I know there's quite a few threads already on misfiring issues but none (to me anyway) seem to be close enough to my situation. Just for some background, my '04 Comp G has 132k mi right now. (131k when this service was done, and had check engine on since I purchased in October due to bad cat)
On May 15th I had someone at a nearby shop that my dad knew/suggested do my oil change and put in Bosch double iridium plugs (I was having some minor starting issues and figured I'd start with new plugs to see if it helped). The next day, I noticed Pumpkin was having REALLY bad misfires during acceleration and going up hills. We took him back to the shop and the mechanic who did the work asked if there was a check engine light on, which there was but that was always there since he needed a new converter. We were hoping maybe there was just a loose plug wire or something since he just worked on them...right? Well he said it's not possible because that would show up in their scan tool (not sure if that's true as I'm not too familiar with them). He said it was just because of the bad cat, engine wasn't getting enough air and whatnot.
So... we ordered a new OEM fit catalytic converter and had it replaced on the 30th by someone at a different shop that specializes in exhaust (but mainly were charging less than this dude). Maybe about two days later the misfire seemed to improve - the car isn't stuttering and struggling to accelerate nearly as badly as before, and the check engine went away. Yay, but still not really yay.
I want to say maybe two weeks ago we went somewhere else to see if they could pinpoint the culprit and we were told we needed a new MAF sensor and ignition control module (because I've been having hard starts - engine would sometimes turn over but then appear to want to die, and needed to either give it some gas or shut it off and try again a couple of times). They said they cleaned out the MAF sensor a bit but that I would need a new one anyway. We ordered a new one (well not brand new but still functional) and not really much improvement from there either. I haven't gotten to the ICM yet because at the moment I can't afford even the cheapest I can find at around $65.
Now I just wanted to add that two separate times now when getting on the freeway and having the usual misfire(s) during acceleration on the on ramp, I did get a flashing check engine light once the misfire subsided; so I did have to pull over and shut the engine off for a couple of seconds. I noticed today while getting on the freeway the misfire occurred as usual, but I noticed maybe five seconds into it you could feel one of the cylinders snap out of it and the engine regained some power - but not completely. Again the flashing check engine light began after the misfires subsided, but this time before being able to pull over the check engine went away by itself within a few seconds.
So...I'm in the process of finding some throttle body cleaner so I can clean it out and see if that helps at all..but I'm not too hopeful. I've also tried checking in the case of the hard starts to see if I can hear the fuel pump whine when turning the key to the On position but not cranking it - however I can't really make out the sound of it priming unless its thanks to the chime every time I put the key in that doesn't shut up soon enough for me to listen closer. I do know that the previous owner had bought a new fuel level sensor two years ago, so I don't know if the fuel pump in general could be having other troubles :/
Aaand speaking of fuel level, I have also noticed some time ago that the fuel gauge behaves a little odd in my opinion... I've had times where I drive around for a bit and when we come to a parking lot and park for a while, engine still running, the fuel gauge will slowly start creeping up a bit and go a couple of notches fuller (I've seen it go from 1/4 of a tank to just one notch away from half a tank). I have no clue as to whether or not that is normal or one of the symptoms of whatever issue Pumpkin is having. I know that my mom's Bonneville definitely has something up with the fuel system as you hear a loud compressor sound coming from the pump almost all the time kicking in, and the fuel gauge definitely does not accurately mark the fuel level. (Maybe when you first start the car it will show you the true fuel level, but once you put it in drive and move a bit it will go straight to either full or empty).
Anyways, this is one of the few things bugging me lately that I can't seem to figure out. It sucks having what was once a fun supercharged engine that now feels like the exact opposite. Can't even get onto the freeway without being an embarrassment to the GP family...
I do believe if I remember correctly from checking the service records the previous owner gave me, they bought the wires and coils that are currently in the car sometime around 2010. They're by MSD and funny thing is when I looked up the part numbers on their website and even called them, I found no indication that these coils and wires were actually designed/tested for this year and model. What just bothers me is that the only problem I ever had before was the hard starts, never any actual power reduction/misfires before simply having the spark plugs changed. Unless like I thought the guy screwed up one of the wires or something while he was working on it...
Originally Posted by GTPpower
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(not to say everyone on the forum hasn't been helpful, because you definitely have)
