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I tried to add this onto an old post that I had on the BB but couldn't find my old post. Thus, this update.
Heres the problem:
The car starts and runs fine. Usually. But, after you let off the gas pedal, and brake, or just let off the gas to slow down, you can see the idle drop on the tach to below 400rpm. And, once it drops below 400rpm, it will usually stall. Unless you anticipate it stalling and put your foot back on the gas. Then, it will rev back up again and not stall. It ALWAYS restarts after stalling.
However, it does not do this every time, but since I finally realized it appears to be a low idle causing the stalling problem, I watch the tach closely on deceleration. 7 out of ten times, the idle will bounce a little below the 500 RPM mark, then stall. According to the FAQ'S the 1993 940 T is supposed to idle at 775+or-. Mine idles at approx 600-650 in park. If it just had a stinkin' idle screw, I could just turn it a little and get the idle back up where it belongs. But nooooooooooo, they had to let the computer control it.
Here is what I have tried:
Cleaned throttle body
Cleaned Idle control motor. Also swapped it out with a known good one from a perfect running 240, still low idle, and stalled again
Changed out fuel inj. relay (before I realized it is idle related)
Changed out RSR relay " " " " " "
Checked every possible spot for a vacuum leak
Changed out AMM with a known good one, still stalled, same symptoms
The car has a new Crank sensor
The car has a new Power stage module
If I unplug the Idle control motor, it idles at about 1000rpm and doesn't stall. I have worked long and hard on this, and done lots of searching in the FAQS. Any help would be appreciated. What else is involved in the system that makes this thing idle, besides the icm, and the computer?
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OK I did the OBD test and there is some confusion.
DTM#1 code of 223. which table says signal missing to/from IAC. Cause: circuit fault to IAC or FAULTY IAC.( HOWEVER, when I ran DTM#3 the fan ran, injectors clicked, IAC also clicked, or energized.)
Cleared codes.
DTM#2 The TPS part of this test failed, (however, I think I have throttle screw out of adjustment, will adjust and re-test.)
This part of DTM#3 is where I got some confusing info. (bear with me, I haven't used OBD much, but followed directions.)
"remove the ignition coil center lead wire crank the starter, the engine will not start but it will turn over." I got a code of 1-1-3 (should be 1-4-1) on this part of the test.
Which the table says is fuel trim too lean?
The rest of DTM was confusing for me as all the LED would do was fast blink.
# Activate the following sensors. If the LED diagnostic code shown (note: this is not a fault code) is present then the sensor or component is OK:
* TPS OK in full load position (when throttle is moved from full load) 3-3-3
* TPS OK in idle position (when throttle is moved from idle) 3-3-2
* RPM sensor signal from ignition OK 3-3-1
* A/C control on/off OK (when a/c switch is depressed or released) 1-1-4
* A/C compressor start OK 1-3-4
* Engine idle speed compensation for automatic tran OK 1-2-4 (depress the brake pedal, move the selector to D and then to N.)
# Exit Mode 2 by switching off the ignition.
All the LED did was fast blink, and did not flash any codes, even when I did the part of the test of opening throttle all the way. But, I am confused about how you are supposed to "activate the following sensors" How are you supposed to activate these sensors?
DTM#3 As mentioned, fan ran, injectors clicked, and the IAC energized 3-4 times. Wouldn't this indicate that the IAC is good as is the wiring to it?
My check engine light has not come on through this whole ordeal.
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The only thing that catches my eye is you said it runs fine with idle control motor disconnected. Are you certain the 240 idle control is compatible with this year 940? Or is IAC truly fully functioning in 240... Maybe try a different idle control? Sorry, that's all I've got. Sounds very frustrating!
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740-DAN,
I haven't had much more time to dig into this but with the IAC disconnected, it runs at a little higher RPM approx. 1000RPM. This is at idle, and didn't try driving it with the IAC disconnected, only at idle.
I am sure the IAC that I swapped is compatable and a good one off my perfectly running 240 with same part#.
I believe now that the problem lies with the base idle setting, as I have not performed this adjustment yet. But, I believe this will get me straightened out, (or at least I hope so). This is a turbo, so it has the extra spool on the spindle, and there is some slop there that appears to possibly causing things to get out of spec. Thanks.
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Hi Jeff,
Check OBD codes, esp. for 311.
--
Art Benstein near Baltimore
Doing a thing wrong for a long period of time gives it the superficial appearance of being right.
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Thanks art, I'll check codes. I think I may have it narrowed down to base idle being off and needing to be reset, and possibly TPS adjustment. I always welcome your input.
