Chips and wires and sensors oh my?!?

[Thelgord]

I am fairly new to this site so I hope I am asking this in the correct section.

I have 91 XLT, and after it runs from a cold start for around 2-3 mins. the idle speed drops to around 650RPM. This has the added effect of making the lights (all of them) dim and brighten in time with the engine. (can give you head ache) At night, while sitting at dead stop (such as a lighted intersection) the effect is so noticeable that my head lights appear to blinking rapidly.

I found a link on hear about the air flow sensor and how to clean it. This has helped a little, (it did idle closer 500RPM before the cleaning), but the problem persists. I have tested my altenator at a two shops and they say its working fine. Both seem to think it's a battery getting ready to fail or a grounding problem. I can chase a wireing problem if that is really what is going on, but I would rather not if this would be a waist of time.

Any ideas would be most welcome.

 

[Vanquish502]

Just get a screwdriver and turn the idle up...lol

 

[Thelgord]

Ummmmm .. no.

I prefer to make my repairs the correct way, and so I did. If any one else has this problem its an easy fix. All I had to do was change the negative cable on the battery ($8.99 at walmart).

While I was at it, I also changed the positive cable clamp. Afer I cut the old off I noticed quite a bit of corrosion, so I will be replacing the entire cable fairly soon.

No more blinking head lights or wobling volt meter. Thanks for the advice tho.

 

[TheRookie]

Yeah there is no reason you should ever even touch that screw. Usualy low or rough idle on the OHV is due to a bad iac.

 

[j602]

I agree with Rookie, definitely sounds like a dying IAC. Try cleaning it first. If it doesn't help, it may be too far gone to be fixed and you'll need to buy a new one.

 

[j602]

Also, how long has it been since it's had a tune up? Plugs, wires, filters.....

 

[Thelgord]

Actually I did an oil and lube job on it in Nov. It was the first thing I did after getting it out of the field it had been sitting in. This problem was a recent development, so I put new wires, plugs, and air filter in,along with cleaning the air intake sensor.

After that I changed the negative battery cable and positive cable clamp. This has stopped the blinking lights, and brought the Idle up to 750-800rpm, wich is probably acceptable, but if there is anything I am missing, like the IAC?

What is the IAC anyway?

 

[TheRookie]

Idle Air Controll.
Its on the upper intake manifold on the drivers side. has a 2 wire conector on it. 2 10 mm bolts holding it on.

 

[Thelgord]

Cool, Thanks a bunch I'll try that next.

 

[Makahveli]

750-800 rpm is that the correct idle?

 

[j602]

750-800 rpm is that the correct idle?

Pretty much.

 

[Thelgord]

Really? I would have thought it would have been closer to 900. Oh well, if it is correct then I will not try to get it any higher, although the bouncing volt meter has returned. Oh well, back to the tool box

 

[TheRookie]

The tach doesnt react verry fast to changing rpm. If you have a rough or eratic idle I would still look into this. THe bouncing volt meter is a sign