Fastscirocco

Gentz,

Previously the car's idle would "pulse" up and down, I cleaned the
ISV with carb cleaner and it idled better but not "right".

Apparently I have a defective ISV, wondering how it works.
With the ISV's wires plugged in the car won't idle and dies when
the throttle isn't pressed. Unplug the ISV's wire and the car idles but
I get a check engine light.

Nothing else was unplugged on the engine, I know some people have
plugged a different cable in to the ISV and the car ran bad, this
isn't the case.

Is the ISV servicable or does it need to be replaced?

UrS4boy

throttle closed (your foot off the pedal), the computer controls the air flow around the throttle plate by opening or closing the ISV opening via the stepper motor. For example, at idle with the air con on, when the compressor kicks in, the ECU senses the drop in RPMs and then tries to compensate by opening the ISV a bit. When the air con compressor goes off, the ECU closes the ISV, trying to maintain a constant idle speed eg. 800 RPM.

UrS4boy

<center><img src="http://pictureposter.audiworld.com/15624/n71idlespeedstabilizer.jpg"></center><p>

UrS4boy

<center><img src="http://pictureposter.audiworld.com/15624/n71idlespeedstabilizer2.jpg"></center><p>
It's basically a valve that is connected to a motor that is controlled by the ECU. With the throttle closed (your foot off the pedal), the computer controls the air flow around the throttle plate by opening or closing the ISV opening via the stepper motor. For example, at idle with the air conditioning on, when the compressor kicks in, the ECU senses the drop in RPMs and then tries to compensate by opening the ISV a bit. When the air con compressor goes off, the ECU closes the ISV, trying to maintain a constant idle speed eg. 800 RPM.

Audi Part number is 034 133 455 B
Bosch PN is 0 280 140 512

Sometimes they get dirty and need to be cleaned. Carb cleaner can work as can isopropyl alcohol washed through the air passage. Dry before using.

NOTE: The intake air temp sensor and the ISV connectors are the same shape and, therefore, you need to make sure the correct connector goes to the correct device if you have both off at the same time for some reason.

esj

Driving home this week the check engine light said hello. Luckly, I was just about home. I safely made it there and after a couple of hours I tried to restart but no luck. It appeared to be not receiving any fuel. I tired a few more times and soon enough it started again, sounded and ran fine, as well as the check engine light was now off. The fault code was 2231, which led me here and your ISV diagram. I will clean it up and see how it looks tomorrow. The other component that appears to be associated with this fault code is the MAF.

As always Dave - Thanks for the info. You have helped me many times over the years.

UrS4boy

You probably have another issue. An ISV typically doesn't result in a re-start issue. You are probably not done with this. Don't be surprized if your fuel pump dies.

For more info about the ISV, MAF and G6 Fuel Pump, click on the link to the diagram below and then on the appropriate label (they're all hot links to more info):

http://members.shaw.ca/speedtek/UrS%...ice%20Map.html

Good luck.

esj

It was a simple job to remove the ISV, and the reading was 8.5 ohms. It was dirty so I cleaned it up with some carb cleaner and hooked it up to a 12V source and the mechanism in the value seemed to work fine. Cleaned, dry, re-attached and ready for a test drive. I drove it a little bit yesterday and the check engine light turned ON again. Before I turned off the engine, I unplugged the wire harness from the ISV. I notice the car idled a bit rough with the connection off. When I reconnected the wire harness, the idle quickly returned to normal and the check engine light was OFF.

When this began, my first assumption with the fuel was not flowing. It felt/sounded like the engine was just waiting for fuel, like the tank was empty.

Since the error code "2231" pointed me to the ISV and MAF I figured I would start me search there. ISV appears to be working fine. Do you think the faulty MAF could be the cause of an intermittent fuel problem or should I focus on the fuel pump?

Any insight would be appreciated. Thanks again.

UrS4boy

•2231 (Blink Fault Code), 00533 VAG1551/2 Fault Code Number
Idle Speed Control Valve (N71)
Idle speed adaptation maximum limit exceeded or Minimum adaptation limit not reached
Sticky or binding ISV, Mass Air Flow Meter (G70) offset, additional air introduced between G70 and N71
Symptom: Idle speed too low, or too high, Add air leak.

You might want to do a boost leak test. https://www.audiworld.com/forums/sho...AAN+boost+leak

As for the G6 Fuel pump, go back to that Engine Bay Device diagram with its hot links and click on the G6 label re: fuel pump testing, etc.

esj

Here is the latest - I rechecked the codes last night and I'm now seeing this flashing code. I'm seeing the check engine light in my sleep :-)
Taking my car to an Audi Expert today for a fuel pressure test.

2413 (Blink Fault Code), 00561 VAG1551/2 Fault Code Number
Mixture Adjustment,
Adaptation limit exceeded, Adaptation limit not reached, Leakage in exhaust system before 3 Way catalytic converters, Incorrect signal for Mass Air Flow Sensor, Spark plugs, ignition coil(s), or Ignition Coil Power output stage malfunctioning
Symptom: Rich mixture, increased fuel consumption

GoHeels

I actually got the same 2413 code this spring as I left town on a trip. Went back to the house and everything "seemed" okay, so I left town an hour later. When I got to Charleston the car wouldn't start. Ended up being the Cam Position Sensor, which thankfully was a relatively easy fix.