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I'm stumped on this one. I have a 1998 F-150 that intermittently transitions into a very fast idle. I notice it maybe once a day maybe while sitting at a red light.
I cleaned my IAC and put it back and it the idling seemed to stop for a week or two. Then it came back.
Then I completely replaced the IAC and no problems for a couple weeks....now the fast idling is back.
What's next? I suppose I could live with it as it may waste a little gas and spending $100 to fix a problem that will maybe cost me $20 in gas over the next five years isn't worth it.
I'm stumped on this one. I have a 1998 F-150 that intermittently transitions into a very fast idle. I notice it maybe once a day maybe while sitting at a red light.
I cleaned my IAC and put it back and it the idling seemed to stop for a week or two. Then it came back.
Then I completely replaced the IAC and no problems for a couple weeks....now the fast idling is back.
What's next? I suppose I could live with it as it may waste a little gas and spending $100 to fix a problem that will maybe cost me $20 in gas over the next five years isn't worth it.
Any check engine codes?
Also, what about the throttle position sensor?
Any check engine codes?
Also, what about the throttle position sensor?
I haven't checked the codes in a couple weeks. I have an OBD-II reader....I should have checked that before I posted....I'll do that after work here...
If this has an MAF, I just got done with a rough running problem on a 95 Cougar - prompted by Gimme3Steps I checked the MAF by unplugging it, tried to clean it, was so dirty that I ended up replacing it.
Reason I mention this is this system does not set a code, and the ECM is not "smart" enough to ignore a really dirty MAF (unless you unplug it).
Do check for codes though.
Don't forget to check for "old school" vacuum leaks as well.
It sounds like a vacuum leak. I had a similar problem in a 2003 Mercury. The fast idling was accompanied by a check engine light. I was in and out of the dealership and they couldn't figure out the problem. They kept charging me $80 for a diagnostic and to shut of the check engine light. Within a week or so, the check engine light was back on and I still had fast idling. They even charged me to clean out the fuel injectors and thought it was an engine cylinder misfire. That didn't fix the problem. It took until my car literally broke down until they realized it was a vacuum leak.
The intermittent fast idle will keep getting worse over time and one day your truck will stall out in the middle of the road. You will have to shut the engine off and re-start the car, then quickly press your foot on the gas to avoid stalling out again. I never did fix the vacuum leak and I traded the car in for practically nothing for a new vehicle rather than paying for the repair.
If this has an MAF, I just got done with a rough running problem on a 95 Cougar - prompted by Gimme3Steps I checked the MAF by unplugging it, tried to clean it, was so dirty that I ended up replacing it.
Reason I mention this is this system does not set a code, and the ECM is not "smart" enough to ignore a really dirty MAF (unless you unplug it).
Do check for codes though.
Don't forget to check for "old school" vacuum leaks as well.
It sounds like a vacuum leak. I had a similar problem in a 2003 Mercury. The fast idling was accompanied by a check engine light. I was in and out of the dealership and they couldn't figure out the problem. They kept charging me $80 for a diagnostic and to shut of the check engine light. Within a week or so, the check engine light was back on and I still had fast idling. They even charged me to clean out the fuel injectors and thought it was an engine cylinder misfire. That didn't fix the problem. It took until my car literally broke down until they realized it was a vacuum leak.
The intermittent fast idle will keep getting worse over time and one day your truck will stall out in the middle of the road. You will have to shut the engine off and re-start the car, then quickly press your foot on the gas to avoid stalling out again. I never did fix the vacuum leak and I traded the car in for practically nothing for a new vehicle rather than paying for the repair.
Is there an "easy" way to check for vacuum leak? I remember years ago all the AC air was diverted to the defrost vents due to a (now fixed) vacuum leak.
MAF = Mass Air Flow, the hot wire sensor that tells the ECM how much air your engine is pumping in so it can add the appropriate amount of fuel.
One way to hunt for a vacuum leak would be to hold one end of a length of tubing up to your ear and move the other end around in the engine bay with the engine idling. Be careful of rotating assembiles, belts, etc. This looks rediculous but works well. Usually a vacuum leak will be a vacuum hose cracked or pulled loose from the nipple it should be on.
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