My truck misfires and will runs rough and only wants to go up to 40mph/usually am/intermittant
past had a failure code P0304 , cyclandor #4 misfire
we have replaced spark plugs, coil and fuel injector
Any other ideas as to what the problem is?
Wow, have you considered it to be more than just a misfire on cylinder 4? It could be a fuel delivery problem to the whole engine. Also, are you SURE that you are working on cylinder #4? Check and double check again. What engine does it have? I'll get you the cylinder numbering. Also, can you feel a noticeable misfire while the engine is just idling in park?
Do a compression test on all cyls this will locate the problem child, a valve w carbon stuck on the valve face will set the light,if you also have back fire it indicates a valve is open upon firing, possible burn valve may be the culprit, this would create a constant runnabilty issue. (Misfire) good compression numbers gas engines 120 - 180 psi diesel 250 - 300 anything below this range will not fire or balance the engine.
Hope that helps
Also low fuel pressure can give similar symptoms
joef-The engine is 5.7 liter HEMI. Yes, it misfires while in park. tommcmanis-I have not tried the compression test yet. Thanks
How many miles are on it? What maintenance has been done? What happened when this issue started?
87,000 miles. Maintenance-allways oil changes. Truck shaked and did not run faster than 40mph. Now it runs rough/misfires and tends to stop after the engine light goes on. The worst is in the morning. Sometimes during the day.
TPS throttle position sensor
I have a 2003 Dodge 1500. Same code replaced all the plugs and coils. After doing that and a lot of online research I removed my valve cover and found my rocker arm was thrown. It is a common occurrence in the 4,7 v8. Once you replace what the Dodge manual calls a lash adjuster and putt the rocker arm back in your error code should go away. The rocker arm thing is a common thing with the this engine and usually occurs on cold start up. Try running some fuel cleaner and or engine cleaner to clean build up. Good luck
The engine light flashing on and off is what my truck did and it will drive rough and will not drive over 40. If you can help it do not drive it due to damage it can cause to your catalytic converter.
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