rough idle at startup, 204k miles

[Roadstump]

Hello all. This is my first posting after joining this valuable forum.

I have a 94 4.0 liter 2wd with 241,000 miles. I bought it new and put every single mile on it. It's a utility vehicle for me and I am about to hand it over to my 16 year old as his first car. Before I do I want to get it running as good as I can. It has several problems, none too serious, that I want to address but I'll take them one at a time.

The most pesky problem it has now is not wanting to stay running at a cold start up. I'm no technician so please forgive my incorrect use of terms. I am old school. It will start right up, even on the coldest days. Normal startup is a fairly high rpm until I either kick it down with the pedal or it warms on it's own, reminds me of the old automatic choke. What it is doing now is starting, high revving (normal) for about 5 or 6 seconds then rpms drop and it dies. It will continually do this until warm. What I have to do to overcome this is feather the gas when it starts to die to keep it running and the rpms up. Once warmed up it never has the problem again.

I have changed the plugs and wires but no joy. I bought a haynes but nothing really about automatic choke. I have no idea what you even call this. I also get an occasional Check Engine light when driving on local roads for no apparent reason (no change in operation, not accelerating or decelerating) and no I don't have a computer checker and really don't want to get hosed by the dealer to check it for me.

Point me in a direction and I will give it a whirl, as long as Haynes shows me where to find the part location.

Gary

 

[Lt.Jim]

Hello and welcome to the site. Most chain auto parts stores will pull the check engine codes for free. Start with that and you may find the problem. Also try cleaning the Mass air flow(mas or maf) sensor and the throttle position sensor(tps). These two are easy to do and usually have good results. Also, with the high milage, what is your catalytic converter like. It may be plugged up. And check your injectors. I doubt they would cause a high rev but may be restricted enough to cause the die out.

Do a search on this site theres lots of great info!

Good luck!

 

[Maniak]

The X uses the Idle Air Control (or is it Air Idle Control, I always forget the order so its IAC and AIC) instead of a choke.
That is what gives you the no touch start, and it also raises the idle when needed (cold, very hot, or a/c).

A long time ago our X wouldn't start correctly or stay running when cold. I'd turn the key and it would start then immediatly die. Once I changed the IAC it was fine.

~Mark

 

[marragtop]

You can also try cleaning the IAC. That works sometimes instead of replacing it. Do a search on for more info.

 

[93TwotoneXLT]

Clean the IAC and the MAF. The IAC is on the driver's side of the intake. It has a pin connector going into it and is held on by 2 bolts, 10mm if I remember right. The MAF sensor is located on the intake tube, right after the air filter box. Unplug the connector, then use a t-20 torx bit to remove the sensor from the housing. The torx screws on the MAF are a tamper proof design which either requires you to use a security head(ask the parts counter guy at your local auto parts store) or to get a small screwdriver and use it to shear off the security head on the screw, then just remove it with a regular torx bit. Buy some electrical parts cleaner and use it to clean the maf. Use some throttle body cleaner to clean the iac. Do a search of the forurms for the proper procedures for both of these small projects. If these two things don't cure your ails then check the #5 cylinder and see if there are any crusty deposits on the spark plug. It may indicate a leaky intake gasket that is allowing coolant and oil into the cylinder, and causing the misfire/stumbling idle you are experiencing. Hope this helps.

 

[Roadstump]

Success!!! Thanks for everyone's input. I removed and thoroughly cleaned the IAC valve. It was very dirty. My local auto parts had a product called Mass Air Flow cleaner which the clerk told me would work on the IAC as well and it did. I used a Q-tip to scrub the inside and then used compressed air to blow it out and dry the inside. I also carefully inspected the inside for any cotton fibers that might have come off during the cleaning. I stuck it back on, cold started it and my old 94 was revving and staying revved like it used to. Great tips here and thanks for all the advice.

I also cleaned the MAF afterwards as well as performed the TPS mod and she's purring like a kitten. Now to move on to a new posting for other problems.

Thanks again.

 

[Rustang©]

hey y'all two quick questions.

how do you clean the TPS?

how do you clean the MAF?

Thanks Guys.
I have a decent idea of what im doing, but i'd rather get the run through from people who know what they're doing.

 

[Roadstump]

After doing a search comparing notes from many different threads, then talking to the mechanic at the local parts/shop I cleaned the MAF by carefully removing the MAF. I say careful because there are these 2 small resistor looking sensors that are attached with some really fine wire and they look very delicate. I bought some MAF cleaner, but electrical contact cleaner is supposed to work fine also. I gave it a little burst of spray then took a Q-tip and soaked it in the cleaner and very carefully swapped each of the resistor looking devices down until the Q-tip remained clean. After that I gave them another rinse with the cleaner, shot them with some canned air to dry them off and reinstalled.

I don't know how you clean the TPS but did the modification to adjust for .96 volts. I didn't notice a huge difference with the mod but some people do. If you search for TPS mod on the forums you should come up with it.

Good luck...don't forget to clean the IAC though, what a difference that made.