John Loper II
15c1d05844
Added comprehensive step-by-step instructions for removing both catalytic converters: - Tool list with specific sizes - Safety precautions - Detailed removal steps - Reinstallation guidance - Estimated time (1-4 hours depending on experience)
RPMLimitPowerIssue - RPM won't exceed 3000, no power under acceleration
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
This significantly affects drivability - the van can't accelerate normally or maintain highway speeds.
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.
Work Already Done
- Spark plugs: Replaced recently
- TPS (Throttle Position Sensor): Replaced recently
- Forward O2 sensors removed: ✅ Test confirmed this fixes the issue
Initial Diagnosis
Possible Causes (in order of likelihood)
-
Fuel Delivery Issues
- Weak fuel pump
- Clogged fuel filter
- Fuel pressure regulator failure
- Check: Test fuel pressure (should be 35-45 PSI)
-
Air Intake Problems
- Dirty MAF sensor
- Clogged air filter
- Vacuum leak
- Throttle body issues
- Check: Clean MAF, inspect air filter, smoke test for vacuum leaks
-
Exhaust Restriction
- Clogged catalytic converter
- Collapsed exhaust pipe
- Check: Backpressure test or remove catalytic converter temporarily to test
-
Ignition System
- Failing ignition coils
- Bad ignition control module
- Check: Swap coils, test coils with multimeter
-
PCV Valve
- Stuck closed PCV valve
- Check: Remove and shake - should rattle
-
Throttle Body
- Dirty throttle body
- Electronic throttle control issue
- Check: Clean throttle body, inspect throttle position sensor
-
Engine Computer/ECU Issue
- Limp mode activated
- Check: Read diagnostic codes with OBDII scanner
Next Steps
Immediate Actions
- Connect OBDII scanner and check for diagnostic trouble codes
- Test fuel pressure
- Inspect/replace fuel filter
- Check/replace air filter
- Inspect PCV valve
If No Progress
- Smoke test for vacuum leaks
- Test MAF sensor
- Check exhaust backpressure
- Test ignition coils
- Check throttle body operation
Reference Links
- 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