i have been diagnosing the high idle problem on my 10AE for some time now. tonight i am looking more closely at the throttlebody and notice that the throttle stop is not against the stop screw. this means that the butterflies are not closing properly. when the throttle cable is pulled and released it sounds and mechanically feels like the butterflies are closing all of the way. the dashpot rod is even extended. what can i adjust or look at to remedy my problem? here are the pics:

 

With the thermowax system on the car, the throttle will not be closed if the engine is cold. It holds the throttle open slightly to maintain high-idle until the car starts to warm up. Once warmed up, it will allow the throttle to close like it should.

If it is fully warmed up but the plates are not closed it could be 1 of 4 things:

1) The coolant level is low enough that water doesn't pass through the thermowax.

2) The tiny coolant passages in the thermowax are blocked, preventing it from seeing warm coolant.

3) The screw right beside the dashpot may need to be adjusted. The FSM tells how to adjust it.

4) The throttle cable may be adjusted too tightly. In your picture, it looks very taught, usually it should droop slightly.

Hope this helps,
Vincent

 

vince, the throttle cable is ok, as i just adjusted it this evening. from what i understand, the screw by the dashpot is the throttle stop screw and from my understanding, it shouldnt be touched. i wont rule out the thermowax but unfortunatly dont know much about it so i cant determine if its working properly.

 

As mentioned, when the engine's cold the thermowax will hold the primary throttle open a bit. This is normal.

If you want to check this, lifting the linkage on top of the thermowax will disengage the throttle from the fast-idle cam and it'll close to where it would will sit with the engine hot. Do that and you'll probably find the throttle closed against the stop screw.

See page 4B-62 in the FSM Fuel System chapter for a pic of the linkage.

 

In your first picture http://i218.photobucket.com/albums/c...f/DSC06223.jpg look to the right and about three quarters of the way up. You can see a screw/spring. Lift up on that screw/spring and I *think* you'll be doing what the NZ suggested. When you lift up the GAP should close at the stop screw.

Note how that screws end is resting on the top of the Thermowax's piston. When the thermowax gets hot, that piston rises and pushes against that screw/linkage and does the same thing as what your about to do with your finger.

 

Correct.

 

ok, thank you both for the advice. i did as suggested and the throttle did not close. what does that mean? should i replace the throttle body? here are some pics:

 

Put on spring on it. One time after cleaning out my throttle bodies they kept sicking open so i put a spring on there and after about 500 miles removed it and it was working fine.

 

well, the problem is that even if i apply force to the throttle stop the throttle wont clost

 

my throttle body is off and the back side is pretty dirty...anyway was wanting to know what people used to clean this off...carb cleaner/maf cleaner? everything safe? not trying to steal the thread but its still kinda on topic

 

oH.... that sucks turbo or NA? Series 4 or 5? Ill I think i have a s5 turbo one somewhere i can sell you for $50

 

Nevermind i see its a 10th AE...

 

ok, i removed and replaced the throttle body and the engine idled at 800rpm. it fluctuatd for a sec and stalled once. i restarted the engine and gave her a couple of revs and she settled in at around 1200rpm. i let the engine warm up to normal operating temp and the idle increased to 1300rpm. i let the engine cool after shutting it off and restarted it and it idles at 800rpm. i reved it to 4K and now we are back to 1200rpm. i was looking at the old throttle body and lifted the screw above the thermowax and the throttle closed the rest of the way. when it was on the car it did not. i checked the throttle cable and cruise slack and they were fine. i adjusted the tps and it changed nothing. i didnt even get a fluctuation in idle.

 

i'm open to any suggestions as to why the idle could be so high still...

 

It has SOMETHING to do with that business where you lifted that screw and the throttle closed all the way but when on the engine lifting the screw has not the same effect. Odd.

One way to overcome this is to turn that screw all the way clockwise til it bottoms out. The cam/roller should seperate and the throttle should hit the stop once more, never to return to the gap again. Try counting the number of turns you make and write it down for future ref. This also means the thermowax is now ineffective for the future. Won't work anymore because in effect it's now fully extended when cold or hot (in a manner of speaking).

Again I write this.............once a engine speed creeps over about 1100rpm, the ECU advances the timing. When that happens the rpms go up around 1300rpm. But I agree it's the idle speed that is causing the creep up to 1100rpm.

Try this the next time the engine is hot. Remove the bac plug and see if things stay the same or NOT. If now the idle drops to below the 1100rpm and stays down after you rev the engine, then try cleaning the bac. IF removing the bac plug has no effect, leave the bac alone and don't fool with it. I've seen a bac with a slight sticking problem cause the idle to stay around 1100 rpm. This idea should come after making sure the throttle comes against the stop screw First. First things first.

