I was waiting in traffic today when the idle on my '93 ATX ran up to 3000 like the car was at wide open throttle. I got it towed home. Now anytime the the car is started in immediately revs to and tries to idle at 3000 rpm. I have replaced TPS. No change. Is the IAC the next likely cause?
High Idle
- Thread starter tlcsho
- Start date
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sperold
Last to Know
First, try getting some codes (stored and active).
The TPS was a good guess.
Try re-setting the idle after you disconnect the battery for awhile.
Test for a vacuum leak around your intake, as that is one of the few things that can happen as you drive around. But a long shot.
The TPS was a good guess.
Try re-setting the idle after you disconnect the battery for awhile.
Test for a vacuum leak around your intake, as that is one of the few things that can happen as you drive around. But a long shot.
Thanks for the response. I just retrieved the following KOEO codes listed below. The engine was cold when the codes were retrieved. I had removed and cleaned the IAC and replaced the TPS before retrieving these codes.
"O" codes: 116, 636, 121, 335, 116, 121, 335, 10
"C" codes: 337.
I am hesitant to idle the engine now, as on start it revs to 3000 stays there. The front motor mount is broken. When placed in drive the engine can be observed to jump up. So I guess I will need to deal with the engine mount first.
If the IAC failed and is stuck open might that cause the high, continuous idle?
Thanks
tlc
"O" codes: 116, 636, 121, 335, 116, 121, 335, 10
"C" codes: 337.
I am hesitant to idle the engine now, as on start it revs to 3000 stays there. The front motor mount is broken. When placed in drive the engine can be observed to jump up. So I guess I will need to deal with the engine mount first.
If the IAC failed and is stuck open might that cause the high, continuous idle?
Thanks
tlc
since the codes are displayed from lowest to highest, and there is no mixing of 2-digit and 3-digit codes, you have not counted them correctly. I suggest you post a video of the flashing cel so that we can count them for you so you know the correct way to do it.
the tps is not going to cause a high idle, so that was a bad guess.
your possibilities are 2: iac is sticking open badly, or a vacuum hose broke and you have a serious vacuum leak. I would start looking for the vacuum leak while I waited for the new iac to come in the mail.
the tps is not going to cause a high idle, so that was a bad guess.
your possibilities are 2: iac is sticking open badly, or a vacuum hose broke and you have a serious vacuum leak. I would start looking for the vacuum leak while I waited for the new iac to come in the mail.
rubydist,
Thanks for your reply. I will search for a vacuum leak. I use a digital code reader. I did not need to count them myself. I believe I wrote them down in the order I saw them display of the device. Anyhow, a new IAC will be ordered. If I run the engine with the iac unplugged will that suppress the idle speed?
Thanks
Thanks for your reply. I will search for a vacuum leak. I use a digital code reader. I did not need to count them myself. I believe I wrote them down in the order I saw them display of the device. Anyhow, a new IAC will be ordered. If I run the engine with the iac unplugged will that suppress the idle speed?
Thanks
You can troubleshoot the IAC by disconnecting it, to see if it is the problem. Obviously you won't want to leave it like that though.
luigisho
SHO Member
As ruby said above--The codes are usually in numerical order 116, 636, 121 are not in order & the number 10 is not a 3 digit code. Many OBDI code readers either display it wrong or they just flash an LED light and someone counts them wrong.
with the engine warm, if you unplug the iac the engine should just barely continue to run - about 500 rpm. however, that assumes that no one ever screwed with the throttle plate stop, which is not always a good assumption. if you unplug the iac and the high idle continues, that generally confirms the vacuum leak but it could possibly mean that the iac is completely stuck open (or I guess that throttle plate could possibly be sticking not all the way closed, but I have yet to see that). if you unplug the iac and the idle speed drops, that confirms the iac sticking.
if you unplug the iac and the high idle continues, I would whack the iac sharply to see if it is sticking. then I would hunt long and hard for a vacuum leak.
if you unplug the iac and the high idle continues, I would whack the iac sharply to see if it is sticking. then I would hunt long and hard for a vacuum leak.
SOLVED. A proper idle has been reestablished. Replacing the IAC or TPS resulted in no change. A search for a vacuum leak was futile. However, on inspection of the throttle I determined that the cable that connects the throttle to the cruise control was putting tension on the throttle spring, preventing the throttle plate from returning to its rest position - thus allowing a consistent, increased supply of air to be drawn in - resulting in a high idle. The cruise functions in this car do not work, so I simply disconnected that cruise cable from the throttle. Now the engine purrs along at a civilized 800 rpm in park, an returns to the same point when rolling to a stop.
Thanks again to all who responded. Your knowledge of these cars is very helpful and encouraging.
Thanks again to all who responded. Your knowledge of these cars is very helpful and encouraging.
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