[02yellowstanggt]

hey everyone i have a problem with my car idling, the other day i cleaned out my throttle body. Since i cleaned out my throttle body my idle seems to be a bit to high. when i'm stopped at a light the idle will hang around 1400 rpms, for 4-5 seconds then drop down to about 800 rpms. I have a bbk 75mm throttle body for more info, anyone know what could be wrong? any info would be greatly appreciated thanks. :bigthumbsup

 

[MelloStang]

did you also clean the IAC out? i would take it off and clean it out with some throtle body cleaner sounds like its sticky

 

[02yellowstanggt]

i will try that out:bigthumbsup

 

[02yellowstanggt]

the pipe that goes to the iac valve is humming, new problem now. any idea?:rollgrin:

 

[wmburns]

Sign it up for America's Got Talent?

Seriously, have you REPLACED the IAC? If not, please consider replacing. Cleaning is not always effective for IAC problems. Especially for the IAC with the black vent.

Check for vacuum leaks. Check the throttle return springs. Check for binding in the TB linkage.

Clean your MAF. Use only cleaner designed for the job.

 

[2oo5GT]

+1, cleaning it can only go so far. Try to clean the MAF and check the TB for sticking like mentioned.

 

[Brutal Metal]

sometimes cleaning the IAC will damage it, if that's your problem replace it with a new one!

 

[02yellowstanggt]

i got a new iac valve on order should be in tomorrow I'll let u guys know how it goes. Thanks for all the advice, appreciate it. :bigthumbsup

 

[MelloStang]

i have the same issue and replaced my iac it still does it the thing ive noticed is when it starts hanging up if i shut the car off and restart it its fine not sure if that helps im still trying to sort mine out

 

[86967]

i have the same issue and replaced my iac it still does it the thing ive noticed is when it starts hanging up if i shut the car off and restart it its fine not sure if that helps im still trying to sort mine out

This is almost always the throttle body or linkage...a custom tune can also adjust idle speeds

 

[wmburns]

i have the same issue and replaced my iac it still does it the thing ive noticed is when it starts hanging up if i shut the car off and restart it its fine not sure if that helps im still trying to sort mine out

To me this says one of two things. Bad TPS or loose/worn/leaking throttle body linkage.

IMO, the heart of the issuse is that the PCM is not getting a reliable closed throttle signal. The PCM does not "know" that the throttle is closed, a high idle results.

Further, suspect that the TB idle adjustment screw has been altered in an attempt to correct this problem. The adjustment is set too high allowing too much air to pass.

The other clue is that it improves when the car is shut off and restarted. Remember that the PCM "re-learns" a new closed throttle TPS value each time the car is started.

Start first by checking the throttle body. Check the return springs. There should be two and they should be strong. Check the TB linkage. Should move freely without binding. The TB MUST return to the same position each time the TB is closed.

If no problem is found with the TB, then it is possible the TPS is bad, loose, or noisy.

This is important to understanding the problem! The value of the TPS sensor does not matter. What matters is that the SAME value is sent each time the throttle is closed.

The easiest way to confirm this is with an ODB2 scanner. Monitor the TP-MODE PID. Confirm the value of closed-throttle (C/T) each time the TB is closed. Only when the TP-MODE = C/T, and the car's speed is zero, will the PCM enable the slow idle process.

 

[02yellowstanggt]

i got a chance today to install the new iac valve and the idle is still hanging. i have a feeling its the actual throttle body. I got the bbk 75 mm tb. ive heard that there tb's have a coating on them on the inside, and if you rub the coating off it effects the idle, anyone heard of this or is this a false statement?:nono:

 

[02yellowstanggt]

btw thanks for all the info guys:bigthumbsup

 

[wmburns]

i got a chance today to install the new iac valve and the idle is still hanging. i have a feeling its the actual throttle body. I got the bbk 75 mm tb. ive heard that there tb's have a coating on them on the inside, and if you rub the coating off it effects the idle, anyone heard of this or is this a false statement?:nono:

So. just wondering if you have looked at any of the previous information? Since you have an aftermarket TB, how did you set the idle set screw? Did you follow the manf instructions?

Suggesting, try closing the TB set screw in small increments.

Also, what happens when the IAC electrical connection is disconnected? Does the idle slow or the engine die? Or does it continue to run at the same speed?

 

[02yellowstanggt]

i'll try adjusting the tb screw. the aftermarket tb was on the car when i bought it, cant really say if its set at the right increment. when i unplugged the iac valve the car wont run on its own. it'll only run when im giving it some gas.

 

[wmburns]

If it dies or won't run without a little gas with the IAC disconnected, the TB idle set screw is in the ball park.

The two primary causes from here are a vacuum leak after the TB. Are you sure there are no vacuum leaks after the TB? What about the vacuum hoses? Valve covers? Oil dip stick? Oil filler cap? Hoses? Here's an important one. PCV valve or grommet. How old? Leak free?

The other possible cause is a bad/loose/nosiy TPS. Do you have an ODB2 scanner that can monitor ODB2 operational data?

 

[MelloStang]

i can say i reset the idle with the ford motorsport prcedure so the idle screw isnt my issue and i pb blastered my throttle body and its free as a daisy my value is in the ball park at 90 at idle but its continually hangs up today on the way home it was fine till i got off the highway then it was 1600 rpm and between shifts was a hoot it was trying to power shift for me i replaced my iac and my codes are 44 and 94 wich is the smog pump and i have a 67 at koeo

 

[wmburns]

I think there are possibly two very different issues going on here.

Mellostang; what model year car are we talking about? Your profile would indicate this is a Fox body. The way the IAC/TPS works on a pre 1996 is very different from a 1996+. The TPS plays a very different role. As such, it is far more likely to cause a high idle.

02yellowstanggt; IMO the most likely reason for your handing idle is a vacuum leak. Assuming that there are no obvious vacuum leaks, then it is possible the leak is in a location not as easy to spot.

Consider getting a propane based leak detector. Amazon sells an affordable unit.

Amazon.com: Vacuum Leak Detector: Automotive

I personally don't like to spary carb/choke cleaner or brake clean all over a motor in an attempt to locate vacuum leaks. The solvents can damage the intake gaskets thus trading one problem for another. However, many ppl have done it without apparent problem so it's your project.

Use the leak detector around the PCV grommet, valve covers, intake gasket, and throttle body. Pay special attention to the area around the TB linkage and the TB and upper intake plenum gasket. Work around the motor until all areas of possible unmetered air entry have been tested.

Probe around the EGR system and the EVAP purge lines as well.

If the leak source is found, the engine RPM's will increase as the propane is ingested.

The propane will not leave a residue or damage any components. Short of a dealer grade smoke tester (best method), this is the most affordable method to locate a difficult engine vacuum leak (IMO).

 

[MelloStang]

i have an 88 gt with speed density

 

[02yellowstanggt]

think i found my vacuum leak. i noticed a little oil around the pcv valve, on the passenger side. i think its the original pcv valve, ive never changed it when ive had the car, so this could be a contributing factor:bigthumbsup