2001 VW Jetta, rain-related? P1142,1654,0300,0304,1166,0113

I'm no VW expert, but the drastic change caused by the weather and the /random misfire/fuel trim/intake air temperature codes tell me you may have something going on with the mass airflow sensor.

I suppose I should mention that I bought the cheap MAF sensor. One parts store said I needed to know which one I needed (two choices) and another said you can either pick the $99 or the $199 one. I chose the $99. If you think it's the MAF sensor, should I try the expensive one? I am certain that the last one I had put in was around $175.

Well friend, I can't tell you which one you need because I'm not sure that is the actual problem with your car. What I meant was that the MAF sounds likely, but more investigation is needed. Also, I hope you're getting your MAF from Napa, Carquest or the dealer. Electronic parts from the Zone and Advance are notoriously unreliable. What you really need right now is a way to look at the MAF value on a scan tool. If you intend to do your own diagnostic work you can't go very far without it. There are lots of good ones available for 200-300.00.

FergusonTO35 wrote: Well friend, I can't tell you which one you need because I'm not sure that is the actual problem with your car. What I meant was that the MAF sounds likely, but more investigation is needed. Also, I hope you're getting your MAF from Napa, Carquest or the dealer. Electronic parts from the Zone and Advance are notoriously unreliable. What you really need right now is a way to look at the MAF value on a scan tool. If you intend to do your own diagnostic work you can't go very far without it. There are lots of good ones available for 200-300.00. Thanks for the info! Yeah. I have a factory service manual and the vag-com software and one of these ( http://www.alpha-bid.com/vagusb.html ). Also, I bought the MAF from Napa. The weather turned very cold again and my check engine light went off...and the car is running fine. So strange! Perhaps I'll buy the expensive MAF next time it acts up... I can swap it out in minutes... if it doesn't fix it, I'll return it.

Sweet!! Good luck.

key, I would not waste your money buying a new sensor. I have a 2001 Jetta as well, and I have the exact same issues! I thought I was the only one! The MAF sensor was replaced while under warranty and since then, I have the same issues as you when it rains or is very humid out. Instead of replacing the part over and over, I've just learned to live with it. let the car warm all the way up before you drive and, and leave it in a low gear until the hesitation is gone, then resume driving as normal. Once the engine heats up, it runs fine. Just a suggestion that will save you some $$$.

Sounds like ignition coil pack to me... I had to replace it on my wife's 2003 Jetta and the research I did seemed to show it was a common problem. The plastic housing cracks and when water gets into the cracks it shorts to ground, giving you misfires, rough idle, engine lights etc. An easy way to check is get a spray bottle with water in it and start your car at night, locate your ignition coil pack (it is on the right side of the engine, kind of below the MAF sensor.. just follow your spark plug wires if all else fails) and spray the water on it while your car is running. You might be able to see the cracks allowing the short to occur. It will probably run you around $200 to buy a new one.

jackbooty wrote: Sounds like ignition coil pack to me... I had to replace it on my wife's 2003 Jetta and the research I did seemed to show it was a common problem. The plastic housing cracks and when water gets into the cracks it shorts to ground, giving you misfires, rough idle, engine lights etc. An easy way to check is get a spray bottle with water in it and start your car at night, locate your ignition coil pack (it is on the right side of the engine, kind of below the MAF sensor.. just follow your spark plug wires if all else fails) and spray the water on it while your car is running. You might be able to see the cracks allowing the short to occur. It will probably run you around $200 to buy a new one. Awesome! This give me one more thing to check. I am still having the problem, and this seems like a pretty straightforward diagnostic process. I am DEFINITELY sure now that it is moisture/rain related. It seems to only happen before the car is warmed up, after a rainy night or day. Thanks!

I had to join this forum just for this discussion. I too have had the same problem. It started a couple years ago and I have the same symptoms as you. I changed the ignition coil and that did not fix the problem. Changed the MAF, spark plugs and wires and still had the problem. Finally I replaced the fuel pump and everything was fine... for about a year and 1/2 and now I am having the same issues again. Now, it could be that after changing the ignition coil I still has some other things wrong but who knows. I too am interested in figuring this out. It drives me crazy!! I too think it is moisture related. Why would changing the fuel pump fix the problem and why is it back again? Looking forward to figuring this one out.

VW has a problem with coil packs but they also have a problem with the temp sensors that control how much air and fuel get into the fuel system you can also look at the IAC idle air control valve.

Well, I decided to investigate my Jetta problem a little bit this evening. It's been raining for what seems like weeks, and sure enough my car has been running like crap. Tonight I decided to spray a little water on the engine while it was running. Basically, I was able to pretty much soak everything around the main engine (sorry, I don't know terms). After no problems, I decided to spray the engine directly. The car starting running rough almost immediately. Also, it didn't recover very quickly at all. My roommate seems to think perhaps the water is being sucked into the system some how. I do not believe it is an electrical problem, as this would probably clear up MUCH faster with the heat drying up any moisture... perhaps water IS getting into the engine?

Just updating... I've GOT to figure out this problem soon. I feel like it cannot be good for my car to run so rough when it's been raining. It is absolutely 100% water/moisture related. I can almost guarantee it will happen after a good rain... and won't go away until (presumably) the water around the engine has all burned off. I apologize for not trying out a few things suggested in this thread. I'll do so ASAP and post the results. It's expensive trying to figure this out Not sure if I've mentioned it yet, but it doesn't seem to have problems with snow... just rain.

I think you may being mislead by the diffeence between moisture from the rain and barometric pressure that changes when it rains, the MAF reads engine load and Baro pressure to set fuel trims. To me it stil sounds like you're chasing an issue with cheaper quality MAF'S. I'd recommend only a factory MAF from VW or before making that committment have somebody with alot of experience with VW's and the correct scan tool to spend some time on the diagnosis. Trying to resolve this issue like you said is getting expensive but money is always better spent on expertise then unnecessary, lower quality replacement parts