Hey guys,

I have an 02 a4 1.8t quattro at 82000miles. About a week ago i was traveling from my house to school, about a 4 hr drive. The drive was decent, i had bumper to bumper traffic due to road work so i was stopping and going, and i also drove at about 85 for a while. When i finally got off the highway, at the first red light i stop. As soon as i stop my rpm jumped from about 1000 to 3000 and then back to 1300 and up again to 2500, and so on. Being a rookie at first i thought it was my timming belt so i got home and looked up information about the timming belt. But my car would have stopped working by now if it was. (i havent driven it in about a week) I also thought that it could be the ignition coils or spark plugs, but i changed all of my coils less than a year ago, do they go bad that fast? [COLOR="Yellow"]Also how would i check to find out which coil is the one that is misfiring? I really dont know what the problem is, and i dont want to go to the dealer just to get ripped off..... Does anyone know what these fluctuations could be caused by? Please help mee.

Thanks

 

Maybe your spark plugs? Is it misfiring now?
For the coilpack:
car is on, take one coil at the time, if lets say taking the first one out doesnt shake your car AT ALL, than this would be the bad one.

 

Very similar problem with me. If you find out what it is, let me know. I changed my fuel filter and it went away for a little while then it came back. Really annoying.

 

it is misfiring, now i want to be careful and ive only changed my coils once myself. Would you be able to explain this process in more detail to me?

so basically if i turn my car on it continously misfires.
-by misfire i mean it jumps the rpms up and down without any throttle.

should i leave it on and take out a coil one at a time?
-if i do this my car would be already shaking and misfiring, would it do it to a greater degree? and if nothing happens would it be that ignition coil that is messed up?

Or

should i leave the car off take out a coil turn it on and see if the shaking is worse?


thanks for all your help
p.s. im ******* **** scared to turn my car on LOL

 

Lets say the problem is in coilpack # 4. So u take the first one out, car starts shaking EVEN more... ok... put it back and take the next one out... you need to find the one that doesnt affect your car at all while being not in the place. Dont worry if your car will misfire even more... I drove with 2 bad coils once to the Dealer... You can go either way (car is on/or off ) here is the diy http://forums.audiworld.com/a4gen2/msgs/1003672.phtml
But like i said, if the coil goes bad than it goes bad for sure with flashing CEL and etc...
Maybe u got a vaccum leak? While car is on, open a hood and listen carefully to any unusaly sucking air sound? and inspect it visually, maybe one of the hoses is broken.

 

Or, and with a Vacuum Leak you should also have a CEL, but only if this leak is pretty big.
Also, might be your spark plugs.

 

If it was a coilpack (CPs) you would know it. The CEL would be flashing and the car would be shaking pretty good.

Anyway, the method he mentioned about pulling CPs is based on the car actually shaking violently. If you pull one and it doesn't do anything then that is the one not working right. If you pull it and the car runs worse and shakes even more then that one is fine. I hope that makes sense.

Again, I doubt it's a coilpack. I am going to guess it's a vacuum leak, maybe a fouled or badly gapped spark plug, or possibly a bad MAF.

These are all things you can check on your own. Spark plugs are easy. If you're not chipped, they should be gapped at 0.032" (closer to 0.028" if you're chipped). Fouled is self explanatory (google it and look at pictures).

Vac leaks are a bit tougher to find but there are methods. You can search teh various audi forums for "vac leak test" to find a couple of methods. However, a simple inspection of all your lines should be done first. Those hoses are rubber and can crack easily with time and heat. Look at each of them and inspect the whole lengths for cracks.

The MAF (Mass Airflow Sensor) reads the air coming in and uses that info to ascertain the proper amount of gas to go with it in the cylinder. If the MAF is messed up then you may be seeing the fluctuating RPMs due to bad readings. Before buying a new one, you can try cleaning yours. I'm at 78k and really want to clean my MAF but I'm running fine. I already bought the acetone. There are DIYs on cleaning this, too.

 

heyy thanks for all the advice im going to try this out tomorrow im going to try the coil first, i need to get the wrench to get the spark plugs out, how do i figure out how deep to install them?? Also i just finished fixing a coolant flange leak that was spraying scolding antifreeze all over some tube i want to figure out if that has anything to do with the problem.

 

Coolant leak shouldnt cause any of those probems.
Spark plugs- just dont go to hard