I have used this forum before and everyone that replied was very courteous and extremely helpful in fixing the problem. I have a 98 CVPI with an issue of missing while the engine is running. My post is going to be a little lengthy as I have already tried several common solutions, but please bear with me. As stated earlier the engine upon starting will almost immediately start missing like a vacuum leak or misfiring (?). If you put the car in gear, it almost dies, if the air conditioning is running with the car in gear, it will die most of the time. I have replaced almost all (5) of the 8 COPs, cleaned out all vacuum and breather hoses, replaced the EGR valve, I have not replaced the solenoids for the EGR valve because they are still creating a great amount of suction, and I checked all the hoses for leaks, cracks,etc., and still have the same problem. Engine is no longer throwing OBD2 codes for misfires, but still throwing code (can't remember #) for "catalyst efficiency below threshold bank 1". This code has been issued a couple of times in the past few months, but the car still ran fine. I am at a loss of where to go from here and what to try next. I am looking for some help from other people who may have had this problem or know how to fix it, because it seems I'm just throwing money at the engine and getting nowhere!! Please help!!
Have you checked the vacuum reading? It should be around 20. Then snap the throttle, it should drop to around 2 and jump to around 25. You also could also have a bad or dirty MAF sensor. This is a good start.
I have removed the MAF sensor and cleaned it with sensor safe throttle body and air intake cleaner. As stated above, it didn't appear to be very dirty to begin with, but, I'll try anything!! I cleaned it, reinstalled the sensor, and, no luck. Still sputtering and barely running at idle, when dropped in gear it will still sometimes die. It's still lurching at slight throttle while driving under a slight load (small hill, etc.). So, I tried unplugging the MAF sensor while it was idling, and no real change in engine behavior. The IAC hasn't been replaced yet, but, would it be causing the symptoms listed above even at highway speeds? Thanks for your help so far!!
OK I tried starting the car with the MAF unplugged and it ran about the same, so I plugged the sensor in, and there was no noticable difference. Is that a good thing or bad? Also, while the engine was running (using the term loosely!) I unplugged the IAC and the engine idle increased a little and the problem was still there, so I plugged it back in and the engine speed lowered back to normal levels but still has the same issue of sputtering really badly.
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