 

i have removed teh BAC plug with teh engine running and up to normal operating temp. no change. as a not, on the "new" tb, the clear extension with the veccume lines that threads into the rear of the throttle body is not present. never was one there. i believe the tb is a jdm one that i had came on a jdm engine that i bought. i am going to work on the car now.

 

my "new" tb looks like this: http://fc3spro.com/TECH/HOWTO/TBM/tb02.jpg

i'm going to go out and pull the intercooler and verify the position of the throttle sop in relation to the stop screw. this should give me something to go by, as the old throttle body's stop would not close on the car. as a note, the gas pedal is not as easy to press down as the one on my brilliant black TII. the one on my AE is not stiff by any means but somewhat feels as if the cable inside of the sheathing is rusty... it doesnt appear to hold the throttle open though....

 

************************************************** ************
extension with the veccume lines that threads into the rear of the throttle body is not present******************************************* **********

Water thermo valve that controls the double throttle action when the engine is cold.

************************************************** ***********
i'm open to any suggestions as to why the idle could be so high still...
************************************************** *********

Throttle still not hitting the throttle stop screw?

 

i am going to verify that now and i'll post back with a pic. be back in 5 mins.

 

ok, uploading the pics.....the stop is dead set against the set screw with teh engine cold, as it has not been run since last night. pics will be up shortly.

 

old tb:



new tb on the engine:

 

i wonder if the accelerator cable is binding and is just cracking the throttle open. it doesnt bind when i operate it at the throttle body but maybe its binding when i press the accelerator pedal.

 

Might be.

Ever try to work the throttle from the engine bay to see if things change?

That sure is a different throttle stop screw on the *new* throttle body. Has a spring and all. Maybe back it off a bit and see what happens? Just remember how many turns etc. Shouldn't take more than a half turn or so to make a difference if that is holding the plates open.

Did you ever try the idea I suggested about warming the engine up, putting it in gear and slowly letting the clutch out to more or less stall the engine down below the 1100 rpm, and then putting the engine in neutral and seeing if the rpms stayed down or not.

Good pictures of the throttle body. I'm going to save them for the next time someone asks where the stop screw is or where the thermowax is etc.

Have you sprayed around with starter fluid to find vacuum leaks? Probably did.

Ever try using some PCC pipe in lieu of the intercooler? You run the PVC b/t the turbo outlet to the throttle body inlet. Then you can make adjustments to the throttle body without taking the intercooler off and engine running.

That's really a difficult problem of yours to fix online. Could be something as simple as the crack in the turbo inlet duct at the turbo or something similar.

 

well, i hadn't tried putting the trans in gear and letting the clutch out. and i want to make a pvc piping "intercooler" for testing and diagnosing problems but i havent searched to find what i will need to do so. my lazy fault there.

i did try backing the stop screw off a bit and no change was evident so i put it back the number of turns that i had counted. actually, it was only 3/4 of a turn.

i did try the starting fluid test. nothing there. my turbo inlet duct isnt in teh best of shape. i repaired it with silicone and wrapped it in super 33 for a tight seal. i then let it dry and installed the clamp. it is a little sung but can be removed and installed by hand. i didnt know if it woud lead to any problems in its current condition. at any rate i'm well aware that i need a new one but i just dont have the cash to buy a new one. the thing that really erks me is the tightnes of the gas pedal. maybe i should look into a new cable.

also if there's an angle of the tb that you would like to see i can snap a pic and post it so you can use for later reference. it would be nice to help someone out in the 2nd gen section rather than ask questions all of the time. i've spent most of my time in the 1st gen section as i have 4 FB's 1 SA, and 2 FC TURBOII's. i can fix what feels like anything on a first gen with my eyes closed. the FC is a little more complex but they're such wonderful cars!!!

 

You seem to be concerned about the throttle cable. Maybe just get the engine hot and then go to where the cable attaches to the engine on the back of the throttle housing and loosen up the jamnuts there so you can put more slack in the cable.

NZCONVERTIBLE posted a pictue of the PVC piping.................somewhere.

Just a little FYI. Idle timing is minus 5 and minus 20 at idle. If the rpms are advanced slowly to above approx 1100, the timing goes to plus 13 for both lead and trail. Just some input that might help someday and to give you an idea of how much your ECU has advanced the timing by beihg above 1100 rpm. It's hard to pin down the exact rpm it advances, but 1100 is with in 50 rpm if memory serves.

I think I'd look at the OLD throttle body and look into the throttle bores while lifting that SCREW up and try to figure out what is holding that one off its stop.