This is a long one...

Okay, first off this is a problem I've posted about already, but it's been a few weeks and I've had more time to troubleshoot. It's very frustrating because every time I begin to narrow it down to something, something else happens that eliminates that as a possibility.

Here are the symptoms.
Upon starting the car it cranks slowly as if the battery is low, then begins to crank faster and faster before finally starting. Then will often die right away unless I give it throttle.

Once it's running the idle with drop to 250-300 and stumble a bit before raising to a steady idle. I put it in gear and it will drop way low again, stumble and then raise again. When driving and coming to a stop it stumbles and drops nearly enough to stall before raising again, though sometimes it will die. Having the AC on doesn't effect this, once the car has had a few seconds to compensate for the added load, it acts the same.

If I turn the key to accesory and don't start it for a few minutes, or turn it off/on a few times to prime the pump (troubleshooting fuel pump) when I try starting it, it acts as if the battery is so low that it will crank very slowly, then slower and slower before finally clicking as if it's dead. The lights will dim and chimes get all screwy like it's truly dead. However, wait 1/2 an hour or so, or even unhook the battery a few seconds and it cranks right up, no problem and even idles fine. Then on the next start, it's back at it again, every time. I don't know of any battery that can die, then suddenly isn't dead anymore multiple times. When the car is running, the amp gauge reads 13-13.5 and holds steady, so the alt is charging fine.

While driving it acts fine, until coming to a stop. No random stumbling under load, no surging or sticking throttle. No backfires at all. NO SES light at all until recently, but that's due to troubleshooting, I'll get to that. I used HPT and scanned it several times with no DCT's. I got one to show randomly but it showed as an OLD code. I went ahead and replaced the O2 sensor it was for to no effect.

I check, re checked, and checked some more for bad grounds or vacuum leaks and found none. I cleaned the MAF and TB. Replaced the IAT, all to no effect. I unhooked the MAF and it did idle fine and seemed to signify that as the problem. Until it began to do it later with the MAF unplugged as well, and this is what set off the SES light, it went off after plugging it back in.

When I tried starting the car after plugging the MAF back in, it cranked all slow again and unlike anytime before all my gauges started going crazy. Also, while running with the MAF unplugged my gas gauge bottomed out at E, then later randomly worked again. This only happened with the MAF unplugged, never before. And still no codes or SES light after plugging it back in. If I unhook the battery for a few seconds it fires right up and idles great, until I try driving it or shut it off and restart. The it cranks slow and idles low.

I'm out of ideas here. Everything I check is either fine, or seems possibly the culprit until something else occurs that's isn't related at all to each other to rule it out. Any ideas?
TPS is fine.
IAC is fine.
Engine temp never goes much above the mid point on the gauge, basically it's normal.
MAF seems possibly bad, but why the sudden random gauge issue, and why the seemingly dead battery that isn't really dead?

 

Intriguing... You might even have multiple issues here.


What kind of transmission do you have? If automatic, have you tried starting the car in neutral instead of park?


What does your voltage gauge tell you? Some of this smells of an alternator problem or issues with the power distribution from it.