Ok this has been doing this for about a week and has just gotten worse. About a week ago my car started jerking (seems like a misfire as the RPMs drop really quick as if I'm tapping on the brakes) slightly with the A/C on while driving. It would only do it at a constant speed at first. Now that I thought it was the A/C compressor that was going out I started feeling it with the A/C compressor off. I would only jerk every once in a while while cruising. It just got worse as it started doing it all the time. Now its really bad after I take off from a stop light. It won't do it free revving in neutral so its a load only issue. It does it REALLY bad with the A/C on which makes since because the engine is under more of a load with the A/C on. My idle is perfect except it spikes when the A/C is on and the A/C clutch is cycling on and off. I just bought some OEM AC Delco plugs and new wires but it still does it. The previous owner couldn't screw in a spark plug I guess because #2 and #4 are cross-threaded and will only screw in about halfway. Might I remind you that I drove it for a week like this and it didn't do anything. I get no CEL for anything. I am so lost as of now. Could it be a fuel filter maybe? All it does is jerk randomly while accelerating or cruising. Doesn't do it while idling and barely does it while heavy accelerating.
Id start with getting the plugs all the way into the head. how do they look after driving it with this problem? what color? any deposits?
might be the coilpacks as well, how many miles on the car?
It sounds a lot like you fuel pump is starting to go out. My VW did exactally what your talking about, and replacing the fuel pump fixed it. Cars usually do what your talking about when the fuel pump starts overheating from age or use, then it gets worse over time until the car isn't drivable anymore. Try replacing your fuel filter if you havn't already, and listen to see if you can hear the pump when the car is running. If you can hear a definate high pitched wine coming from the tank over the sound of the car running (standing or kneelin next to the car), it means that the pump is working too hard.
Ok now it hasn't been doing it all night and I haven't touched the car since so I don't know what it could be.
Ok I have been driving it a little more and the symptoms have kind of changed.
1. Car is perfect at idle. It idles which looks like 600-700.
2. Car only jerks while taking off from a light under LIGHT acceleration. Maybe 0-40% throttle. Any more throttle and it doesn't buck or jerk. Does it worse when A/C is on so its a load issue only. Still trying to find a 16mm flare nut wrench to change it but fuel filter looks rusty so it looks old. But wouldn't a clogged fuel filter make it buck at a higher load too when put 50% or more throttle?
3. Car feels fine under heavy acceleration.
4. It jerks and bucks RANDOMLY. Sometimes its a harder jerk but they are soft ones usually. There is no pattern with them and it isn't constant either. It just does it when it wants to. And I still don't see a CEL. I thought that it could be a vacuum leak but my idle is fine.
Sorry if this ends up being a stupid and easy diagnosis but Since there is no CEL then a mechanic will most likely take a wild guess and I will end up paying for a lot of parts that are not the problem.
Can anyone help me at all? I have pretty much given up on this POS and about to go back to a DSM
Wouldn't a clogged fuel filter or cat make it jerk at higher load and RPMs as well? Since more fuel and more exhaust is required for both of those and it doesn't happen at a higher load or rpms so I don't see how it could be those.
Ok a buddy of mine used his Tech 2 flash scanner on my car today and all I have to say is wow. It was misfiring on cylinders 2, 3, and 4 when driving but not noticable when idle. And then we turned the A/C on which is low on freon and it made it 100x worse. It was misfiring like crazy and after about a 3 minute drive with the A/C on my gauge cluster just shut off and then turned back on as when first starting the car. Didn't affect the motor at all though. He said this is the first car he has seen this bad and not one CEL. I'm starting the think the PCM is toast. Anyone have another answer? Its going in the shop on monday.
