I recently cleaned the IAC Valve because the Wagon was running super rough during warm up. Now it still stalls out. Symptoms are: Cranks and fires with out even pushing the accelerator but during warm up it will struggle then die. After re-cranking it runs great forn a few the stalls a second time.

Am I missing something blatently obvious?

One shouldn't adjust the TPS without ensuring the throttle body is clean and the butterfly is indeed closing against the butterfly stop screw. Said screw is NOT to be used to adjust the idle...it is just to ensure the butterfly is closed but not so far as to stick when opening the throttle.

I've NEVER had to adjust a butterfly that wasn't messed up by an owner/shade tree mechanic...they're adjusted correctly at the factory nearly always. The issue is a dirty throttle body that won't let the butterfly close and someone adjusts the TPS so the switch closes on the slightly open butterfly. Of course then when the engine is warmed up it doesn't respond correctly when the throttle is opened.

John,
Did the Throttle body and FT and tubes today. Totally trashed with gunk. Got a slight problem now. Cars is idling at 2K RPM's. Could the TPS being off cause this? Could the timing be too far advanced. Do you think the like of PM in the past led to such build up that someone had adjust other stuff vice cleaning?
Please advise

Eric

What is the best way to clean it and do it poperly?

Can you hear your TPS click when the throttle hits the endstop? It's what enables the IAC function at idle.

My brother-in-law's newly acquired 240 had a rough idle which I cured in 5 minutes by simply adjusting the TPS.

--
David Armstrong - '86 240(350k km?), '93 940T(270k km), '89 240(parts source for others) near Toronto

Not sure how to check for that.

There's probably something in the FAQ, but with the engine not runninhg, have someone push on the accelerator pedal while you look under the hood. You'll see a cable pull on and rotate a pulley near the throttle body (where the air hose coming out of the air filter eventually feeds).

Now tell them to leave the accelerator pedal alone, and grab that pulley with your hand, and rotate it so it just leaves its endstop. You should hear a click as soon as it leaves the endstop, and again when you release it. If you do, then its likely OK, although knowing for sure that the computer is getting the switch signal is relatively more complicated. If you assume that the TPS function is OK, then cleaning the IAC is probably in order, especially if it's never been done before. Again, there should be something in the FAQ on this.


--
David Armstrong - '86 240(350k km?), '93 940T(270k km), '89 240(parts source for others) near Toronto

Hmm...Could it be the air mass meter? My wagon was stalling a lot, but cleaning the IAC seemed to fix it.

What is the IAC? I am having a similar problem with my 90 740.

The IAC is the idle air controller. It's a small, cylinder shaped motor that regulates idle speed. On your 740, it should be silver in color and it is located under the intake manifold. You'll notice two rubber hoses on it. There's also a harness plug on the front of it. See the FAQ for cleaning procedures. It's really an easy job. You'll need a can of spray carb cleaner. After I cleaned the one on my 740, it has yet to stall.

Good luck with it.

Dave

I found it, cleaned it and reinstalled. Still stalls during warm up. It's driving me nuts. It's not a huge deal but..
Seems like it is starved for air. The cleaner's good. CAn't find the PCV though? Any ideas

Hmm...By PCV do you mean the flame trap? I doubt that it would be the cause of the stalling. Does your 740 have OBD? Are you getting a check engine light?

Cheers,
Dave

NO engine light. Where is the flame trap on mine?

Eric

Eric,

The flame trap on your 740 is underneath of the intake manifold, towards the rear of the engine. Remember where the IAC is located? Go directly towards the back of the car from it and you will find a black plastic box bolted to the engine. It has a rubber tube with a plastic "Y" shaped connector coming out of it. Get a new one of these, along with the flame trap that's inside of it. You may also need to replace the rubber hose that connects the flame trap to the crankcase vent box. I'm not sure that this will help with your stalling problem, but it's a good idea to replace the FT as routine maintainance.

I can't remember if you already told me this, but are you sure that the AMM is okay?

Good luck with it.

Dave

Dave,
Found the FT. Really dirty but the actual FT is missing because the hose was not seated. I will pick up a new one in the morning. Does the "box" the FT connects to come off to be cleaned? Because that is saturated in old oily residue. Any more advise you can share would be great.
Thanks

Eric

Hi Eric,

Yes, pull that black plastic box, too. Be careful when removing it because the bottom part can break off. You'll need a new O ring for this box ( goes on the bottom b/w the box and the engine block). Once the box is removed, you can use spray carb cleaner and a screwdriver to clean it. Spray the carb cleaner into the box, slosh it around, and tap on the sides with the handle of a screwdriver. This will loosen the chunks of gunk that are inside. It takes a while to really get the thing clean, but take your time. That should help anyway.

Let me know how it turns out.

Dave

I will take care of it this weekend. Doing some other research. Turns out I need to check Fuel Press Reg. This little sucker can apparently cause alot of what I have been experiencing (stalling, poor acceleration). I want to do the Throttle body too. A little spring cleaning. I pulled the intake and that baby's thrashed too. Any cautions I need to take with cleaning it (carb cleaner and a tooth brush right?)
Let me know, and as usual thanks

Eric

Hi Eric,

I'm about to replace the FPR on my 240, too. It's leaking through the rubber diaphragm. The ideal thing to do with the intake manifold would be to soak in a parts washer or a giant tub of carb cleaner for a day or two. Those things can get some serious gunk in them. Just be careful when removing your injectors as they can be brittle. Replace the little rubber rings on them.

Dave

Today I got to the FT and the IAC and hoses. Firing up pretty good but idle is 2k RPM's??? Pulled the IAC hose and engine died as stated in FAQ
I have been consulting the multiple listings in FAQ's but they are addressed differently. Something wants me to think that the IAC is forcing to much air or my TPS got wacky when I pulled the throttle body and turned to on some spring cleaning
I want to know straight up how to fix the problem of the idle.
Got any pointers-
16v DOHC 1990 740 GLE w/ really high idle.
Also with the high idle now I have noticed when slowing to a stop at say a light the car bucks ever so faintly. At first I thought it was the brakes but they are prety new. Could the high idle be affecting vacuum and kickdown throughout? Standing by your your awesome, FREE, advise.

Eric

Hi Eric,

It's probably not the TPS if the car was idling okay before you cleaned the TB. Can you hear the switch click when you move the throttle? The problem is likely to be related to the IAC. When you cleaned it, would the valve rotate back and forth freely? Are you sure that all of the vacuum hoses are connected? It's been a while since I've looked at a 16 valve, but they're basically the same as the 8 valves regarding the things that you're working on. The bucking when coming to a stop is probably being caused by the high idle. The base idle screw (big black one on the bottom of the TB) won't help with that high of an idle.

Check it out and let me know.

Dave

Did you check for the TPS click though, as I suggested above? Your IAC might be perfectly functional, but it can't do its work, if the TPS doesn't enable it to do so.

As John B correctly points out, you shouldn't adjust the TPS without first ensuring that the throttle body is clean and adjusted correctly

HOWEVER

in a situation where the throttle body is dirty/maladjusted, such that the TPS is not enabling IAC function, a five minute test adjustment that does allow the IAC to function will most likely improve your idle significantly, until such time as you can deal with the throttle body service.


--
David Armstrong - '86 240(350k km?), '93 940T(270k km), '89 240(parts source for others) near Toronto