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Idle Issues on '94 940 Turbo 900

posted by  MisterBLC on  Tue May 15 12:11 CST 2012
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last visit: Tue Aug 26 14:55 CST 2014
[RELATED]

Everyone,

I have been slowly working on doing a "stage 0" on my wife's '94 940 Turbo w/ 220k and I am continuing to have some issues with an erratic idle. Work I have done so far:

Replaced all ignition components (plugs, wires, cap, rotor, even coil).
Thorough cleaning of throttle body and IAC
New intake gasket
Replace vaccuum lines w/ silicon replacements
PCV replacement
New lower injector seals
Throttle position sensor appears correct

This work has steadied out her idle while in "drive" but she still has a hunting idle in "park" where the idle varies from like 500-1k in the worse case. Now that it is hot out, she is also having trouble compensating the idle for the AC compressor and e-fan when they kick in...this drops the idle to very low (about 500 on the tach) with the associated vibration. Is it possible that her IAC is going out? Any other major suspects I should investigate? Are there good tests for the IAC?

Thanks in advance!
Brian








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    Idle Issues on '94 940 Turbo 900

    posted by  someone claiming to be Robert on  Tue May 15 14:31 CST 2012 [RELATED]

    When my idle starts hunting up and down, I always go and check my MAP sensor vacuum hose line (regina system)and its usually the culprit. I would think on a Bosch it would be AMM. Unplug it, if no change in idle, its your problem. If idle changes its probably ok.

    I would then look at all the vacuum line connections, recheck intake gasket, all intake/throttle body vacuum connections, injector seals, IAC hosing, etc. Somewhere air is getting into the system ecu isnt seeing.







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