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Volkswagen Jetta, Golf, GTI: 1993-1999, Cabrio 1995-2002 (A3) Throttle Body Problem?


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Last Post: Mar 22, 2014 5:35 PM Last Post By: Johnny P
Johnny P

Posts: 93
Registered: 05/28/08
Throttle Body Problem?
Posted: Jan 12, 2014 7:46 PM
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Hi all,

I had last installed a new Mass Air Flow Sensor and then cleaned the throttle body due to errors and the vehicle would not stay on when I would come to a stop. I performed the throttle body alignment procedure and got rid of my mass air flow error and the car ran great.
A week later I started getting these error codes. The car doesn't shut off but runs rough at times and then runs great again and the check engine light clears.

16504 Throttle Position Sensor (G69): Circuit Malfunction
P0120 - 35-10 - - - Intermittent

16487 Mass Air Flow Sensor (G70): System too High
P0103 - 35-10 - - - Intermittent

17535 Fuel Trim: Bank 1 (Mult): System too Rich
P1127 - 35-10 - -

16525 Oxygen (Lambda) Sensor B1 S2: Heating Circuit Malfunction
P0141 - 35-10 - - - Intermittent

I'm thinking the throttle body plate got misaligned any thoughts would be greatly appreciated!
'98 Jetta GLX VR6 AAA
tcovenant2000

Posts: 1,763
Registered: 12/09/03
Re: Throttle Body Problem?
Posted: Jan 13, 2014 6:51 PM   in response to: Johnny P in response to: Johnny P
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I'm thinking that all those intermittents are why the car runs crappy at times and well at other times. I would suggest you start by looking for a bad/crappy/corroded ground. I don't know where the grounds go, but suspect that's your answer. Most of these codes aren't related to the MAF. O2 heater circuit intermittent certainly isn't. Throttle Position Sensor isn't, either.
Thomas
Sky-Fi

Posts: 699
Registered: 04/19/07
Re: Throttle Body Problem?
Posted: Jan 26, 2014 4:38 PM   in response to: Johnny P in response to: Johnny P
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The important ground block is on the motor. I don't know where it is on a VR though. On a 2.0, it is behind the alternator right underneath the intake manifold on the front face of the block.

The O2 sensors ground themselves to the engine block, so does the ECU and the cluster. Dirty connections and heavily-corroded grounds will cause all kinds of issues. I know it's a bit of work, but go to the parts store and on the same aisle as tubes of RTV and stuff are, find a big tube of dielectric grease (I got one at Auto Zone for about $5 two years ago). After you find the ground block on the engine block and you wire brush all the corrosion away and grab some sand-paper and clean everything to shiny metal, slap the grease all over the ground block and plug things back into it and then put more ontop of all of it.

Then take every harness connection in the engine bay apart and check for corrosion, clean if needed, and then pack the connectors full of grease, too. The grease is not electrically conductive, so it won't short anything out, but it is goopy and keeps water and moisture out..which causes the corrosion in the first place. Corrosion plus water becomes conductive and can then short things out and cause electrical problems.

Since most of your codes refer to the O2 sensors, I would start with those though. Check/clean the connectors for them (down between the exhaust manifold and the firewall on the passenger side), and definitely look for the ground block that everything connects to. Fixing one problem may fix others in the process.
Johnny P

Posts: 93
Registered: 05/28/08
Re: Throttle Body Problem?
Posted: Jan 27, 2014 10:35 AM   in response to: Sky-Fi in response to: Sky-Fi
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Thanks guys great detail.
Man I got all sorts of issues now. After replacing the coolant pipe due to the broken off nipple going to the oil cooler, I developed a cylinder random misfire and a cylinder 1 misfire. Pressure testing revealed no leaks but shortly after, I developed a coolant leak around the oil cooler. That's the time the misfires happened. I sprayed soapy water to see if I had cracks in the coil pack and found nothing. I ohmed the spark plug wires and they fell within specks. I checked the plugs and they were dry. Spark plug one had some movement at the connector near the spark plug, so not sure if that's the problem. I unbolted the ECM and moved the wire connection around, but didn't notice a difference in performance.
Could this issue be related to my ground or the coolant spraying around the engine block?
Sky-Fi

