Idleing problems

[KeithStang]

I have a 94 5.0 w/162,000 miles. My mods are in the sig. My idle likes to bounce up and down. If I let it do it's thing it will eventually die. I don't own a code reader nor have I had it checked for any codes thrown. I've never changed a sensor either. What are the common gremlins that make this happen? Thanks for the info.

 

[Silver85TC]

Could be alot of things.

First thing would be to check the codes. Do a search to find the method....its very easy to do (jumper the test connectors with a paper clip...count check engine light flashes).

Second.....a COMPLETE tuneup. New....;
- plugs
- cap
- rotor
- plugwires
- fuel filter
- clean MAF meter with electronic cleaner
- clean throttle body and idle air bypass valve with intake cleaner
- check timing
- check all vacuum hoses for leaks
- check fuel pressure
You can do each of these items, one at a time to see if it makes a difference, but if you havn't done a tuneup on the car before, all of the above should be completed (you'll be amazed at the difference).

Third, if you're still having idle problems and have completed the tuneup and resolved any codes that the computer throws, you may have to look at the sensor's. A sensor can be bad and still not cause a check engine light.
The sensors that WILL ABSOLUTELY cause an idle problem if they are bad are the Air Charge Temp sensor (ACT) and the Engine Coolant Temp (ECT) sensor.

Fourth, if you're still having idle problems, you might have to adjust the idle set screw.......I would definately complete all of the above items before I did this though. (didn't have to do this on my car)

Assuming that you're car just has normally wear and tear (no major mechanical problems), completing the above steps should settle your idle down. I've completed all of the above steps on my 95 GT over the past year, and my car idles rock steady at 700 RPM and feels real strong for a stocker when driving. (It idled/drove like $h!t when I first bought it last summer)

Hope that helps.

 

[95stocker]

Everything that silver85tc is right, but I just want to add something that I did that fixed my idle somewhat.

It didn't totally fix the surging problem, but it fixed most of my problem, but I replaced the PCV valve. I get better gas mileage also.

 

[mo_dingo]

Run the codes. See what you get. Here

Secondly, hook up a vacuum gauge. See what it reads. Write down how much vacuum you have. Also note if the vacuum changes at all. If it bounces up and down, let us know.
Scott

 

[xr8d302]

yeah, if that MAF sensor get's any oil on it from the filter you're using, it'll cause a common idle surge issue, but that still doesn't explain the car dying.

 

[KeithStang]

Thank you guys very much. I'll get to most of it this weekend and let you know how it went. Thanks for the time you took to type in all the info too.
Keith

 

[bjmellon]

as MO touched on, check for a vacuum leak. This can be done by: listening for it, or spraying carb-cleaner (2+2) on spots that can be susceptible.. like around the lower intake mounting point, upper- same as lower, around tb, anywhere vacuum can leak.... Don't forget internal leaks, this can be checked by pulling the pcv and spraying 2+2 in the oil fill cap. If you have a leak somewhere, the idle will jump up when you spray on the spot of the leak, you may also notice a white smoke out of the tail pipes if severe enough. I'd say vacuum leaks are the #1 cause of sudden idle-hunting
Hope this helps!!

 

[will4193]

all these are good ideas, but with high miles I would try cleaning the throttle body!!! Just take some carb cleaner on a rag and clean around where the plate hit the sides of the throttle body. If you look up into the body and open the throttle I'm sure you'll see the black crap. Just an idea.

 

[BlackVert]

my idling problem turned out to be that the idle air control valve was sticking closed. is is a simple thing to replace and it costs about $45 at autozone.