Victim: 2000 ford ranger xlt, 5spd, v6 3.0, "trailhead" edition, 83k

Old Problem: Poor idle. Randomly idles low after decceleration (500 rpm). Sometimes idles high (12/1300 rpm). Both are usually corrected if I tap the throttle. Decceleration can be braking, or shifting to neutral and allowing to coast before the light with no brake.

New Problem: Same as before, but with new twist. If I use my AC, the idle will sometimes jump between 500 and 1200. I can be sitting at a light, and it will just start bouncing. Tapping the gas seems to correct at, as does turning off the ac

Symptoms: For the past few months, I have had an odd idle issue. It started about 5 months ago, so I did a tuneup consisting of oil change, spark plug, wires, and fuel filter. I also took it to my dad's shop and had it checked for codes as well as a diagnostic done with one of those awesome snap-on scanners. Everything came back good. No codes, nothign out of the ordinary.

Problem came back (sometimes it goes dormant for a week or so, as it did here). It has continued now for almost 5 months, now with the ac thing noted above. Seems to be pinging more now, and i have a feeling they are related

Solutions: I didn't want to just start throwing parts at it. MAF, iac, pcv, and egr system all tested fine. Problem seems intermittent, so I tried tapping on various components while truck was running. NO such luck making it reoccur. It seems like a vaccum problem, but I havn't found any leaks. With how its acting, I bet its some sort of vaccum component going out, or a bad computer. Suggestions? Truck is still driveable. Its not a major problem, just annoying and I actually have the time to deal with it now.

 

Sounds to me a lot like the MAF, but could be anything. Try disconnecting then connecting the battery and see if that does anything.

 

I agree with pintopower8, sounds MAF-y. As he said, disconnect the neg terminal and short it to the positive terminal, then reconnect everything. That will totally clear the system. Did you clean the IAC?

RP
Zach

 

Check the Throttle Position Sensor (TPS). You can check it with an Ohmeter to see if there is an "open" spot (wiring disconnected) or with Voltmeter with wiring connected. Center pin is "wiper", one end is ground the other is volts. Resistance or Voltage should vary up/down smoothly with throttle position. Look for a meter "flicker" as the throttle position is changed (best observed on an analog type meter). In some cases the TPS will not set a code because the throttle position changes before it stays in the bad position long enough to be detected.

 

IAC was cleaned, but had no affect. I have done the battery disconnect thing serveral times, doesn't help.

I will ask my dad how to further test the tps if I can't figure it out from what Piffery1 said. When we did the snap-on diag scan, the tps was the only figure not dead center in its range of variance, but was no where near failing.

 

In the "Articles/Specs" section of the Forum (see top of page) search "TPS" and you will find how to test it.

 

i had the same problem and it was the vacuum. my brakes didnt work as well either. check the back of your air intake for a bolt with nipples on it they might have like black covers on them. one of mine came off and it was leaking air. i went to the local parts store and they gave me $.98 piece to put on it and the problems stopped. Or your air intake could be cracked or have a leak.