Please help a non tech guy.
Please help a non tech guy. When I am on the brake about to come to a complete stop from a highway speed it feels like my transmission or converter is re-engaging and I get a weird slight forward motion. It is going too slow at this point for me to think it is automatically downshifting into first gear. No noise or banging and it is not surging, it feels like someone taps the car from behind. It is an A4 w/ A 3200 Circle D stall that shifts firm & perfect.
Here is why I am guessing it is an electronic issue. I just installed a new drive-shaft, posi unit and rear axles for a different vibrating issue, this problem was there both before & after. The car was dyno tuned by a well known competent tuner and it runs great, I sent the pcm back to him just to raise the lock up from 42-48 mph. I believe this is when I first remember noticing the issue, I can't imagine one is related to the other? I am thinking and or hoping there is a sensor like the tcc, tps, iac or afu sensor that just needs to be reset but I don't know which and guessing is not a great idea. Thanks for any help, I hope I was specific enough.
Here is why I am guessing it is an electronic issue. I just installed a new drive-shaft, posi unit and rear axles for a different vibrating issue, this problem was there both before & after. The car was dyno tuned by a well known competent tuner and it runs great, I sent the pcm back to him just to raise the lock up from 42-48 mph. I believe this is when I first remember noticing the issue, I can't imagine one is related to the other? I am thinking and or hoping there is a sensor like the tcc, tps, iac or afu sensor that just needs to be reset but I don't know which and guessing is not a great idea. Thanks for any help, I hope I was specific enough.
When you say converter is engaging do you mean the lockup? With that converter If it was locking up coming to a stop it would be quite violent, and likely stall the engine, I don't think that's whats happening. It sure sounds like the trans downshifting from 4th to 1st. Does it not feel the same if you go from N to D? At what RPM is this happening? It's possible your rolling idle speed could be significantly higher than the stopped idle speed and downshifting from 4th to 1st is causing a higher 1st gear engagement.
First, thank you for taking the time to answer me. It is not violent so I can rule out the converter. Maybe on the second time around my tuner changed the rolling idle speed as you call it? I will have to look the next time I drive the car what RPM this is happening at but it sounds like what you're describing. Do I need my tuner or hptuners to fix this if that's what it is?
Yeah there are 2 fields for that in hp tuners. The rpm settings for rolling and stopped, and rolling and stop speeds. Usually rolling idle is higher than stopped idle, but you can increase the speed at which it transitions to stopped idle and I think factory is like 4-5mph but you can increase to around 8-10 to factor in a bit of lag time. But yes it'll have to modified with hp tuners or efi live.
It feels like it's around four or five miles per hour but I will have the car out Tuesday. I will notice what mile per hour and what RPM it is doing it at and reach back out to you if it's okay? Thank you very much.
