# 99 VW Golf MK4 2.0L 8V - Running Too Rich/No Power



## mtlgolf4 (Nov 25, 2013)

I have a 1999.5 MK4 Golf with the 2.0L 8v AEG engine. This is my winter beater car that I drive about 20 mins everyday to and from work. About a month ago the check engine started intermittently coming on during my commutes. I would drive in the morning with it on and when I drove home in the evening it wouldn't show up, all the while the engine was running fine, nice a peppy. I kept a code scanner in the toolbox of my trunk and every time I checked it. It was a *P0172 - Engine Running too Rich (BANK1)*. I did a quick check of the MAF and TB which were cleaned in the fall (but I cleaned them again), The air filter is new, and I looked to see if there were any leaking vacuum lines...none that I saw. I didn't have time to look at when it this problem came up... time/bad winter weather. I was planning on dealing with it this weekend when...

Today however on the way home from work the car was running terribly. I had my foot to the floor and it was barely going anywhere, and the check engine light was flashing a cylinder 4 misfire. I managed to get it home, but it idles badly and when i give it a good rev it stalls now. One day its running alight, today can barely keep it going. I made a YT video.


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## Anony00GT (Mar 6, 2002)

What are your fuel trim numbers? Did you perform throttle ADP with VCDS after cleaning the throttle body? FWIW, it's nearly impossible to actually clean a MAF element. If the MAF is bad, it must be replaced (and disconnecting it is not a good diagnostic procedure).

Check secondary ignition components as well.


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## mtlgolf4 (Nov 25, 2013)

This doesn't have drive by wire. The TB is cable operated so I don't think I need to perform an alignment with VCDS.


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## dfpimp (Sep 1, 2007)

mtlgolf4 said:


> This doesn't have drive by wire. The TB is cable operated so I don't think I need to perform an alignment with VCDS.


Even drive by cable throttle bodies should be aligned with VCDS as they still use an electrical motor/servo to adjust the idle speed.


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## mtlgolf4 (Nov 25, 2013)

True, but several people on here and my indie tech said that simply pulling the battery will reset it, while the complete drive by wire will not. This has always worked.


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## Anony00GT (Mar 6, 2002)

mtlgolf4 said:


> True, but several people on here and my indie tech said that simply pulling the battery will reset it, while the complete drive by wire will not. This has always worked.


The posts you're reading on here, and your indy tech, are both wrong. VCDS is the only way to properly do the throttle ADP. And yes cable throttles need it done when they're disconnected and/or service is performed on them. Sometimes they will re-learn on their own, but not every time, and not always without throwing a fault code.

What are your fuel trim numbers (MB 032 in VCDS, or LTFT and STFT with generic OBDII)? Get those numbers before clearing the code(s).


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## mtlgolf4 (Nov 25, 2013)

all right, so its been awhile but I finally got around to taking a look at the car. Funny thing is I pulled the battery cables awhile it sat and put it on a charger since it was going to be really cold the whole week. Hooked it up again today and the car runs great...starts fine,I can rev it and it doesn't stall, and there are no check engine codes???

I decided to check the plugs anyway. So I pulled all of them and this is what they look like:










Look pretty burnt, they didn't have any gas or oil residue on them. Going to change anyway. I'm still waiting to hear back from a friend who has VCDS to try and perform an alignment on the TB.


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## Anony00GT (Mar 6, 2002)

Also get fuel trim numbers. They should be measuring block 032 in VCDS.


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## mtlgolf4 (Nov 25, 2013)

Do you happen to know if that's available in the shareware version?


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## roadsterred (Feb 25, 2010)

Have you checked or replaced your Coolant Temperature Sensor? It may have failed.


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## Anony00GT (Mar 6, 2002)

mtlgolf4 said:


> Do you happen to know if that's available in the shareware version?


I think it is. But I highly recommend registering it and getting the full version anyway.


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## mtlgolf4 (Nov 25, 2013)

So changed my plugs and replaced the vacuum line between the manifold and fuel pressure regulator. Thought it was fixed but...Yup too good to be true. After a few days my CEL came back with the same P1702 Bank1 running rich code. Engine still has a good rev and power, but the exhaust smells heavy again. So its only a matter of time before these plugs get burned. Going to go back to vacuum line checking. Got a hold of my buddies VCDS, but its the shareware version with the chinese knock off plugs that works occasionally. Haven't been able to get it to function to get a fuel trim status.


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## Mr.Blonde42 (Sep 18, 2014)

roadsterred said:


> Have you checked or replaced your Coolant Temperature Sensor? It may have failed.


This was my issue a while ago. It wouldn't start, flooded randomly, cel would come on randomly, and my cabin would STINK of gas. My codes came back for CTS changed that and fixed it. It's only a eleven dollar part. It couldn't hurt to try it.


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## mtlgolf4 (Nov 25, 2013)

CTS?


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## evanj (Jun 1, 2014)

Coolant Temp Sensor


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