Rough Idle Misfire Cold start no codes.

[TonyV2000]

My 2000 AWD 5.0 with 120K starts fine but when I start driving it sounds like it's running on only 4 cylinders. There is no power and it backfires as I try to give it more gas. Within 5 minutes or so things smooth out to almost 100% it is still a little rough when I stop at a light for instance.

There is no check engine light and no codes when I scan. Several months ago I had a P1151, but I reset it and it never returned.

I changed the plugs several months ago and recently cleaned the ICV (it was pretty clean) and the MAF sensor, no help.

I'm stuck! Any ideas would be greatly appreciated.

 

[my98nnj]

Check the engine coolant temp sensor, make sure it's within spec when it's cold.

 

[TonyV2000]

Check the engine coolant temp sensor, make sure it's within spec when it's cold.

Hi my98nnj and thanks for the reply. I haven’t checked the resistance across the ECT sensor yet but I put the scan tool on her today and noticed that before starting the engine the water temperature was reading almost 30 degrees higher then both the Intake Air Temperature and the ambient air temperature which was about 75. I guess I will need to take a closer look…. So where is it?

 

[deweyville65]

Also, are you loosing any coolant without seeing any signs of leaking?

 

[TonyV2000]

Also, are you loosing any coolant without seeing any signs of leaking?

I don't think so. No visible drips, no white smoke and no water in the oil. Why, how would a coolant leak effect this problem?

 

[deweyville65]

Because you -could- be getting coolant into one or more cylinders from a leaking head gasket, or a cracked head, causing a miss upon cold start up. So, check the coolant reservoir level. If the coolant is disappearing without seeing any leaks, it is probably burning it. You more than likely wont see any white smoke(steam), because the amount at any one time is slight.