U.S. CitiesCity-Data Forum Index
Go Back   City-Data Forum > General Forums > Automotive > Brand-specific forums > Ford and Lincoln
 [Register]
Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
View detailed profile (Advanced) or search
site with Google Custom Search

Search Forums  (Advanced)
 
Old 10-26-2012, 02:06 PM
 
Location: Las Flores, Orange County, CA
26,346 posts, read 80,765,097 times
Reputation: 17411

Advertisements

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.
Reply With Quote Quick reply to this message

 
Old 10-26-2012, 02:09 PM
 
Location: Maine
1,105 posts, read 1,432,245 times
Reputation: 1733
Quote:
Originally Posted by Charles View Post
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?
Reply With Quote Quick reply to this message
 
Old 10-26-2012, 02:18 PM
 
Location: Las Flores, Orange County, CA
26,346 posts, read 80,765,097 times
Reputation: 17411
Quote:
Originally Posted by CoastalMaineiac View Post
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...
Reply With Quote Quick reply to this message
 
Old 10-26-2012, 04:42 PM
 
3,186 posts, read 5,454,537 times
Reputation: 1818
I would replace the TPS and be sure that noting is sticking ...
Reply With Quote Quick reply to this message
 
Old 10-26-2012, 04:57 PM
 
Location: Eastern Washington
13,390 posts, read 42,724,996 times
Reputation: 11475
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.
Reply With Quote Quick reply to this message
 
Old 10-26-2012, 10:25 PM
 
3,854 posts, read 7,673,388 times
Reputation: 1853
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.
Reply With Quote Quick reply to this message
 
Old 10-27-2012, 05:29 PM
 
Location: Las Flores, Orange County, CA
26,346 posts, read 80,765,097 times
Reputation: 17411
Quote:
Originally Posted by CoastalMaineiac View Post
Any check engine codes?
Also, what about the throttle position sensor?

No engine codes.

Don't know how, where this is or how to check. Is it a pretty decent candidate for failure to cause high idle?
Reply With Quote Quick reply to this message
 
Old 10-27-2012, 05:31 PM
 
Location: Las Flores, Orange County, CA
26,346 posts, read 80,765,097 times
Reputation: 17411
Quote:
Originally Posted by M3 Mitch View Post
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.
What's a MAF?
Reply With Quote Quick reply to this message
 
Old 10-27-2012, 05:33 PM
 
Location: Las Flores, Orange County, CA
26,346 posts, read 80,765,097 times
Reputation: 17411
Quote:
Originally Posted by Nolefan34 View Post
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.
Reply With Quote Quick reply to this message
 
Old 10-29-2012, 02:39 PM
 
Location: Eastern Washington
13,390 posts, read 42,724,996 times
Reputation: 11475
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.
Reply With Quote Quick reply to this message
Please register to post and access all features of our very popular forum. It is free and quick. Over $68,000 in prizes has already been given out to active posters on our forum. Additional giveaways are planned.

Detailed information about all U.S. cities, counties, and zip codes on our site: City-data.com.


Reply
Please update this thread with any new information or opinions. This open thread is still read by thousands of people, so we encourage all additional points of view.

Quick Reply
Message:

Over $104,000 in prizes was already given out to active posters on our forum and additional giveaways are planned!

Go Back   City-Data Forum > General Forums > Automotive > Brand-specific forums > Ford and Lincoln
Follow City-Data.com founder on our Forum or

All times are GMT -6.

2005-2018, Advameg, Inc.

City-Data.com - Archive 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35 - Top