High Idle

[jpeek29208]

Hey all ,

Been trying to deal with this high idle issue and cant seem to figure it out. I thought it was the car being to cold, but that didnt make a difference

The car constantly idles at 1500rpm even once they car is warmed up and been driven for a while. Im running Maft Pro with speed density for a year now and this is a new problem

The car has no codes, the tps is adjusted correctly, and the isc is functional(according to tsrm). If i plug the ISC the car does not die, which means to me it is getting air elsewhere.

The air leak would have to be post tb correct? Should i just start replacing all the intake manifold gaskets? Any other advice or tips?

Thanks

Josh

 

[jdub]

You have to plug the ISCV line AND the PCV line...with both plugged it should die.

Does you TB have the idle bypass adjustment screw on top?

Assuming the TB plate fully closes at idle, the leak would have to be after it.
The vac lines are a common source.

 

[jpeek29208]

You have to plug the ISCV line AND the PCV line...with both plugged it should die.

Does you TB have the idle bypass adjustment screw on top?

Assuming the TB plate fully closes at idle, the leak would have to be after it.
The vac lines are a common source.

Yah sorry didnt mention that. I plugged both the ISC and PCV line and it still did not die.

Im not sure if it has a bypass screw. I dont belive that is the problem as the screw was never touched and it has never done this in the 5 years ive owned the car.

I will recheck the vac lines, but I did not see any problems with the few I have left on the car.Im thinking gaskets, after playing with it last night I can hear a audible air leak from the intake manifold side underneath the manifold, still cant pinpoint the darn thing tho.

 

[jdub]

There's a steel "vac line tree" below the intake manifold...the hot start VSV and EGR VSV attach to it (among others). A gasket leak is also a strong possibility. One thing is sure though, you have an air leak since the car did not die with the ISCV/PCV blocked.

The early ('87-'88) TBs had the screw...since '89 is a transition year, some have it...most do not. In any case, it should never be adjusted...it comes from the factory full closed and should stay that way.

 

[jpeek29208]

yah i dont have any of those vsv. I removed them a while ago. Im going to go ahead and replace the gaskets on the manifold all things point to that.

 

[jdub]

If you removed those VSVs, the vac lines leading to them have to be capped.
That also means you do not have an EGR...that is not a good idea.

 

[jpeek29208]

all the lines have been caped off when I removed it when i rebuilt the motor 3 years ago, so i know for sure that's not the cause as this is a recent development

 

[NTRA08]

the hose that goes from your ISC valve across your valve covers to your accordian tube. Pinch that hose and you idle should go down . If that works you have a faulty ISC. or disconnected. Check your linkage on your TB too.
you can take ISC apart and spray some wd40 in it. Sometimes they lock up and need some help opening .

 

[Grimsta]

I'm callin this one TB gasket. DO EET!!

If you want to check for your air leak, or torn gasket, you can use a smoke machine. But my prefered method is to take a can of brake clean and spray the sh!t outta stuff. Spray around both intake mani gaskets, spray the TB gasket, spray all your vac. hoses.
If you have a dip in idle or the car dies, inspect the area you just sprayed for torn gasket or hose

 

[NTRA08]

or just hook up an after market boost guage. start your motor. rev and watch if the needle shakes you have a boost leak. If so you might as well change all the intake gaskets because if you fix one more will come

 

[jpeek29208]

well i found my boost leak. it ended up being my intake mani -> head gasket. my old one was completely blown to pieces pretty odd.

but now ive got another problem and i know im over looking something stupid. the car wont idle now, but instead revs on it own. It made it to 5k rpm on its own before i was able to turn it off. Tb is not stuck open. would this be tps related?

 

[dumbo]

well i found my boost leak. it ended up being my intake mani -> head gasket. my old one was completely blown to pieces pretty odd.

but now ive got another problem and i know im over looking something stupid. the car wont idle now, but instead revs on it own. It made it to 5k rpm on its own before i was able to turn it off. Tb is not stuck open. would this be tps related?

what happens when you cover isc? what is your idle tps voltage? but if that throttle plate is closed that seems odd

 

[Grimsta]

Are you sure everything is bolted back on correclty? Make sure you didnt leave any ports unplugged. What did you take off to do it? Did you take the mani off in 2 pieces or all in 1piece?

 

[jdub]

Sure you routed/installed the TB cable correctly?
The TB plate should be full closed at the idle position.

If so, unplug the TPS and see if it still does it.

 

[jpeek29208]

I took everything off on the intake side. Replaced the lower and upper intake manifold gaskets. Replaced the TB, ISC, and EGR gasket. The tb plate is closed completely. Few days ago I also replaced the stock injectors with some rc 550s and rewired the O2 sensor due to the wires fraying apart.

Prior to me replacing the gaskets the car was idling high at about 2k, but it was steady. Now that ive replaced all the gasket(and the blown intake mani gasket) the car revs on its own to 5k rpm before i turn it off.

I know it has to be something stupid

Jdub,
Is it possible for the tps to be messing it up? Like the ecu thinks that I am at WOT, but obviously i should be idling. If i unplug the tps should it maintain a rough idle?

thanks guys,
josh

 

[jdub]

Info on the TPS...perhaps a high idle (not 5K RPM though) with it unplugged:
http://www.mkiiitech.com/forum/showthread.php?t=882

TB linkage per above?

Just to warn you, my patience expires pretty quick when a guy does not confirm what I say to do or answer what I ask

 

[jpeek29208]

Info on the TPS...perhaps a high idle (not 5K RPM though) with it unplugged:
http://www.mkiiitech.com/forum/showthread.php?t=882

TB linkage per above?

Just to warn you, my patience expires pretty quick when a guy does not confirm what I say to do or answer what I ask

The tb linkage is correct. Unplugging the tps sensor doesnt make a difference. I went back thru and dialed in my tps and its exactly to spec now.

The tb is closed at idle. They car is now idling at 2k and surging to 2.5k rpm. Ive noticed im running extremely rich ~ 10.5-11 at idle. Vacuum oddly is normal at around 20.

The only error code im getting is code 24, but ive been told this is normal for a maft pro speed density user.

Heres a video of what my car is doing, so you can acuatlly see it. sorry for the quality.

http://s2.photobucket.com/albums/y39/jpeek29208/?action=view&current=4c807edf.flv

 

[jdub]

I plugged both the ISC and PCV line and it still did not die.

Try doing this again to see if the engine dies.

It would be worthwhile to see if the accordion hose is sealed and all the hoses connected properly from the AFM to the turbo inlet.

Reset the ECU by pulling the EFI fuse....recheck for codes afterward.

 

[jpeek29208]

Try doing this again to see if the engine dies.

It would be worthwhile to see if the accordion hose is sealed and all the hoses connected properly from the AFM to the turbo inlet.

Reset the ECU by pulling the EFI fuse....recheck for codes afterward.

I justed tryed it and it acuatlly made no difference. I think i need to pull the intake mani again. The car has to be getting air from somewhere else.

Accordian hose is sealed and all hoses are connected. There is no afm tho, as im running speed density. Eveything pre tb doesnt really make a difference how the car idles for me.

i reset the ecu and i still just get code 24, which ive had since i installed the maft pro a year ago.

 

[jdub]

Didn't realize you were running SD. Block the ISCV and PCV fittings off at the respective fittings. Then block off the other fittings on the intake manifold...brake booster and big vac fitting on the front feeding the "tree" on the bottom. See what happens.

You removed the EGR correct? Is the EGR fitting on the plenum sealed off with a gasket under the block-off plate?

A long shot...did you check the intake manifold flanges (upper & lower) for straightness? Could be warped.