high idle rpm >13mph!

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

 

[curtis]

When you find out let me know because Ive had a surging idle problem for about a year 900 to 1800 idles sometimes and sometimes it doesn't. Ive checked timing, change four different idle motors, played with the idle screw, played with the closed loop idle sensor, TPS, pulled screens out of the meter, upgraded to a holley fuel rail and aeromotive regulator played with fuel pressure, vented the HKS blow off back in ,etc...Nothing seems to work I heard theres some kind of wheel sensor/vehicle speed sensor but I'm not sure where it is or I would have changed it.

 

The speed sensor is in the speedometer. KC is gonna send me one, so I can play with it and document (hopefully) how to replace it with a cheap Radio Shack reed switch.
But, I don't think that is my problem, because I logged memory location C6 using the MMcD logger, and it appears to be working OK. It starts out at 226 when you aren't moving, and QUICKLY drops, until its only like 7 or 8 at 45 mph.
Plus, the car still does idle up about 200 rpm whenever its moving, which is the way its supposed to when the speed sensor is working right.
Thanks, and keep the ideas coming.

 

[ken inn]

yo, jeff, i got a spare instrument cluster that i KNOW works. it is in my car right now. i can send it if you need it. i also got a spare ecu that i KNOW works. maybe all the ecu switching has got your car confused, it might think it's back up north. you know, like jet lag.

 

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.

 

I just picked up my GVR4 yesterday and I have the same idling problem. My ABS light is constantly on, but the guy I bought it from who just opened his shop and is a very well known DSM mechanic in the area said he unplugged the ABS fuse cause the ABS was kicking in when it shouldn't have.

I dunno what to do about that problem, but now that you related it back to the 20amp fuse, I might have an idea. I still have the fuse, but where exactly did you pull it from?..the kickplate or underhood? Like I said, I just got the car and am very unfamiliar w/ it right now.

 

[Hertz]

Under the hood, near the battery.

 

Thanks alot...I'll give that one a shot tomorrow morning. The guy I bought it from said he pulled the fuse because the ABS motor was kicking in even when it shouldn't be, how would I go about fixing that problem? Is there another ABS fuse I could pull or disconnect it from the motor in the trunk?

Again, I apologize about the newbie questions...I'm just trying to get everything all squared away on the car. Just a couple other things to try to take care of as well.

 

[Doc_Seuss]

ok well it seems like you guys are responding to this topic so i will throw out my question....

ok usually my idle is about 850-1100 depending.. well i put my a/c on and idle drops to 650-800. enough to make my car shake and not normal. I have played with my BISS and dont really have any other ideas. I have also changed my ISC motor with still no avail, just looking for some ideas...

thanks alot
dave

 

The ABS computer could have been faulty. I had the same problem a few years ago. Unpluged the ABS computer and it went away. It's located behind the left trunk liner. You can access it through the jack opening.

 

[Turbo4door1]

Dave (Doc_seuss) -- I was having very similar problems to you, and I did a couple things all at once that fixed it. I'm not sure exactly which one fixed it, but one (or all) of them did. I replaced the ISC unit with one I got from Gabor, replaced the throttle body shaft seals (which were basically not there anymore), re-adjusted the Throttle Position Sensor, and reset the base idle speed (properly, by grounding both of the pins that need to be). My ISC was testing good, but I replaced it anyway just to eliminate that as a problem. Just throwing some ideas out there, hope one of them might help.

 

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.