3800 needs some help diagnosing....

phat_ridegt

TCG Elite Member
Sep 16, 2007
3,351
2
Ottawa
Heres the situation. The car is a 2000 gtp. Mods are in my sig, but I will list them. XP, new wbs ic, togs, stage 4 m90, STOCK tb and maf, among other tid-bits. When I start the car when it is cold, is runs fine. It doesn't act up until the car is at operating temp (drilled 160 stat), and you shut it off, and restart within an hour or so. When i start it, it will cough and stutter, like it has a HUGE vacum leak, the same thing it would do when you pull the vacum boost line off while it's running. It will then come out of it, and idle fine, the do it again about two more times, and then it will run like a champ until you shut it off, and restart.

I have checked, and check, and triple checked for any vacum leaks, including at the ic, s/c, tb, fuel injectors, evap system, and anywhere else I could think of. I do not think it is a vacum leak issue. The ltft idles around +10-14, and stays around 0 when the TP% is increased. The IAC's are steady at 58-60, but when the car acts up, it jumps to 100-110, and then drops back down when it comes out of it.

I took the purge solenoid off today to see if it was leaking/stuck/inop, and with the off and the lines capped, it still did it. When i went to reset the SES light, i noticed it had a MAF code as well. it was a history code, i believe it was a p0101 which is a genaric code for performance. so i unplugged the maf when it was acting up, and it came out of it very quickly, and was fine. now i understand it's just going into open loop...so here is my conclusion:

After checking for B+, ground and a 5v reference (which are all good, no resistance), so it is either in the tuning (not sure what to look for in the maf tables) or the maf sensor is bad. I dont have a spare maf, so i am trying to source a cheap one to see if it is indeed the problem. I find it hard to believe though that this just 'went out' for two reasons, one, it didnt do it before the i/c was re-installed and the car was tuned (which i am confident neither of which are the issues), and two the maf reads correct hz, and g/s while it is acting up.

Does anyone have ANY suggestions on what else to try? I'm stumped.

CLIFF NOTES: car has a bad sputter/cough upon start up at operating temps~
 
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imported_Ron Vogel

Guest
I think I see this more clearly now.

Fist off, the car runs off the MAF at strt-up, then switches to the 02 once the PCM thinks the 02 sensor is heated enough. I had this very same issue and ended up replacing the front 02 sensor connector on the harness side to fix it. The weatherpack connector went bad, and it would trap moisture a lot. The car would run great for about a minute, then like crap for 5 minutes, then fine again.

This would make a lot of sense as I washed your motor to clean the oil off of it, and the fact you have an A/F pigtail on there. I've seen several people with problems from them, and I generally disconnect them before going out scanning a car ever since.
 
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imported_Ron Vogel

Guest
Originally posted by phat_ridegt@Oct 21 2006, 08:58 AM
so you already replaced the o2 connector on this car?  hmmm, i thought of that also....the o2 is stock w/ 90k, i suppose it could be going bad as well.
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I didn't replace the connector on your car, but disconnected the a/f hook-up. Pull the connector apart and look for moisture or this greenish slime. I had to wipe mine out and leave it apart for several hours to dry and it helped for awhile until moisture got back in it.
 
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