Everyday for the past month when I start my car warm (opt temp) it idles horribly the whole car shakes and when I give it a bit of a rev it stalls out. The 2nd try it gets a bit better of a rev. But now its just getting horrible. Its just guzzling gas like super crazy and its doing no good (3-6 mpg). There are no codes and no air leaks from the air filter to throttle body. I cleaned the MAF and TB with little to no effect. The short term fuel trim is alright but the Long term is 19 percent. so confused right now.

 

The long term fuel trim should have corrected itself after a period of time . The STFT is a good sign that it is on target .

Something about a ECU " Hard Reset " that someone would know more about .

 

LTFT too big. Near to flagging codes.

Investigate why - may be any of many things but start as if an air leak i.e. see threads about that.

 

Check fuel pressure. Could be fuel inj, pressure reg, fuel pump. Might be a fuel injector that's stuck open.

 

Hi omgimali,

Are you certain the long term fuel trim is 19 percent and not -19 percent? Your warm-start poor running and poor fuel economy sound more like the engine is running rich. Possible causes could include one or more of the following: stuck-open coolant thermostat or engine coolant temperature sensor (ECTS) stuck at a resistance the ECM interprets as cold, or high resistance/open circuit/loose connector in the ECTS wiring resulting in the same. These problems can prompt the ECM to continue to apply cold-start fuel enrichment even after the engine reaches operating temperature. Other possible contributors include a leaking fuel injector as AZjag1999 mentioned, stuck-open carbon canister purge valve, etc.

How does the engine run at cold startups?

Cheers,

Don

 

It runs well when it is cold and during hard accelerations doesn't have that v8 feeling its very slow to get to 60 probably about 9-10 seconds. But I've done hard resets. I will post all of the Fuel Trims tomorrow when opt temp idle and 2500rpms

 

The MAFS can cause rich mixture.

 

Temperature sensor.

 

I've changed the coolant temp sensor whenever the crossover pipe was leaking and it bad idle happened before and after

 

Hard reset = needs to relearn trims.

Wait till they learn after a few drives.

 

I've done hard resets with no luck

 

So stop doing them and diagnose then fix what's wrong.

 

If you have random stalling be sure to check the two knock sensors on the top of the engine. I replaced one of mine which was covered in cracks and the car has not stalled once since! I had tried everything else; checked all the connections and the relays, everything seemed to be in order so I was very stumped, until I noticed the sensor was quite cracked from the years of heat.