I have an 02 with a 2.2 OHV non-flex A/T base model.
I have been having issues with it running like crap intermittently. All my research has led to it,s the alternator or bad grounds.
If i unplug the 4 pin connector at the alternator it runs just fine. Plug it back in and it may idle like crap or not, it may run like crap down the road and fall on it's face with absolutely zero throttle response other than you can hear the engine sound change with it floored from deleting the intake resonator but the car is still slowing down as if you shut the key off, while it;s doing that sometimes it'll backfire while spitting and sputtering. Again, pull over and unplug the 4 pin alternator connector and she clears up and will run up 6k rpm no problem at all.
I have upgraded from the CS130D alternator to the AD244 145 amp, I also have 1/0 wire added to the alternator positive post to battery as well from battery ground to body and engine. This is the 3rd one of those I am on since having this problem thinking it was a bad diode issue in the rectifier bridge leaking to much AC voltage and upsetting the PCM/ sensors. Still having the same issue, so I bought new battery terminals to get a fresh connection to all my wires. still having the same issue.
As I type this the car is in the bay running with the alternator plugged in and charging above 14 volts with no load other than engine running and cooling fan running (Stock cooling fan). It has ran fine and ran like crap while its been sitting here and more so when the cooling fan kicked on pulling a load on electrical of course. Unplug the fan relay and it would clear up, but not the fan is still on and it's running normal.
Something else I noticed is I have my MAC (Fluke) DVM reading voltage and recording max it has only gone up to 14.7 volts, but our shops Midtronics PBT-300 battery tester will read voltage and periodically go in to protection from over voltage as in more than 15.??something volts (I am not sure which tool to trust as the PBT-300 has been dropped a few times but does seem to function normally). All this supposed voltage swing/spiking is happening while the car is running just fine. I have also measured AC voltage between alternator and battery, It is 0.02 something and sometimes hits 0.03 something. Doesn't seem to matter if the car is running good or bad. Alternator output is just under 30 amps and will go to around 60 amps with everything but the radio and reverse lights on (High beams, cooling fan, HVAC blower high, Hazards flashing, engine running.
I am an auto tech (no not a lube tech) with about 7 years of on job experience and this issue just has me, my boss and all other automotive related friends/family stumped. It is my personal daily driver and this has been going off and on for a little over a month, first alternator change from #1 AD244 AC delco, to Oriellys AD244 re-man seemed to fix it but here the problem goes again, after getting the re-man warrantied which brings us to AD244 #3 that is currently on the car and still having the same issue. Also earlier this year it did get plugs wires, fuel pump module, fuel filter and air filter, swapped coils for known good coils I had in my toolbox with no change to issue. I have not changed the ICM as I don't have a spare to just throw on and try out as the one on the car does test good according to alldata as did the coils but I had spares.
Sorry for the long post but I wanted to give as many details as I can recall so that hopefully somebody can help as I am just lost at this point and hoping I am not the only one that has had this issue. Many thanks to any help you all give.