Posts: 699
Registered: 04/19/07
Re: Throttle Body Problem?
Posted: Jan 27, 2014 1:19 PM   in response to: Johnny P in response to: Johnny P
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Misfires are typically because something got wet. I'm not too familiar with the VR6 setup, but I do know a place that is...if you can manage to ignore the few sarcastic people. Hop on over to VWVortex and you're likely to get more information there than here.
Johnny P

Posts: 93
Registered: 05/28/08
Re: Throttle Body Problem?
Posted: Jan 27, 2014 2:44 PM   in response to: Sky-Fi in response to: Sky-Fi
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I just re-read your reply earlier Sky-Fi about rechecking the connectors on my O2 sensors. I had replaced my sensors like 90K miles with some Bosch sensors made for Mustangs which were exactly the same except for the wiring. I kept the old connectors and just spliced the new sensors in. I got the info from someone here and they worked great. My splice probably heated up and is shorting now. I wrapped the splice in foil tape to protect from heat, but I bet that is what is shorting the wire to the chassis. I will check when I have some time on my hands. Now time to mosey over to vwvortex for my misfire issue.
Sky-Fi

Posts: 699
Registered: 04/19/07
Re: Throttle Body Problem?
Posted: Jan 27, 2014 2:50 PM   in response to: Johnny P in response to: Johnny P
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More importantly than the foil tape shorting out is since the splicing is on the exterior and exposed to the elements, butt-splicing is very much not recommended at all. It allows for a lot of corrosion to build up and that interferes with the signal. When doing that kind of splice, you should solder the wires together and insulate with heat-shrink tubing.. a tube on each of the 4 wires, and optionally, a larger tube on the bundle.
Johnny P

Posts: 93
Registered: 05/28/08
Re: Throttle Body Problem?
Posted: Jan 27, 2014 3:02 PM   in response to: Sky-Fi in response to: Sky-Fi
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I did do the heat shrink and soldering, but when I rechecked a few years back, the heat shrink got stuck to each other. All four wires with the heat shrink were stuck together due to the heat from the exhaust pipe. I thought the foil tape would deflect the heat. I think it's time to take the sensor and wiring off the car and check.
Sky-Fi

Posts: 699
Registered: 04/19/07
Re: Throttle Body Problem?
Posted: Jan 27, 2014 5:27 PM   in response to: Johnny P in response to: Johnny P
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Ah, okay. Good. So it was done right. For heat deflection, rather than wrapping foil tape on it, you need something that sits loosely over the wires, and backed by foil. I know the replacement O2s I got for mine a while back have a loose-fitting foil shield on them already. A lot of people don't realize that insulation from heat/cold relies on air gaps/pockets. Foil tape will just deflect some of the heat, but it doesn't do anything to insulate.
Johnny P

Posts: 93
Registered: 05/28/08
Re: Throttle Body Problem?
Posted: Mar 22, 2014 4:51 PM   in response to: Sky-Fi in response to: Sky-Fi
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Alright back to my issue, I have removed all connectors and air filter housing to find my issue with my intermittant codes. I did see a cluster of grounds under the battery tray and cleaned all and reconnected them. Now I have found a cracked oil breather hose which was spilling oil around the oxygen sensor connectors. Question is would a cracked breather hose valve cause my issues?
Sky-Fi

Posts: 699
Registered: 04/19/07
Re: Throttle Body Problem?
Posted: Mar 22, 2014 5:19 PM   in response to: Johnny P in response to: Johnny P
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as a matter of fact, the PCV breather system is post-MAF, and if the PCV breather system is not sealed up, then the air mixture that enters the engine is not what the MAF said it should be and that can cause running issues.

I cleaned my PCV system a while back and it made a noticeable difference in the way the engine sounded, revved, idled, and even helped mileage a bit.
Johnny P

Posts: 93
Registered: 05/28/08
Re: Throttle Body Problem?
Posted: Mar 22, 2014 5:35 PM   in response to: Sky-Fi in response to: Sky-Fi
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That valve with hose is $184 at the dealer. I'll search the other popular supply places first.
Thanks for the input Sky-Fi. I will clean all around there and purchase a new valve. The valve cracked on the side leading to the engine, so maybe the valve is not working properly either.

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