Idle Surge / Rough Idle - Vacuum leak?

[Theo90TSIAWD]

Just to make sure my understanding of this is correct, this is idle surge right?:

<embed width="448" height="361" type="application/x-shockwave-flash" wmode="transparent" src="http://i268.photobucket.com/player.swf?file=http://vid268.photobucket.com/albums/jj20/TheoDAtHome/0719091239.flv">

From searching the forums and from the little bit of experience I have with it, I have three steps I'm going to take as my first attempt to try finding my leak.

1.) Test my IAC

2.) Test for a vacuum leak

3.) Boost test

They are sorted from what is in my opinion easiest to hardest. Any thought, suggestions, or opinions are welcome. If you turn up your speakers you can here the idle, but just watching the video obviously shows what it's doing.

 

[steve]

Just to make sure my understanding of this is correct, this is idle surge right?:

From searching the forums and from the little bit of experience I have with it, I have three steps I'm going to take as my first attempt to try finding my leak.

1.) Test my IAC

2.) Test for a vacuum leak

3.) Boost test

They are sorted from what is in my opinion easiest to hardest. Any thought, suggestions, or opinions are welcome. If you turn up your speakers you can here the idle, but just watching the video obviously shows what it's doing.

Yes that is idle surge.

Why is the oil pressure reading nothing, the oil pressure warning light active and your taking videos of the surging?
.
Both the ISC and ECU have to be checked, they are part of a system.

Anything that allows air to reach the intake manifold can cause surging. Make sure you throttle cable has some slack when the throttle is closed, that you have a good BISS o-ring, that your rocker cover breather is connected to the intake tube.

The pressure test (boost leak test) should find the vacuum leaks too.

 

[decathect]

steve makes a good point... get that oil thing fixed.

Also, test your ISC and not your IAC:

DSM simple test page

Do the boost leak test first though. That usually exposes lots of leaks to fix, and makes further diagnosis much easier. As steve said, skip the vacuum test, boost leak test will cover both.

 

[Theo90TSIAWD]

Yes that is idle surge.

Why is the oil pressure reading nothing, the oil pressure warning light active and your taking videos of the surging?
.
Both the ISC and ECU have to be checked, they are part of a system.

Anything that allows air to reach the intake manifold can cause surging. Make sure you throttle cable has some slack when the throttle is closed, that you have a good BISS o-ring, that your rocker cover breather is connected to the intake tube.

The pressure test (boost leak test) should find the vacuum leaks too.

The wire that hooks up to my dummy light doesn't stay connected. One of my leaks that I have fixed was dripping power steering fluid all over the alternator, oil gauge sensor, and the dummy light and has created some problems.

I need to buy some new wire and connectors and the light will go away.

What does "ISC" stand for? I will check out the rest of your suggestions, thank you.

 

[Theo90TSIAWD]

steve makes a good point... get that oil thing fixed.

Also, test your ISC and not your IAC:

DSM simple test page

Do the boost leak test first though. That usually exposes lots of leaks to fix, and makes further diagnosis much easier. As steve said, skip the vacuum test, boost leak test will cover both.

That's a great link. Looks like it's just an easy to read summary of the test process' found in the service manual, very nice to have, thank you.

The oil thing is adressed in the other post I just made. And I'll do the electrical tests tonight and the boost leak test tomorrow after I make sure I have everything I need.

Thanks!

 

[decathect]

No problem. I love that page, i've tested almost all of the things specified, and a few of them have been bad. Its saved me headaches!

 

[Theo90TSIAWD]

So I busted out the multimeter and was ready to go to town on the electronic tests and I ran into some problems. I'm having issues figuring out what is what haha. Yes, it's sad I know. I'm hoping you can help me label a few things.


In this picture, this part circled in yellow is the IAC right, not the ISC?

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In this picture below, the blue plug goes to my CAS

I have no idea what the purple plug goes to

The green one splits off in two directions, half of the coil goes to the red plug and I think the other half is plugged into what I'm assuming is the AIC in the picture above.

The red plug, connected to the ECM I assume and I'm not sure what else?

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Can any one help me make some sense of this. The goal was to test my ISC and TPS, but I have no idea what to test. Whet I am calling a plug a certain color, I am talking about the color used to circle it, just in case anyone didn't catch on to that. I looked at the repair manual for this one too, but apparently I need the 1st grade version.

Thanks to anyone that can help out.

 

[steve]

In this picture, this part circled in yellow is the IAC right, not the ISC?
In this picture below, the blue plug goes to my CAS
I have no idea what the purple plug goes to
The green one splits off in two directions, half of the coil goes to the red plug and I think the other half is plugged into what I'm assuming is the AIC in the picture above.
The red plug, connected to the ECM I assume and I'm not sure what else?

Best I can tell.

Yellow - Throttle Position Sensor (TPS)
Blue - Crank Angle Sensor (CAS)
Purple - Injector Resistor pack
Green - Throttle Position Sensor (TPS)
Red - Idle Speed Control Actuator (ISC)
Light Blue - Idle Position Switch (IPS)

 

[Theo90TSIAWD]

I assumed the red one went to the ISC as well and I assumed that would be the plug used to test it, but it's only a 4 prong and supposedly it's supposed to be a 6 prong.

 

[steve]

I don't have a 90 so I'll need better pictures showing the wire colors and where then come from and go.

Or you'll need someone who does own a 90 to pipe up.

 

[Theo90TSIAWD]

These were taken with a cell phone and flashlight. I will get in with an actual camera and get some better pics this weekend and post them up.

 

[talon_tempers]

First post. I have been having the same problem with my 1992 tsi. Purchased her about a month ago and i noticed as i was pulling up into the previous owners driveway he was adjusting the biss with the engine running? I figured this was my problem the car would die at idle and surge from 2k to 800 when cold. I had every Boost/Vacuum leak imaginable. Injector insulators, intercooler couplers, throttle body gaskets, turbo gaskets, 2 BOV's? eliminated one closer to intercooler.. As i ran the most recent boost leak test earlier today i noticed i also have a bad biss O ring and possibly bad intake manifold gasket. This idle surge thing seems to be very notorious and the culprit could be just about anything.