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Showing results for tags 'pcm'.
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Good Day! I hope you're enjoying a pleasant one. It's been a while since I've visited this site. I have a '90 Lumina Coupe, and a 91 Sunbird Convertible, both with the 3.1 V6 (both now on the project pending list). I thought I saw a couple of articles here, from long ago, that might come in handy now. One was a wiring diagram to install an under dash switch to bypass the computer for turning on the cooling fan manually. Another article gave instructions for resetting the computer after disconnecting the battery. I looked in the FAQ section but had no luck. Are they here somewhere, moved, hidden? Does anybody know what I'm talking about and can maybe point me in the right direction? Respectfully, John V. Brennan
The buick has been doing some interesting things when it is wet outside. I noticed this last November, but the car sat for a good chunk of winter, and the problem has not self resolved . Sorry for the long post, but here it goes: With the brakes not applied, it seems to surge. This happens when the car is cold and has sat overnight in high humidity. Understandably, the surge is even worse when the idle is high right after a cold start (it is enough to shift into second). When the brakes are applied, it behaves normally. My first thought was the brake booster is leaking a little vacuum when not applied. I suspected that that is not the issue because there was no air sound and it was very intermittent. I have a switch that turns off the tcc by grounding the brake switch input at the pcm, so I used that to test my suspicions, and sure enough, the brake application itself is not the issue, it is just the pcm thinking the brakes are on that makes it behave. Like I said, the car got to sit out the winter months, so... fast forward to today: I was finally able to catch it in the act on tunerpro. I tried multiple times before but sometimes it would do it only for a few braking cycles, so by the time the laptop was on, it was behaving, or at least so it seemed . So here is the link to the xdls from my trip to work today: https://drive.google.com/folderview?id=0B6AKqXKswy6VMVRkQzljNUZCMG8&usp=sharing Two files, one on my street just showing the behavior at idle only, the other is the rest of my 22 mile trip. The tps signal is what I can see causing the surge. This tps is about a year and a half old. I replaced the connector at that time too. The fact that the brake switch signal changes the tps makes me think that the issue is not in the tps itself, but rather at the pcm side. The closed tps voltage is 0.57. It jumps up to 0.63 or 0.61, sometimes alternating, as soon as the brake is not applied. This happens with either the brakes actually being used or me using the switch to ground the brake switch signal. Two things I noticed: -The behavior slowly got better as the trip went on (towards the end the voltage only jumped to 0.59, and not at all at the very end). -The pcm tried to learn the 0.61 as the 0% throttle position (but pretty sure engine still surged a little), but I would burst its bubble every time I hit the brakes and dropped the voltage back to 0.57. I am not super well versed in tunerpro and calibration, so I could be missing something important. I am suspecting condensation in the pcm or the wiring next to it, because the engine heat could be burning it off. Is that an idea to chase? I have thought about making it waterproof somehow to try and eliminate that.