Jeff
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Jeff,
Contrary to "andysbeta" there is no base idle adjustment for the LH2.4 system. The throttle stop is not for idle adjustment, base or otherwise. It is there to keep the throttle plate from binding. That doesn't stop many people from thinking otherwise. And I suppose raising the idle with the throttle stop keeps them from stalling, so they figure they did something right.
--
Art Benstein near Baltimore
Why do they sterilize the needle for lethal injections?
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Art, This is basically where I am at. I turned the screw until it was right on the edge of the TPS clicking, and it did raise my idle a tad. I realize this is just a quick remedy, and the real problem is still there, but for now I am going with it this way. Until I find more time to fool with it.
Let me ask this... There are lot's of ways to get this all out of wack, between the linkage rod adjustment, the stop screw, and the throttle cable adjustment, and TPS adjustment. Do I run a risk of making things worse if I start messing with the TPS? I never move anything like this without marking it first. But I said that about the linkage rod adjustment, and lost track of how many turns I had turned it
I am now thinking of adjusting the TPS, but have never had to touch one in 30 years of driving these cars. But, I remember it being a super touchy adjustment on an old 1974 SAAB that I had. The slightest movement, even tightening the screws that hold the TPS down would throw it back out of adjustment.
I can't imagine how it could ever get out of adjustment once it is screwed down, but the TPS on the LH2.4 adjustment sounds pretty cut and dried. And, hard to screw up. I think this may be where I am at, but don't want to get the TPS out of sync, but apparently, it isn't nearly as touchy as that old SAAB TPS adjustment. I don't think I can screw this up. From the FAQ...
5. Adjusting the TPS.
Loosen the TPS adjustment screws holding it to the throttle body. First turn the TPS clockwise (away from the electrical connector) until it stops. While keeping your finger on the throttle disk so it won't move, turn the TPS counter-clockwise (toward the connector) until you hear or feel a click. Continue turning until it stops, then tighten the screws. Go back to step 3 above to check the adjustment.
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Jeff, I think your car may have an unusual problem that just defies internet-helped DIY solutions. Beside that, I don't have a 940T. Don't drive over any railroad track in the meanwhile. :)
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Art Benstein near Baltimore
Raising teenagers is like nailing Jell-O to a tree.
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My 1991 240 has identical LH2.4 to my 940 T. The only difference I have noticed is the resistor pack on the drivers inner fender. I am doing the TPS adjustment. OK Art. I understand. I really appreciate all of the time you put into this. I will figure it out. Eventually. I am doing the TPS adjustment next.
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I did the best I could to explain my take on the throttle position switch adjustment in the TB thread:
I believe what I am reading here is the .15mm number ensures the switch is fully closed and not on the hairy edge when the throttle is shut. The .45mm gap means the engine control is given back to your foot as soon as there's definite movement in the throttle spool. Goes to responsiveness. Does it matter which is checked first just as long as both are correct in the end? In your case, the problem happens with your foot off of the pedal, right? For that, you want to ensure the .15mm part. Simply put, you want to be damned sure the switch is closed every time you lift your foot. Those switches aren't always electrically as snappy as they sound.
Asked again if you checked the OBD codes, too. I guess we are just on different wavelengths. Those folks on tbricks know their turbos. They asked you to dial up the throttle stop, and that's what's got you going. I don't know how to help any further.
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Art Benstein near Baltimore
The best place to be when you're sad is Grandpa's lap.
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Art,
Sorry if it seems that I haven't followed all of your recommendations. I have been sick as hell and it has been raining non-stop here and I have no garage. So, I get little snippits of time to work on it (Saturday is the only day it didn't rain here in weeks when I actually got to work on it for any length of time)
But, it only takes an umbrella and a few minutes to check the OBD right? I will check the OBD today. It is pouring rain here again today, and rain all day Sunday, and Monday.
I ran OBD with the plug in the #2 socket, the one that runs the fan, injectors, and IAC solenoid. I will go to the FAQS and find the correct OBD for my issue. Thank you for all of the help that you have given me over the years.
Jeff
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Is the check Engine light illuminated?
There is a reason that the idle is low. Either it doesn't have enough air, or it doesn't have enough fool.
If you unhook a vacuum hose, does it stall or does the idle increase?
The idle screw is worthless, and I don't like them. It is not needed, ever, if your car is running right.
Goatman
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Goatman, The check engine light is not on. But, just before the engine stalls, I noticed that the check engine light comes on first, then the rest of the dash lights as it stalls.
I will pull a vac line and see what the results are. Thanks
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