Re: Who wanted to know- raising A3 idle?

That was my post. I'm down to the computer, and the big problem I'm having is that I've tried another computer (wrong code...AA instead of AH), so I can't get my mind off the fact that the test may be flawed due to the fact that I didn't try a computer with the same code. Any questions as to what I've done can be answered by the post I made last night:

After the car warms up, putting it in gear makes the rpms drop to 680 and stay there! Same with air conditioning. You turn on the air and the rpms drop and don't come back up. The thing is, when it's cold the Idle air control works exactly as it should. Only after the water temp passes 72c do the rpms turn to crud. I've run every test I can find and have even come down to that humiliating ritual of swapping parts. The only info I can find in print on this problem is on Alldata. The trans troubleshooting section says if you have this condition that the ECM is bad. I swapped computers with my other 95 Jetta and it displayed the same exact problem. The only thing is, the computer didn't have the exact same code. It was an AA and the one with the problem is an AH. Could it be possible that it's still the computer and I need to get one with the same code? I find it hard to believe that it would have the same problem, PLUS I put the computer from the trouble car into the donor car and it ran normally. Any help is appreciated.

Tim

This info is for 96 and up A3's so it may not work for your car. With ross-tech enter:

There should be a number there that is set to 128(default). You can change this from 124 to 132 to lower or raise the idle Each number you change by one will raise or lower the idle about 10rpm. Like I said this may not be for your car...

Besides the model year, is this information also for manuals? I was wondering if this was more of an automagic problem. And, does this raise the idle only during AC operation if manual? More of a slush box idle adjust methinks...

OK, well this morning I decided to pull the coolant temp sensor and the intake sensor and see how that went. After it was definitely warm, the rpm's did not drop with the air or the drive selection. As soon as I plug EITHER sensor in, the idle drops. I looked to see what these two sensors have in common and they share the (sensor ground) in the MFI harness. But damned if I can find the point of the ground. Any help with that would be great.

Tim

Here's a thought, bypass the actual ground with trailer light splicers, you know the 2 wires go into the plastic, one goes through and one doesn't. Then you use pliers to clamp down on the metal to splice into the wire. Run one wire to ground and splice through it for both wires.

Yeah, that's the main ground bus, but I'm talking about the sensor ground that is somewhere in the main harness. It could be anywhere as far as I know. In the wiring diagrams, it doesn't give an exact location (i.e. main bus), it just says "ground connection in MFI wiring harness".

Tim

Good idea but don't use the splicers, to much a chance for resistance and corrosion in time.

If I understand the problem correctly, why not simply tap into the sensor wire at the sensor and run a new ground wire to the closest real grounding source?

Bill