I have rough idle problem after changing spark plugs, fuel filter and battery. There was no rough idle problem before this work was done. Any idea what could be wrong. Once the speed is above 20 mph it seem to run fine but at stops it vibrates and seem like it may stall!

 

Hopefully I can get this problem fixed tomorrow. I suspect the problem is the spark plugs.

Here are my thoughts:
1) Maybe the coils are loose.
2)Maybe one or more of the coils were damaged when removed.
3) Incorrect spark plug gap.
4) They may have cross threaded the spark plugs when installing them.

Any other problem that I missed? I guess the fuel pressure should be checked although I doubt this is the problem.


It might be time for a new truck. This one is seven years old. This time I may buy a Toyota Tundra.

 

Its a long shot but did you clean the throttle body? I had a sputter on my 02 after I tuned it up, throttle body was all gummed, cleaned it and the sputter was gone...

 

Have you checked to see if you have any codes? They would be helpful to figure this out.

 

The engine light comes on but does not blink. The code is P0305 which is a misfire in cylinder #5.



We changed the spark plugs and had hard time because two broke and had to use special tool to remove the sleeve that got stuck. We changed the coil for cylinder 5. All the coils were found to be in specification but we still changed the coil for cylinder 5 to definitely rule out ignition issue. We changed the intake manifold gasket because it was leaking although it was a small leak. Still it needed to be changed. We cleaned the manifold before reinstalling it. We inspected the injectors and they are good. The fuel filter was changed. The compression for cylinder 5 was similar to the others some of the time but it seemed to have hard time holding compression. The piston rings seem fine. So we think there could be problem with the valves for this cylinder. I guess it could be a broken valve seat or defective valve spring or valve guide. At first I thought it could be a bad gasoline problem. Now though I think it is a valve problem.

I think we finally may have found the problem. We must inspect the valves though to be sure.

The really really strange thing is the truck drove great after this work and then started vibrating at idle like before but after I filled the tank with fresh gas it ran great again until today. Now it is running rough again!

I thought it was fixed at first but then the rough idle started again and the engine light comes on. It shakes like someone with Parkinson disease at times! At speeds above about 20 mph there is very little vibration and is most noticeable at idle.
Are valve issues common on this truck?


This truck has been very reliable until now and wonder if the change from rural driving to city driving in the past year may have caused its decline. I make a lot more stops now than before. Probably has nothing to do with my problem though! I just wonder if I had not moved if this problem would have happened.

 

Today I found engine coolant mixed with engine oil and so I had to change the oil. This means there is a cylinder head leak and yet another issue to deal with. I am afraid to drive it and will rent a car. I think the engine is just about to die and put to rest. There are so many things wrong! The compression in cylinder 5 does not hold compression caused possibly by a leaking valve. The gaskets are leaking allowing oil and engine coolant to mix. Now I have to make a decision whether to buy a new truck, rebuild the engine or buy a new engine. This engine served its useful life and now almost dead at 97,630 miles! The truck is still drive able although it has very rough idle and hesitates during acceleration. There is noticeable loss of power.

 

Maybe the manifold didn't seat properly on the gaskets