My 92 ranger, 2wd, 6 cyl, manual trans, is running at about 3500 rpm at idle. I was wondering what might be the cause, maybe something with the throttle or could the gauge be screwed up.

 

A dirty MAF can cause this problem. [Correction; I intended the IAC, Idle Air Control.] A dirty throttle body can cause idle problems as well. How many miles are on your truck. What has been done in terms of routine maintenance? Is the check engine light on? If so, go to an auto parts store and ask them to scan for trouble codes. Then post the numbers here and we can give you more help.

 

With the vintage of your ride & few clues, lots of possibilities, so maybe add a vacuum leak & acting out IAC to your idle speed woes.

If the problem came about suddenly after some event, look for a dryrotted, cracked, broken, disconnected under hood or in cabin vacuum line. If no joy there, look for a binding throttle cable or throttle plate as has been suggested & if no joy there maybe consider removing & cleaning the IAC with a plastic safe spray cleaner, like CRC MAF, or QD products, while keeping the IAC black cap & electrical connector oriented up, so the cleaning solvents & gunk it removes don't run in & cause other mischief. Cleaning the IAC may not last, it didn't for me but was a good trouble shooting step on my idle woes.

If you come to suspect a sticking throttle plate, remove the throttle body & carefully clean it with a coating safe throttle body cleaner that says its safe for coated throttle bodies. If you have to scrub the throttle body bore to remove deposits, do it gently with a nylon bristle brush or the like, so that you don't damage or remove the bore or throttle plate coating. Pay close attention to the plate OD/edge for deposits that'll cause it to stick in the TP bore.

If you clean the MAF sensor, if recently driven, let it cool before hitting it with the cold spray cleaner & use only a non residual plastic safe spray, like CRC or Valvolene MAF spray cleaner. Don't touch or poke the wire sensor with the spray wand & keep the sensor squeeky clean on instalation.

Seeing as how your ride is OBD-1, if auto parts stores cant scan your ECM, you can scan the computer for codes by following the EEC-lV instructions in the Emissions section of the Tech Info thread, located atop this forums thread index page. Then post up All trouble code Numbers, as they can offer up good trouble shooting clues.

After fixing your idle problem, disconnect the battery for about 15 min to wipe the computers corrupt fuel trim tables & idle strategy, then after the vehicle completely cools down, perform the cold & warm idle strategy relearn proceedure, to preclude driveability problems & to enable the ECM to begin rebuilding new uncorrupt fuel trim tables.

More thoughts for consideration, let us know how your trouble shoot goes.

 

It has 144K miles, the check engine light isnt on, and i just bought it recently so i dont know how well the maintenance was kept up. I'll start by checking the MAF sensor first.

 

The MAF sensor doesn't belong very high up on your suspect list, as it isn't responsible for maintaining idle speed, its responsible for reporting intake air flow into the engine, so the computer can use that input to adjust the fuel injector squirt time to control the air/fuel ratio.

Open/disconnected vacuum lines, open PCV valve or connecting rubber fittings, stuck open throttle plate, or misbehaving vapor recovery system can cause high idle woes & with your idle speed being as high as you report & with the vintage of your ride, a vacuum leak, throttle linkage, dirty/sticking open throttle plate, acting out IAC imo belong higher up on your suspect list than a dirty MAF sensor.

 

It doesn't matter is the check engine light is on or not codes can still be stored. Go get yourself an Equus/Innova 3145 code reader and pull the codes, this thing isn't expensive and it will pay for itself very quickly.

 

i took the TB off and it looks pretty dirty and the TP is pretty dirty and grimy so going to get some cleaner and see if that fixes it.

 

Good idea. You would do well to go through the entire air intake system, especially the IAC. Please note that I corrected this in my earlier post When I suggested cehcking the MAF, I meant to say check the IAC. Also, check out the PCV valve, if your engine has one. Try to locate the source of the dirt and crud in the air intake system. This will help on both the idle speed problem and improving gas mileage.

 

Well i cleaned the TB and TP and got a lot of the varnish and gunk that was built up around the TP, and i cleaned the throttle linkages and checked the PCV valve. I don't here any vacuum leaks and the hoses look fine so i'm going to check the IAC, running out of options here. I also noticed that i have a coolant leak where the thermostat housing is attached to the engine, getting a new gasket to fix that.

 

After cleaning up the air intake system, Does your engine seem to be running any better?

 

No it didn't seem to run any better, but now i have another issue. I took the radiator drain plug out and no coolant came out so i guess there is a blockage somewhere.

 

Before, doing anything else, remove the radiator cap. Is there any sign of coolant in the radiator? If not, try squeezing the upper rad. hose. Do you see any coolant moving thru the red. cap opening. Do you hear any swishing sound.

If none of this tells you anything, you may not have any coolant in the system or you may have a plugged drain. Remove the drain **** from the radiator and gently poke around the hole to see if that is where the problem is. If that doesn't tell you andything try removing the upper radiator hose and see if there is coolant there. If not, carefully remove the clamp on the lower hose where it attaches to the radiator, If there is no leakage, slowly remove the hose.

If none of the actions show any sign of coolant, fill the system with water and run the engine. What does the temp gauge show? Are there any indications that coolant is circulating in the system. With the rad cap off, do you see any coolant circulating? If not, add more water until you see or hear any sign of coolant circulating.

Let us know what you find and we will try working out a solution from there.

Good luck,

 

I removed the cap and there was coolant so i removed the upper hose and there was coolant there to. I poked around in the hole and nothing came out. I drained the upper hose and there is still a little coolant above the thermostat.

 

I removed the cap and there was coolant so i removed the upper hose and there was coolant there to. I poked around in the hole and nothing came out. I drained the upper hose and there is still a little coolant above the thermostat.

 

So you have coolant in the system. That's good. Since the drain hole is plugged, I sounds like you need to add a cooling system flush to your things-to-do list.

Keep "plugging" away at your growing list of things to do. Fortunately, some of those can be taken care of rather inexpensively.