CarTalk.com Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Reoccurring Mystery Misfire in 2004 Jetta

Recently (5 weeks ago), my 2004 Jetta misfired, which caused the car to shake very noticeably, especially at lower speeds or while idling. The misfire was accompanied by the smell of fuel on the driver side and triggered the check engine light to flash. I took it to the shop (a VW dealer). They ran diagnostics, found it signaled a misfire (but no other major issues/sensors) and told me it was due to the spark plugs/wires. I was dubious, as they were not too old, but I allowed them to replace them anyway, as they assured me this would fix the problem. Just this week, however, another misfire occurred, also accompanied by the smell of fuel and shaking. This time, the check engine light remained on (constant) for 2 days, and on the third day, it was off. I brought it back to the same shop to try to figure out the real cause of the misfire, which obviously was not the previous spark plugs. My city gas mileage has also decreased over the past month - down to about 20-21 mpg from 23-24. Does anyone have any idea what could be causing such a reoccurring misfire without signaling an issue with a sensor or other part? Thanks!

Does this thing have Turbo?

Sorry for omission - it is a 2.0 liter engine - no turbo.

Did they tell you what the engine codes were?

They only thing they told me previously was the the engine code signaled a misfire. As they are a dealership and generally give me a laundry list of other repairs each time I go in, the fact that they did not mention additional codes makes me think that the only issue signaled by the engine light was the misfire.

The decreased gas mileage could be a clue. Maybe you have a sticky injector and it dumps too much fuel into the cylinder head. That could cause a misfire and bad gas smell.

This may or may not fix it but it is certainly cheap as you can try it yourself:
Buy some Techron gas additive and put it in when your car is about at 1/4 level. Drive it around for a bit before filling it up. Sometimes you may need to perform this a couple of times before you actually feel the result.
Techron is one of the better fuel system cleaning additives. It may fix it.
If it doesn’t, all it will set you back is $10 per treatment.

Thanks - that is definitely worth a try!

It sure is. I’ve seen rough idling engines run so much better with just one bottle.
Report back, should that not work.

Oh, Techron can pretty much be bought anywhere (advance, pepboys, autozone, etc) so it is readily available.

No Mention Of A Volkswagen Service Campaign ?
From My Experience A Campaign Is Like A Recall, But The Manufacturer Voluntarily Repairs Cars, Rather Than The Government Requiring it.

There are several Volkswagen Technical Service Bulletins written for VW technicians for dealing with misfires in many models and model-years (including 2001-2008 Jettas with gasoline engines). Some of the information addresses problems that persist even after replacing ignition coils as outllined in campaign(s) for fixing specific vehicles.

The misfire codes found cover all cylinder P0300 random and multiple and individual cylinders P0301- P0312.

Perhaps somebody at Volkswagen needs to do a little homework to see if there is a campaign that has not been completed on your car (there should be a sticker 28F/P1) or bulletins that pertain to this. It’s possible that it won’t cost you anything or very little.

CSA

Oh, wow. No, there has been no mention of this. I will ask them later when they check in.

It Will Need To Be Determined If The Ignition Coils On Your Car Are Faulty. Apparently There Has Been Some Problems With Certain Ones On These VWs. You’ll Also Have To Have It Determined If Your Vehicle Is One With Possibly Defective Parts.

You Can Search The NHTSA (National Highway Traffic Safety Administration) Site And Find These References To TSBs.
They all pretty much cover the same models/years, so I didn’t print that each time.

Service Bulletins Summary
Make / Models: Model/Build Years:
VOLKSWAGEN / BEETLE 2001-2007
VOLKSWAGEN / EOS 2006-2007
VOLKSWAGEN / GOLF 2001-2007
VOLKSWAGEN / GTI 2001-2007
VOLKSWAGEN / JETTA 2001-2007
VOLKSWAGEN / PASSAT 2001-2007
VOLKSWAGEN / PHAETON 2004-2006
VOLKSWAGEN / R32 2004-2007
VOLKSWAGEN / RABBIT 2006-2007
VOLKSWAGEN / TOUAREG 2004-2007

Service Bulletin Number:
SAC-28F3/P1-REV
NHTSA Item Number:
10036496
Summary:
VOLKSWAGEN: GASOLINE ENGINE VEHICLES INSPECT, AND IF NECESSARY, REPLACE IGNITION COILS. VEHICLES AFFECTED BY THIS ACTION MAY HAVE IGNITION COILS THAT COULD MALFUNCTION UNDER CERTAIN CONDITIONS. MODELS PASSAT AND WAGON; GOLF; GTI; JETTA AND WAGON; NEW BEETLE AND CONVERTIBLE; PHAETON; EOS; RABBIT, ETC. *PE

Service Bulletin Number:
SB-28F3
NHTSA Item Number:
10033207
Summary:
VOLKSWAGEN: VEHICLES MAY HAVE IGNITION COILS THAT COULD MALFUNCTION UNDER CERTAIN CONDITIONS. IF THIS HAPPENS, THE MALFUNCTION INDICATOR LAMP (MIL) WILL ILLUMINATED TO LET YOU KNOW THAT THE VEHICLE MAY EXPERIENCE SOME DETERIORATION IN PERFORMANCE. IN SOME CASES, A MALFUNCTIONING IGNITION COIL MAY CAUSE A VEHICLE TO EXCEED FEDERAL AND/OR CALIFORNIA EMISSIONS STANDARDS. NO MODELS LISTED. *PE

Service Bulletin Number:
SA-28F3
NHTSA Item Number:
10033216
Summary:
VOLKSWAGEN: (REVISED) VEHICLES MAY HAVE IGNITION COILS THAT COULD MALFUNCTION UNDER CERTAIN CONDITIONS. IF THIS HAPPENS, THE MALFUNCTION INDICATOR LAMP (MIL) WILL ILLUMINATED TO LET YOU KNOW THAT VEHICLE MAY EXPERIENCE SOME DETERIORATION IN PERFORMANCE. IN SOME CASES, A MALFUNCTIONING IGNITION COIL MAY CAUSE A VEHICLE TO EXCEED FEDERAL AND/OR CALIFORNIA EMISSIONS STANDARDS. 2001-2007 PASSA/PASSAT WAGON. *PE UPDATED 8/9/10. *PE UPDATED 11/8/10. *PE UPDATED 12/8/10. *PE UPDATED 2/28/11. *PE UPDATED 3/21/11. *PE

link:

Perhaps a call to another dealer or two and speaking to a Service Manager/Director or Volkswagen Corporate could shed more light on a possible service campaign covering the expense of a repair.

Is this a small sized dealer ?

CSA

Thanks! It is a pretty big dealer. I saw on VW’s website where you can enter the car’s VIN and check for such campaigns or recalls, and I will ask that they do that. I had the ignition coils replaced 3 years ago and the car recently (Oct 2012) passed its emissions test.

I just picked my car up and they found it was a wire that connects to and powers the ignition coil. This wire was, in fact, on a VW service bulletin and they performed all of the work for free! I hope this solves it!