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Post your VAG-COM errors?
Does it run better after running the engine for about 20+ minutes?
When my TPS was failing, it was less likely to stall/run roughly when it had been driven 20+ minutes. IMO, that when the sensor warmed up via the heat rising from the headers resulting in better electrical contact.
 

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Discussion Starter · #22 ·
Re: (MastaVR6)

The only code I have is a perpetual cat efficiency code (16804).
The idle is the same after an hour on the highway as it is a few minutes after starting the car. The idle is actually rock solid at 680 according to VAG-COM. Granted the resolution of the VAG is only 40 RPMS, but it never fluctuates from 680 (meaning that the idle is constantly between 660 and 700). The car drives great. The only problem is a slight "jerk" in the engine at idle. It could be a number of things I guess, vac. leak, fuel delivery problem, worn motor mounts, a bad plug, etc. I don't think the problem is serious - it's more of a frustration. The idle used to be so incredibly smooth and now it's not anymore. Maybe I'm asking too much from a car with 144k miles where everything is original (except the stuff replaced during routine maintenances).
Cleaning the TB was a first attempt at solving the problem.
 

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Re: Anyone ever clean the throttle body on their MKIV? (VgRt6)

Something very important to do when cleaning either type of TB (cable or DBW) is to make sure when spraying the TB with cleaner. All MKIV TBs' have electronics inside them, the DBW more. I've taken TBs' apart before and if you remove the plastic cover on the side you will see potentiometer contacts. and fine 'swipers' that make contact with the potentiometer tracks. If these get damaged in any way the TB is trashed. I have seen people clean the TB and the cleaner penetrated into the electronic section of the TB and destroy it. Have also seen after cleaning the TB, the car would idle at 1400 RPM until the cleaner was burned through the engine that had penetrated into the electronic portion of the TB. I recommend that when you clean the TB, position it where the plastic cover end of the throttle body (the side with the electrical connector ) faces skyward. Don't oversaturate the TB and feel you need to use a lot of the cleaner. When you clean the TB you are trying to remove deposits on the throttle blade, the venturi and the throttle plate shaft bushings.
VgRt6......I think there isn't anything wrong mechanically with your engine, it's something electrical.
 

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Discussion Starter · #24 ·
Re: Anyone ever clean the throttle body on their MKIV? (4string)

Quote, originally posted by 4string »
I recommend that when you clean the TB, position it where the plastic cover end of the throttle body (the side with the electrical connector ) faces skyward.

This is exactly what I did. I know there are seals to help prevent contamination of the electronics, but I didn't want to take any chances.
Quote, originally posted by 4string »
VgRt6......I think there isn't anything wrong mechanically with your engine, it's something electrical.

I've been leaning towards this conclusion too. I think it's either a coilpack/wire/plug problem or a bad/loose ground somewhere. I also thought it might be a fuel delivery issue, but the engine is only like this at idle. At increased RPMs it's smooth as butter.


Modified by VgRt6 at 10:20 PM 11-10-2003
 

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Discussion Starter · #26 ·
Re: Anyone ever clean the throttle body on their MKIV? (4string)

I was planning on doing that a next step, but I have the flu and am stuck on the couch watching TV all day.
I'm going to try it tomorrow if I feel better.
 

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Discussion Starter · #27 ·
Re: Anyone ever clean the throttle body on their MKIV? (VgRt6)

The thing I don't understand is, if my problem was electrical, why would it only show up at idle? Wouldn't the problem also exist at higher RPMs too? Also, there are no misfire codes stored. The jerking kind of feels like a mini misfire. I had a cracked coilpack about 10k miles back (fixed with epoxy) so I know what a full misfire feels like. The jerking at idle is not nearly that bad, but is still enough make the engine move a good bit and shake the car a little.
I also think it might be time for a can of BG44K. The fuel system has only been treated once in the 144k miles it's been working and that was just one bottle of Techron fuel injector cleaner a while back. Maybe one of the injectors is partially clogged, causing a slight stutter.
 

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