If it's not the IAC or TPS...what could it be?

[gearheadjlm]

Vehicle: 2004 Ranger XLT 4x4 4.0L SOHC Ext Cab Step side 5 speed w/129k

What's done to it: Flowmaster Catback, K&N Air Filter

No Check Engine Light (CEL)

Here's the issue: Say I am cruising or just trying to shift and the RPM is at about 1800-2200, When I push in the clutch (and let off the gas) the RPM's will jump up to around 3200 and hold for about 2 seconds, then drop to around 2500 for a second or so, then 1500 and then finally down to 800-900 (by this time I'm stopped). Speed, engine temp, and outside temp seem to have no effect on it.

I have tried to replace the IAC and TPS. I tried taking the Mass Airflow Sensor out and cleaning it with rubbing alcohol. I put new plugs in, and it didn't make a difference.

I am questioning EGR Valve, but am most expecting a hard to find vacuum leak. I tried spraying Ether (starting fluid) around vacuum lines and intake to see if I noticed a difference, and didn't.

Has anybody else had this issue? What else could it be? How else can I diagnose and find a vacuum leak?

Any help would be appreciated.

Here's some pics:

 

[98blownranger]

did you set the TPS for the voltage?

 

[gearheadjlm]

did you set the TPS for the voltage?

No, can you explain?

 

[98blownranger]

when the tps is removed it will change it postion. double check my numbers but .8 to 1 volt at idle and 5 at wide open....? it has been a long time. measure between two of the wires with 2 pins, to adjust you can lossen the bolts and rotate it some. I had the drill my holes larger when I install a bigger Tbody

 

[shadetree]

The TPS is not adjustable on his truck. Ford stopped using adjustable TPS in the late 80', or early 90's. The TPS, among other things, can cause an idle, surging, bucking problem however. Replacement is the fix as they do wear out.shady

 

[98blownranger]

no true my 98 you had to adjust it

 

[woodyedmiston]

Same problem

I replaced my throttle position switch after having some problems with the idle being too low. Someone on one of the threads suggested hooking it up, removing the battery connection, turning on the lights and then reconnecting the battery to reset the computer. That's what I did.

Nothing changed - the idle is still too low.

My TPS has no provision for adjustment (99 4.0 auto) but someone asked about the knob on the IAC - is that some sort of adjustment.

How do you adjust or should you have to adjust the tps on a later model?

 

[LEVE]

but someone asked about the knob on the IAC - is that some sort of adjustment.

The little knob on the end of the IAC stepper motor shaft is called a pintle.

The IAC helps to keep the air ratio correct. If it's in question, remove it and clean it, and it's mating hole. You'll likely see it is coated with carbon. If the IAC is bad you may see low or high idle, as well as erratic idle if the pintle is not closing the mating hole. That lets in more air, and the computer compensates by adding more fuel; the result is a higher idle.

For the problem with the jumping RPM's...

Have you checked the MAF sensor?

Did this problem start after you installed the K&N filter? There's been lots of talk about the oil sprayed on the K&N filter migrating to the MAF sensor. This coats the internals of the sensor.

The MAF is responsible for monitoring engine load; if it is dirty it may not be able to follow the engine load fast enough. That sends incorrect information to the computer and the RPMs do not fall with loss of engine load during shifts.

 

[98blownranger]

the adjustment for the TPS is done by rotating to sensor, you may have to drill the mounting hole a little bigger, If I recall correct you need .8 to1.0 at idle and 5volt at wide open. you measure between 2 of the wires use 2 pins to poke ito them.

IAC there is no adjustment and had nothing to do with a/f readings it controls the amount of air going past the Tbody

 

[gearheadjlm]

TPS was fine, IACV was fine. I searched and searched for vacuum leaks.

Checked out a TSB 05510 - High Idle Between Shifts.

Called for the computer to be reprogrammed. $80 bucks a my dealer, it's going in tomorrow morning...I am exspecting the issue to be resolved.

I'll keep you guys posted.

 

[jasonl]

Hope the reprogram works for ya. The only thing that can make the engine rpm go up (between shifts only) is the throttle plate being opened or the IAC going crazy. The only two things that can control the throttle plate are the cable going to the pedal and the one going to the cruise servo. The IAC is cotrolled by the PCM so I would guess that is the most likely source. Either the program has a glitch or your IAC is screwed up and taking the PCM input to new proportions.

 

[gearheadjlm]

problem fixed. The reprogram worked.

 

[98blownranger]

did you check you votage on your TPS? or just go get the program?

 

[woodyedmiston]

Iac

In my case I bought a brand new IAC ( $39 + tax at Autozone and bolted it on - cheapest locally) Stopped the problem.

 

[gearheadjlm]

In my case I bought a brand new IAC ( $39 + tax at Autozone and bolted it on - cheapest locally) Stopped the problem.

For this situation, that was the first thing I checked. Then I tried the TPS, then searched for vacuum leaks....

But the reprogramming worked and now the trucks runs amazing!

So I am happy, Now I just need to sell it and get a Gen II so I can finally build a V8 Ranger!