So here's the problem that I've been having with the Fire.
Starting the car on a cold start, the RPMS start up at around 2k, after 10 seconds it settles down to 950 (RPM should be around 1200 on cold start)
On a cold start, as the car gets to a certain temperature (about 120*), it seems that there is a fuel cut and the idle tanks and goes real rough, almost like its being starved of fuel. I've replaced the TPS, IAC, front O2 sensor, checked for vacuum leaks (none)... ignition coils check out (spark at all 6 cyls)
When the temp gets a little farther up (135*) and I keep the RPM's up some the idle smooths out (kind of... it fluctuates between 900-950).
I set the ECM back to stock values, less the auto-trans stuff, rear O2 and EGR (since I don't have those hooked up), and the problem still persists.
Any suggestions? I don't know if this is doing any damage (doubtful) and it certainly is irritating.
Engine and ECM are 2k1 Grand Am
I can get a datalog tomorrow if that will help
when I did mine I had 2 issues similar--
I had to replace my MAF- was probably old or dirty or whatever happens to them
2nd- changed the fuel pump- my mechanic friend checked and found out the j-body fuel pump pressure was lower than my donor (3100 g/p) pump pressure- worked for me-- hope this helps. jb
I was kind of thinking CTS problem. Are you using the actual pcm reading for your diagnosing or do you have an aftermarket one?
That is what i was originally thinking but the MAF sensor makes sense too, especially if your using an oil air filter, Sometimes the oil gets on teh sensor and attracts dirt and stuff, causing poor readings. But usually is accompanied by poor throttle response.
Can you still retrieve diagnostic codes?
01 cav w/01 3400 gam gt 4t45e
I have a K&N style filter, but its a dry filter. MAF is new, only 7500 miles on it... one that came with the engine was in a puddle, so that got tossed LOL
I'm using the stock ECM, and the only codes that are throwing are
P0135
P0403
Which is odd, since the O2 sensor gets a reading and was just replaced last month. I bypassed the main harness with wiring just for the O2 sensor since it was miswired originally.
I did notice that during the data log that about 4 minutes after startup, the fuel ratio starts creeping towards rich whatever the fuel trim is doing, that drops out... Also my water temp gauge is reading 20* colder than what is actual so the temp values in the top post, add 20*
I'll see if I can find a MAP for cheap and change that over though
can you manually adjust the egr recirc and the iac with your scanner??
Yes to the IAC, no to the EGR (has been removed and there is no recirc controls available)
I wouldnt worry about the 403, its just letting you know that you blocked off the egr. I welded up one before and got the same code. It was a necessary cheap fix at the time.
If I were you I'd get another O2 sensor, sounds like its sticking when it goes into closed loop fuel. If you can turn off closed loop fuel in Hp tuners, try that first. If you have another cavy sensor to try it will work. I know you said you changed it not too long ago, I would still swap it out first.
Your MAF sensor should shoot a code, or kill the motor if you tap on it while runnning. Doubt thats the prob.
01 cav w/01 3400 gam gt 4t45e
Quote:
If you can turn off closed loop fuel in Hp tuners, try that first.
Turned off closed loop, runs great now. Hmm.... I'll just leave it alone and call it good.
Alrighty, now you need to find out if its the upstream or downstream, HO211 is up and HO212 is down. Watch the reading when it goes into closed loop, look for a negative mili volt reading when it screws up. Upstream would be the first one that I watch.
Or you could leave it in open loop I guess.
01 cav w/01 3400 gam gt 4t45e
So kardain, I guess your driving it alot more lately?
2002 Cavalier "LS Sport"
