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update--stalling at start, then idles pretty well? 700 1989 700

posted by Tyler on Thu Jul 30 08:54 CST 2009
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last visit: Fri May 7 09:14 CST 2010

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I installed a new fuel filter and check valve (the check valve was toast). No improvement on the start of this car. It still wants to stall when first started, but if I keep my foot on the pedal so the rpm is like 1000, after about 30 seconds the rpm will rise on its own to about 1200-1250, then the car runs fine. After a normal idle, though, if I throttle the rpm to maybe 1500, then let off, the car wants to die. The idle goes so low, without recovery to normal, that it just runs down and quits. However, normal driving it runs fine. If you punch the pedal the car wants to fly:):)...
Just not sure where to look. I started this post as the previous was getting a little lengthy. I have checked for vacuum leaks, removed and disassembled the IAC (it was clean, and bench tested just fine), replaced the main intake hose from AMM to turbo, checked throttle linkage, removed and cleaned the throttle body.
Thanks for any suggestions--Tyler

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update--stalling at start, then idles pretty well? 700 1989 700

posted by Will740turbo on Thu Jul 30 13:55 CST 2009
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last visit: Wed Oct 22 16:09 CST 2014

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My first step would be to run the TPS test in the diagnostics mode with the OBDI setup.

It can tell you if it ever detects that it's at idle (and should therefore use the IAC). You can also check the set-screw for the throttle plate. It should be set to keep the throttle plate closed, but could be holding it open enough that the TPS doesn't ever connect at the idle position. Also could be the pigtail on the TPS.

Post back and good luck,
Will
--
1990 740 Turbo, on its way to stock specs, maybe beyond

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update--stalling at start, then idles pretty well? 700 1989 700

posted by aleekat on Sat Aug 1 04:58 CST 2009
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last visit: Fri Oct 24 13:19 CST 2014

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Being an 89 turbo, very limited OBD.

http://www.brickboard.com/FAQ/700-900/ElectricalIgnition.htm#OBDTechniquesBosch22
--
Post Back. That's whats makes this forum work.

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update--stalling at start, then idles pretty well? 700 1989 700

posted by Tyler on Sat Aug 1 04:11 CST 2009
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last visit: Fri May 7 09:14 CST 2010

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OBDI? Not sure what this is. I'll double check the linkage, signals to from TPS, etc. Good point! Thanks!

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update--stalling at start, then idles pretty well? 700 1989 700

posted by spasske on Sat Aug 1 06:26 CST 2009
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last visit: Thu Oct 23 10:11 CST 2014

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The Turbos did not switch to LH2.4 Jetronic fuel injection which has OBD I (On Board Diagnositic I) with some diagnostic codes until 1990.

--
Paul NW Indiana '89 740 Turbo 140,000

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update--stalling at start, then idles pretty well? 700 1989 700

posted by Tyler on Sat Aug 1 09:40 CST 2009
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last visit: Fri May 7 09:14 CST 2010

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ok.....went to recheck all linkage, tps, etc etc. Then went to search on the TPS and found this from another post, WHICH CURED THE PROBLEM:

"Idle speed is adjusted with the bypass valve on the throttle body (black knob). Either ground the test wire or squeeze off one of the IAC hoses to disable auxiliary air. Turn the black knob in/out for 650-700 RPM on warm engine. Remove grounding wire or hose blockage. You're done."

It was the thumb wheel adjustment that was causing the whole problem...duh.

Thanks all for helping me make this car run really well.

Tyler

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update--stalling at start, then idles pretty well? 700 1989 700

posted by Will740turbo on Sat Aug 1 09:48 CST 2009
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last visit: Wed Oct 22 16:09 CST 2014

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Sorry for not noticing the OBDI limitations. I didn't see a year and just assumed it was 2.4 (not the best approach).

You adjusted the idle with the set-screw? AFAIK that's not the best way, but maybe I'm wrong? Does the IAC move when you move from part throttle to none?

-Will
--
1990 740 Turbo, on its way to stock specs, maybe beyond

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update--stalling at start, then idles pretty well? 700 1989 700

posted by Tyler on Sat Aug 1 09:59 CST 2009
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last visit: Fri May 7 09:14 CST 2010

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No, didnt adjust the idle set screw, but used a pair of vise grips to choke the air coming through the IAC. That killed the car! So I arbitrarily adjusted the thumb wheel OUT and tried it again. Car didn't die. So I fine tuned the thumb screw/wheel until the tach read about 650-700. I released the grips, and then went to throttle up and took my foot off the fuel and the transition from high rpm to idle went very smoothly. Stopped the car, let it cool down and went to start it, it started normally, and didn't die.

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