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2002 Jetta Misfiring/Catalytic converter problems


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Nebulium
Novice

May 31, 2013, 4:07 PM

Post #1 of 10 (5693 views)
  post locked   2002 Jetta Misfiring/Catalytic converter problems  

Hey everyone, I've got a 2002 VW Jetta 2.0L that just started giving me some problems. I started driving up a steep hill and the engine started sputtering and the accelerator was fairly unresponsive. After I pulled over and checked the engine I noticed it had a pretty bad smell to it. I hadn't drove far so I turned around and coasted down the hill and drove the rest of the way home, maybe 2 miles round trip tops. The rest of the drive, the engine worked fine, it maybe sputtered once or twice, but the accelerator responded fine.

After hooking up the scanner I got P1296, P0420, P0300 and P0304. The first was for the coolant sensor I believe, the second was for the catalytic converter not working well enough and the last two were for random misfires and cylinder 4 misfiring respectively.

What I was looking for was some opinions on what would be the best course of action. I assume that I should replace the sensor and cat, but I wasn't so sure about the misfiring, I plan on checking the spark plugs since they are kind of old. But I was wondering if there could be some link between the misfiring and the cat or the coolant sensor. I'm pretty strapped for cash so if I could avoid replacing some parts for now I would be really relieved.

Thanks in advance.


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

May 31, 2013, 4:23 PM

Post #2 of 10 (5686 views)
  post locked   Re: 2002 Jetta Misfiring/Catalytic converter problems  

You should focus on the misfire codes and coolant sensor code first. Don't worry about the catalyst code until you find out why the misfires are showing up.

How many miles since your last tune up? What is the mileage on the engine?





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


Nebulium
Novice

May 31, 2013, 5:29 PM

Post #3 of 10 (5677 views)
  post locked   Re: 2002 Jetta Misfiring/Catalytic converter problems  

Oh yeah, sorry I forgot. The mileage is 155,000 and I'm not sure when the last tune up was, it's a pretty new car (to me anyways.)


Nebulium
Novice

Jun 3, 2013, 3:58 PM

Post #4 of 10 (5624 views)
  post locked   Re: 2002 Jetta Misfiring/Catalytic converter problems  

What would yo suggest to find out the cause of the misfiring? I am definitely checking the spark plugs as soon as I can, I'm just not sure of what else it could be.

Thanks


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Jun 3, 2013, 4:50 PM

Post #5 of 10 (5619 views)
  post locked   Re: 2002 Jetta Misfiring/Catalytic converter problems  

Anything that affects the combustion process in a cylinder from occurring or occurring properly will cause a misfire.

So that means anything such as fueling, ignition, or mechanical problems will cause misfiring.

You have to isolate which system would cause the misfire to occur and also determine which cylinder(s) the misfires are happening in. Usually the ignition system is the first place to start because ignition problems are fairly common reasons for misfiring.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Jun 3, 2013, 4:51 PM)


Nebulium
Novice

Jun 5, 2013, 2:35 PM

Post #6 of 10 (5598 views)
  post locked   Re: 2002 Jetta Misfiring/Catalytic converter problems  

I was finally able to start working on it today and I noticed that the vacuum hose that goes from the Fuel pressure regulator to the intake manifold was completely torn! So I replaced it, cleared the codes and started it back up. I tried revving the engine a bit and it seems to be going smoothly, and the codes haven't come back (aside from the coolant sensor, which I'm about to change anyways.) Could that have been the entire cause of the problem?


Nebulium
Novice

Jun 7, 2013, 1:38 PM

Post #7 of 10 (5577 views)
  post locked   Re: 2002 Jetta Misfiring/Catalytic converter problems  

Well I started it up again today (a much colder day than when I did the work on it last) and the misfiring has come back. Luckily the only code that has returned is the number 4 cylinder. I've replaced the #4 spark plug though so I doubt that is the problem. Also once I let it warm up it started running a bit smoother, not like normal, but definitely not as bad.


(This post was edited by Nebulium on Jun 7, 2013, 1:49 PM)


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Jun 7, 2013, 6:02 PM

Post #8 of 10 (5566 views)
  post locked   Re: 2002 Jetta Misfiring/Catalytic converter problems  

You should solve the coolant temperature sensor problem. That is a critical sensor input.

As for the misfire, how old are the plug wires? Plug wires do wear out. Also was there any oil down in the spark plug wells?





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


Nebulium
Novice

Jun 17, 2013, 7:21 PM

Post #9 of 10 (5520 views)
  post locked   Re: 2002 Jetta Misfiring/Catalytic converter problems  

Sorry for not replying sooner, I guess there is something wrong with my email. Although it took me a while to finally be able to, I tested the ignition coil pack and the resistance was really off on the last pin so i got a replacement and so far that seems to have solved the problem. Thanks for the help!


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jun 18, 2013, 1:06 AM

Post #10 of 10 (5511 views)
  post locked   Re: 2002 Jetta Misfiring/Catalytic converter problems  

For now consider this solved I guess. Locked to prevent spammers and can re-open upon request,

T







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