high idle rpm >13mph!
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keydiver Unregistered
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posted 06/07/03 06:33 PM
OK guys, its your turn to give me some ideas: Between all the things I've done/had problems with lately, I don't know what could have caused this, but whenever the car is >13 mph the ISC sets itself to a very high setting, like 120 or 130! Usually, the ISC does go up to about 60 while cruising, if I remember correctly, but now it stays at 130 until I slow down to <13 mph. I don't know if its related at all, but I did have the brake problem last week, I had the A/C problem that turned out to be a bad sensor wire, and of course I've been testing several people's flaky ECU's lately. I've logged all the sensors, and everything looks OK!! I even looked at address C6 in the ECU which is the speed sensor, and it seems to be behaving the same as I remember it before. Has anyone heard of such a weird problem? What else could cause the ECU to want to crank the ISC up so high???
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keydiver Unregistered
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posted 07/08/03 09:06 PM
OK guys, for the records, I finally figured this one out: In case you ever have the weird symptoms of high idle until your car drops below 13 mph, check the 20 amp ABS fusable link. I had robbed it to replace my main ECU power fuse I blew while working on someone's ECU. Once I plugged a 20 amp fuse back in, the problem vanished! I thought it was ABS related, because I had noticed before, when the ABS was working, that everytime the ABS kicked in my rpm's went up. Curtis, here's something else for you to try, that will tell you if it is ECU/ISC related: the next time it is idling fine, put the A/C on to raise the rpm's slightly, and then unplug the ISC connector. Try driving the car for a while with the ISC locked in that permanent position, and see if it stays low. It will be a hassle when you do cold starts, it may be too low, but it will tell you if the ECU or ISC is raising the idle. I did this to troubleshoot my problem, and it went away. Also, when I was testing an ECU that wasn't made to be ABS aware, it went away too, which lead me back to the ABS fuse.
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keydiver Unregistered
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posted 07/09/03 10:49 AM
quote: Originally posted by Doc_Seuss: ok usually my idle is about 850-1100 depending.. well i put my a/c on and idle drops to 650-800. dave
Dave, Do you have a logger? It would be interesting to see what the ECU *thinks* the ISC is doing. I find that about 50% of the ECU's I get for repair do NOT have a funtional ISC, usually due to the cap acid eating an ISC trace right below the 47 uF capacitor. If you can log it, and the ECU *thinks* the ISC is at 60 or more all the time, you probably need to get the ECU fixed. If you have any electronic experience, I can tell you how to ohm out the traces on the board by memory, I test EVERY ECU that I get, and it is VERY common.
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