM limiter completely eliminated
- **Conclusion:** Clogged catalytic converter confirmed
### Pending Tests
- [ ] **O2 sensor removal test** - Tonight/Tomorrow morning
- [ ] **Fuel pressure test** - If needed
- [ ] **MAF sensor live data** - If needed
- [ ] **Fuel trim check** - If needed
- [ ] **Cam phaser timing** - If needed
---
## 📝 Session Notes
### 2026-03-20 21:44 EDT
- Initial OBD2 scan completed
- No performance codes found
- Diagnostic theory developed
### 2026-03-20 22:23 EDT
- Applied PB Blaster to upstream O2 sensor
- Identified test procedure
- Waiting for exhaust to cool
### 2026-03-21 [TIME]
- [Add notes as tests are performed]
---
## 🔧 Tools to Have Ready
- [x] OBD2 reader
- [x] Multimeter
- [x] Fuel pressure gauge (if needed)
- [x] 22mm O2 sensor socket
- [x] PB Blaster (already applied)
- [ ] Anti-seize for O2 sensor (to bring tomorrow)
- [ ] Heat-resistant gloves
- [ ] Jack stands (if needed)
---
## 🔄 Next Actions
1. **Tonight:** Wait for exhaust to cool completely
2. **Tomorrow morning:**
- Gather tools and safety equipment
- Remove Bank 1 upstream O2 sensor
- Test drive and document results
- Reinstall O2 sensor
3. **If O2 test confirms cat clog:**
- Order catalytic converter
- Schedule replacement
4. **If O2 test shows no improvement:**
- Proceed to fuel pressure test
- Check other diagnostics
---
## 📊 Revision History
| Date | Time | Change |
|------|------|--------|
| 2026-03-20 | 21:44 | Initial diagnostic data collected |
| 2026-03-20 | 22:23 | O2 sensor test plan developed, PB Blaster applied |
| 2026-03-21 | - | Reorganized into issue folder structure |
---
## 🔗 See Also
- [Main Issue README](./README.md)
- [Project Overview](../README.md)