I have a 2001 GT with the 4 speed auto and 127,000 miles on it.
The car has always (since I've owned it - for roughly 20,000 miles) had a slight miss but just recently started missing a lot worse.
It seems that when the car is cold, it runs pretty good, and the miss really doesn't kick in until the engine is nice and warm. Its almost as if the miss is only in one part of the RPM band, and when I get on it, seems clears up (for the most part) until the car kicks into overdrive (back down to the magical RPM range) where it starts cutting out heavily again.
I've done quite a few minor things to try and clear it up.
1) New platinum plugs this past February, and cleaned the throttle body -- the car started missing then too, but the plugs cleared it up.
2) Fuel system cleaner periodically -- First in February before the plugs, then again in May when the miss reared its ugly head for the second time and then twice again now with this latest spell. The car actually ran so good the last time I added cleaner that I thought I had solved the problem.
3) 8 new coil boots -- I thought moisture might be getting in.
4) 2 new coil packs -- I did the 'turn your car on and unplug each coil to see if it changes the idle' thing and while NONE of the coils seemed bad, two did seem weak. So i switched them each out one at a time to see if I could isolate the miss, but eventually replaced both of them. The plan was (maybe still is) to replace the other 6 when I have the money. But if they're working fine, should I?
5) I had been noticing that the car was idling a bit weird, so I took the ICV off and cleaned it. I also cleaned the throttle body again, cleaner the MAF sensor and re-oiled the K&N filter. The car is idling MUCH better and, once again, the problem seemed solved for about a day.
6) After messing with ignition so much, I suspected the fuel system and replaced the filter. I don't think its a fuel pump problem because the car is idling so well and it does fine through the RPMs except in that one range.
7) Not that it matters much, but I also replaced the battery and alternator.
The car has recently been making a weird noise right after I fire it up. It's like a moan or something and usually happens one time. My gut instinct was a vacuum leak. Tonight I looked at all of the hoses (unless there are hoses under the car -- I don't have the tools to do that right now) and felt around them while the car is running. I also thought the PCV valve might be causing problems, but I'm not losing any oil and it still sounds (rattles) fine.
So my question is: where should I go from here? 1) Pull the plugs and double check them again. 2) Drop the money on more new coils and hope that it fixes the problem even though none of them seemed bad. (the 'no miss at cold' and miss when the engine warms up leads me toward this) 3) Drop the money on a new ICV valve and hope that fixes the car, despite it idling fine (least likely culprit IMO) or 4) Look somewhere completely different like the EGR valve?
ANY help is greatly appreciated.
EDIT: Forgot to mention, the only two mods to the car are the K&N filter and SLP Loudmouth II mufflers that were installed roughly a year ago.
The car has always (since I've owned it - for roughly 20,000 miles) had a slight miss but just recently started missing a lot worse.
It seems that when the car is cold, it runs pretty good, and the miss really doesn't kick in until the engine is nice and warm. Its almost as if the miss is only in one part of the RPM band, and when I get on it, seems clears up (for the most part) until the car kicks into overdrive (back down to the magical RPM range) where it starts cutting out heavily again.
I've done quite a few minor things to try and clear it up.
1) New platinum plugs this past February, and cleaned the throttle body -- the car started missing then too, but the plugs cleared it up.
2) Fuel system cleaner periodically -- First in February before the plugs, then again in May when the miss reared its ugly head for the second time and then twice again now with this latest spell. The car actually ran so good the last time I added cleaner that I thought I had solved the problem.
3) 8 new coil boots -- I thought moisture might be getting in.
4) 2 new coil packs -- I did the 'turn your car on and unplug each coil to see if it changes the idle' thing and while NONE of the coils seemed bad, two did seem weak. So i switched them each out one at a time to see if I could isolate the miss, but eventually replaced both of them. The plan was (maybe still is) to replace the other 6 when I have the money. But if they're working fine, should I?
5) I had been noticing that the car was idling a bit weird, so I took the ICV off and cleaned it. I also cleaned the throttle body again, cleaner the MAF sensor and re-oiled the K&N filter. The car is idling MUCH better and, once again, the problem seemed solved for about a day.
6) After messing with ignition so much, I suspected the fuel system and replaced the filter. I don't think its a fuel pump problem because the car is idling so well and it does fine through the RPMs except in that one range.
7) Not that it matters much, but I also replaced the battery and alternator.
The car has recently been making a weird noise right after I fire it up. It's like a moan or something and usually happens one time. My gut instinct was a vacuum leak. Tonight I looked at all of the hoses (unless there are hoses under the car -- I don't have the tools to do that right now) and felt around them while the car is running. I also thought the PCV valve might be causing problems, but I'm not losing any oil and it still sounds (rattles) fine.
So my question is: where should I go from here? 1) Pull the plugs and double check them again. 2) Drop the money on more new coils and hope that it fixes the problem even though none of them seemed bad. (the 'no miss at cold' and miss when the engine warms up leads me toward this) 3) Drop the money on a new ICV valve and hope that fixes the car, despite it idling fine (least likely culprit IMO) or 4) Look somewhere completely different like the EGR valve?
ANY help is greatly appreciated.
EDIT: Forgot to mention, the only two mods to the car are the K&N filter and SLP Loudmouth II mufflers that were installed roughly a year ago.