IAC or TPS problem?

[WA 2 FST]

Truck has 12k miles on it. Went on a 4-day vacation, come back, fire the truck up (I drive it frequently, so it is not like its been sitting a month) and it wants to idle lower than normal.

Drove it a lot today, fully warmed up, and coasting to stop signs/lights, with the A/C on, it nearly stalls, to the point where the computer shuts A/C compressor off, as idle speeds read 400-500rpm.

Otherwise truck runs fine when in gear and cruising/accelerating.

In my years of working on late-model, EFI hot-rods, this is acting like a stuck or dirty IAC valve. But I did a search here, and a number of low idle issues seem to be attributed to the TPS. My experience with bad TPS's is that there will be a "dead spot" in its range, and you will feel this when accelerating.

So what do you guys think? Replacing TPS is simple, I can tell. I didn't really take a look at the IAC valve yet, although I can see the sensor. Is this something that is easy to remove/clean without having to replace a gasket of some sort?

Just looking for opinions before I take the time to rip into it.

 

[WA 2 FST]

I'm impatient, so I went out at 11pm, opened the garage door, turned on the garage A/C and pulled the IAC valve off. Sure enough the plunger was very, very sticky...not moving at all without some significant elbow grease. So I sprayed some carb cleaner on the plunger, soaked it pretty good and got it where it would move more freely. Cleaned out the oriface where the valve fits into the intake manifold.

Fired it up and, of course due to the carb cleaner, the revs shot to 2000rpm and then gently retreated to the correct/normal idle rpms. Revved it up a few times (the neighbors know the drill, but I try to be polite) and everything seems back to normal.

Will drive it around tomorrow to confirm.

 

[WA 2 FST]

Not that anyone cares, but maybe this will help someone down the road with the same problem.

Cleaning the IAC valve definitely fixed the issue. Now... it may start to stick again, and if so, I will just buy a new one (~$50-55, I believe), but it is a simple fix, and something to check before taking the truck to the dealer unnecessarily.

But at least my diagnosis was correct, and an easy fix to rectify what was a very annoying driveability issue.

 

[VIPR PWR]

Good info ,,, Glad you it worked .

 

[rare03srt10]

NICE! Thanks for the mini write up. Thinkin i wanna pull mine and clean it for sh!tz n giggles

 

[04viperram]

Yea me too.

 

[WA 2 FST]

Hope this does help someone down the road.

All you need is a Torx-25 socket head... I used a 1/4" drive with a 2" extension and then the T-25 head. Just two screws that hold them in...they have some sort of loc-tite type substance on them, so they come out slowly (a good thing really, b/c they are small and could be easily dropped down into the lower area of the engine compartment, and possibly hard to locate at that point). Then some typical carb cleaner which will not hurt the valve at all.

Understand, that it is a spring-loaded valve and it still should have some decent tension on the plunger. But mine was literally stuck and took hand-generated force to move at first. Since the carb cleaner is not really a lubricant, it is possible that over time it will stick again... however, in my experience on different vehicles with these same types of valves, they begin to stick b/c of carbon buildup. So that is easily removed with the carb cleaner. Spraying a little into the opening of the manifold and getting it all clean in there with a shop towel/rag is recommended as well.

There is no gasket on these, but a rubber o-ring which will stay on the valve as you gently pull it out of the manifold. Nothing to really worry about as far as it coming free from what I could tell, so no surprises there.

 

[rare03srt10]

To EASY!

 

[Floor]

my money would have been on the TPS.... good you ficed it.




PS: you have to be more patient sometimes, these buggers are older then you think:hmpf::flute:

 

[evanandretti]

Can you move the plunger in and out or will that damage it?

 

[yellowfever#154]

Just eliminate it. Im all about eliminating stuff we dont need.

 

[rare03srt10]

Just eliminate it. Im all about eliminating stuff we dont need.

Me too! Kinda like how i eliminated that heavy ass srt10 frame and used my light ram 1500 frame baa hahaaha

But on the real can we eliminate that sensor? How?

 

[WA 2 FST]

To answer one question above, no it will not hurt the plunger... just don't go ballistic with it. Once I realized mine was stuck/frozen, I sprayed carb cleaner on it and down into the plunger and that helped free it up. Then I did move it back and forth a few times.

Not sure about eliminating it. I'm sure it could be done fairly easily from a mechanical standpoint. Install a block-off plate, and plug the hose that reroutes air to the IAC bung. Remove IAC valve and tie up the wiring harness for the sensor. The issue there might be a PCM programming issue in order to keep it from throwing a code (if it does... not sure if it does... on older cars, I know it can throw a code).

 

[NVR2OLD]

I guess I'm not sure were the IAC valves is. Anyone have a pic?:dontknow:

 

[yellowfever#154]

IAC (Idle Air Control) is the do hickey that is to the passenger side (right) of the throttle body. It has a hose that goes to it and not sure where the other end goes at the moment as I eliminated mine a long time ago.

The purpose of it is to ensure a stead idle speed no matter the conditions (temp, altitude, etc)

To eliminate it is really easy. Take a hose (about 3-4" long) and put it on the nipple, then put a big bolt in the end of the hose to block it off. This is what I temporarly did with mine to get it to run on a factory tune with my camshaft (it doesnt idle so good). Then you can adjust your idle speed by turning in the setscrew on the throttle body.

In this picture look just below the throttle body and you can see some red tape blocking off a nipple. This is where the IAC is.

 

[THEWELSHM]

Where is the TPS Sensor?

thewelshm

 

[hawk02]

On the passenger side of the throttle body, 1 plug and 2 torx screws. just replaced mine 3 days ago to see if it fixed my surging problem at light throttle, it did.

 

[ZCx]

great lookin engine oil cooler lines:rock::rock::rock::rock::rock:

 

[THEWELSHM]

On the passenger side of the throttle body, 1 plug and 2 torx screws. just replaced mine 3 days ago to see if it fixed my surging problem at light throttle, it did.

View attachment 51903

View attachment 51902

Just did mine $25.52 cheap if it fixes that intermittent issue that doesn't really bother me:dontknow: Yeah right

thewelshm

 

[hawk02]

Good deal bud.........