Cleaning the throttle body gone bad

[BIGSLVRXJ]

1990 AW4 4.0.I cleaned my throttle body today(I left it in the vehicle) and now its idling at 1500-1700. I used O'Reilly's TB Cleaner. Did I screw up the IAC or the TPS or something else. I replaced the TPS like 2 months ago but it has a lifetime warranty. The IAC I've never replaced. Has this happened to anyone else?

 

[8Mud]

The last time I cleaned my throttle body, I removed everything but the TPS, wraped it in a piece of plastic. Tried to save a minute, cost me a TPS. Really have to remove the throttle body, the TPS and the idle motor, to do it right. The idle motor (IAC) , air passeges, usually take some scrubbing, to get clean, even with a good solvent. The TB gasket gets hard, often doesn´t re-seal well (need a new gasket). There is an idle air adjustment screw behind a press in cap, the air pasage at the screw is pretty small. Takes some work to get it clean, a spray and pray, probably isn´t gonna get it clean.
Another down side to cleaning on the vehicle is, oil and solvent puddle in the rear of the intake manifold. There is a slight U shaped section in the manifold that can collect oil and solvent. And nobody really knows, what the solvent and junk moving through your motor is doing to the O2 sensor (could have a chemical and/or oil coating). Hope the label on the cleaner you used said O2 sensor safe, hope they weren´t lying if they said it was safe.
Could have something stuck in the IAC piston or maybe you have a vacumn leak that was plugged with junk and isn´t anymore or your O2 sensor is coated in something. TPS sensor is often suspect, with idle problems, as are vacumn leaks and sometimes the O2 sensor.
I have a slightly flaky MAF sensor (or connector), that messes with my idle on occasion.
If I had to guess, I´d guess junk in the IAC piston.

 

[BIGSLVRXJ]

Well I just tried to clean the IAC and it did nothing. I sprayed it all out and it still idles at 1500. Something is messed up. I wondered if I completely killed the IAC or what. Anyone else have an idea?

 

[8Mud]

The first time I cleaned out my throttle body, it had just come from the dealer. The IAC was jammed with crud. I cleaned everything and it idled well above a thousand, noticed the stop tab for the throttle was bent. Figure the guy at the dealer (instead of cleaning the IAC) had adjusted the idle by bending the tab. Took me awhile and a few TPS adjustments to get it right. Changing the throttle stop, changes the TPS adjustment.
Did you remove the IAC and clean the seat, I had to scrape mine out last time, stuff was baked on there, some serious carb cleaner didn´t hardly touch the crust.
You can look down the air passage (for the IAC) from the top of the throttle body and watch the piston for the IAC, move in and out with a flashlight.

 

[NCSUcherokee]

make sure you didnt leave the vaccum line that runs from the TB to the map sensor off, that can contribute to an idle problem.

 

[Neil]

I have found that every time that I get the TPS wet I have to get a new one. Kinda sucks

 

[Dr. Dyno]

make sure you didnt leave the vaccum line that runs from the TB to the map sensor off, that can contribute to an idle problem.

There isn't a line from MAP sensor to TB on pre-'96 4.0's. The vacuum line from the MAP sensor goes directly to the intake manifold.
jeepguy1990, I suggest that you disconnect the negative battery lead for a few minutes to reset the PCM and then see if the idle speed drops back to normal.

 

[BIGSLVRXJ]

Unplugging the negative cable did nothing. Thanks for the tip though, but I think I found my problem. I unplugged the IAC while the engine was running and the RPMs didn't change. If it's plugged in they are at 1500 and if its unplugged they stay at 1500. So... I think that means the problem is the spray I used cost me an IAC. Any other thoughts on this?

 

[CharlesS]

Unless there is something stuck in between the seat and disc of the IAC.... By disconnecting the IAC and the high idle still exists.... I believe that the TPS is your problem...

Charles

 

[martin]

You need to spray cleaner down the IAC passage until it runs clear instead of brown. You need to pull off the throttle body and spary. Also take a brass brush and clean off the back side of the butterfly.

You could have a bad IAC but I'd make sure the passage is clean. If your XJ has over 100,000 miles then replacment could be considered a fair wear and tear item. I replaced my IAC at 150,000 and it fixed the engine would die when you coast down on the highway.

