Ok my car runs fine when warmed up in closed loop no misfire codes everything seems fine. But when its started cold it runs pretty rough and throws code P0300 in "history". it only does this in open loop cold. I have restarted the car after warm many times and no code but as soon as it sits for a day and you fire it never fails code P0300. also you even have to give it gas to start it cold but warm fires right up.. I think the parameters for open loop are wrong when i start it the A/f ratio is low I think thats what is causing the misfire. When it goes into closed loop the A/F ratio shoots from around 11.8/12.8 to 14.7:1 (Perfect).. just don't know what the open loop problems are. parameters ? any thoughts ? Thanks

 

When you start the engine cold, the PCM uses a richer target A/F ratio, depending on how cold the coolant temperature is. This is the equivalent of the "choke" on a carb'd setup. So it wouldn't be unusual to see the A/F ratio where you are reporting them. Just curious... how are you measuring A/F ratio? If you are reading it off a scanner, that is not "actual" A/F ratio the engine is running at... it is the "target" A/F ratio that the PCM is trying to achieve. There is no feedback as to actual A/F ratio, other than the O2 sensor mV's, and those aren't valid on cold start.

My initial reaction would have been to tell you to check the coolant temp sensor in the water pump, on the chance that the PCM did not know the coolant temp was very low, and was not using a richer mixture. But yours appears to be correctly targeting a richer A/F mixture on cold start, so it appears the coolant temp sensor is OK.

At this point, I would look at the BLM's for Cell 16 to see if you have some sort of a condition that is producing excessively high long term fuel corrections, which, when coupled with the cold start fuel enrichment are making the actual mixture way too rich.

 

Come on somebody Please...i did a search an found simular probs but no fix...Am I right about set parameters in open loop being wrong ?

 

Thanks...I was using Autotap and didn't even think that the A/F was wrong but I guess if the O2's are cold then I am reading bad #'s... I was almost positive it was to lean...well no actually the a/f would be right cause i'm reading wht the computer is using> nothing to do with 02's>>right ?

 

Let me offer you some friendly advice.... appears you were pushing the thread back to the top with your "Come on somebody...." post. Bumping a post to the top in a little more than an hour is frowned upon. You might want to read this thread, just to make sure you understand the rules:

http://web.camaross.com/forums/showt...&threadid=5485

 

I don't mean to bump this up but, thanks.. I agree with everyone that replied to that thread. I guess I never looked at it like that...Sorry to everyone

 

Ok over 24 hrs and one helpful reply. can someone else please add... I currently have autotap and I was looking at individual cylinder misfires and appears 3 & 4 are showing the activity (cold). I looked at the plugs and checked the wires looks good and doesn't explain it doing it in open loop only...Please gimme some suggestions....Thanks