You can pull off the IAC, it only held on with 2 bolts and you could see how clean it is in the passage. If the passage if full of gunk then you know a good cleaning is in order.

 

[BIGSLVRXJ]

The passage was relatively clean even before I sprayed it but now its REALLY clean. My IAC motor has never been replaced to my knowledge(my knowledge is the last 6 years) so I'm thinking the cleaning might have done it in. Again my TPS was just replaced about 2 months ago with a Borg Warner lifetime warranty one, but I guess the lifetime doesn't make it invincible. I'm really leaning towards my IAC but if more people think its my TPS maybe its that. Anyone else?

 

[johnnyc]

When you took the IAC off, did you make sure the piston goes in and out smoothly? At the end of the piston (at least on mine), there is a small screw that holds on a sleeve. Under the sleeve is a spring. Take it apart and see what you can see. You can't muck it up any further than it is.

I also had a high idle after cleaning. Messing around with the screw and spring fixed the problem.

 

[BIGSLVRXJ]

I just kind of messed with the screw and spring and sleeve but it only made it idle higher. Im not sure what the "piston" is but is it the part that the screw screws in to, if so that isnt moving at all.

 

[Neil]

The passage was relatively clean even before I sprayed it but now its REALLY clean. My IAC motor has never been replaced to my knowledge(my knowledge is the last 6 years) so I'm thinking the cleaning might have done it in. Again my TPS was just replaced about 2 months ago with a Borg Warner lifetime warranty one, but I guess the lifetime doesn't make it invincible. I'm really leaning towards my IAC but if more people think its my TPS maybe its that. Anyone else?

I bought a new TPS and pressure washed my engine 3 weeks later and toasted it. They are very touchey and can contribute to the problems that you are having. My vote would be for the TPS.

Neil

 

[jneary]

its hard to tell without knowing what the tps is reading. was the throttle body gummed up bad. there is a little allen head set screw you can adjust where the idle stop is but if you adjust that you would have to reset the tps because that would change. but it does semm like the iac is just jammed, and if you fooled with it it could be bad now.

 

[BIGSLVRXJ]

The thing is the spray didn't even come close to touching my TPS so I dont know why the problem would be that. However I'm sure I did hit the IAC with it. The throttle wasnt gummed up horribly no.

 

[BIGSLVRXJ]

This is frustrating the heck out of me. I replaced my IAC today and that wasn't the problem, it made no difference. The only other thing I can think it would be is maybe the TPS which I'm also going to replace tomorrow. Is there anything else it would be?

 

[XJEEPER]

There isn't a line from MAP sensor to TB on pre-'96 4.0's. The vacuum line from the MAP sensor goes directly to the intake manifold.
jeepguy1990, I suggest that you disconnect the negative battery lead for a few minutes to reset the PCM and then see if the idle speed drops back to normal.

SPOBI alert!! Sorry Dr, my 89 has the MAP sensor vac line plugged into the throttle body. Occasionally this line wiggles loose on the TB end, which causes the Jeep to run like crap. Not really sounding like this is your problem though.

 

[BIGSLVRXJ]

This thread has strayed a little from my tb cleaning experience, but..... I've now replaced both my IAC and TPS and its still idling at 1500. I now recall one other thing that happened when my engine was shut off at the same time I was cleaning the tb. My emissions vacuum harness(the front one)(CCV?) is very old and hard and it seems that a piece of it broke off that attaches to a very strong vacuum source. When it is unplugged it idles even higher like up to 2200. Im thinking that that might be it. I have it rigged right now with duct tape but I think the tape is letting some vacuum by and thats whats causing the high idle. On the engine half of the front vacuum harness there is the line that goes to the egr vac. trans. and the line that goes to the front hole in the valve cover. Besides that there are two lines that go to something on the intake manifold. The one that plugs into the top port on the intake manifold is broken. Would that cause my high idle even with it duct taped?

 

[1989laredoxj]

I had a similiar problem after cleaning the tb. Turns out I didnt connect the wires tight enough which was causing a high idle. tps and idler stepper motor may need replacing but i didnt and it turns out it was just the connections...