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Discussion Starter #1
I read some of the posts but it's not quite clear to me. I've cleaned throttle body and I retract the ISCP plunger the engine's running at about 550prms or so. But after a few minutes(car is warm 95 degrees C) the car begins to surge and then finally cuts off. Once at this point it will only run for about a min, surging most of the time. Should the car be able to run for longer than this??? Should it not surge??? If not any ideas wat could be causing it??? Yall think it could be EGR related??


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bharner said:
I read some of the posts but it's not quite clear to me. I've cleaned throttle body and I retract the ISCP plunger the engine's running at about 550prms or so. But after a few minutes(car is warm 95 degrees C) the car begins to surge and then finally cuts off. Once at this point it will only run for about a min, surging most of the time. Should the car be able to run for longer than this??? Should it not surge??? If not any ideas wat could be causing it??? Yall think it could be EGR related??


Thanks
You should have done all your adjustments when engine is at operational temperature (around 195 F). The ECM drives the RPMs down as engine's temperature increases. If the adjustments were made below operational temperature, the ECM will drop the RPM too low and engine will eventually stall.
 

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Discussion Starter #3
thanks for the reply. this happens with out making any adjustments. i never got to make adjustments cuz it cuts off everytime it gets above op temp. i am only trying to get TPS and min air reading.(testing). So the car will not run very long at min rpms if its working correctly?


oh and its a 92 deville
 

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Ok, when you start the car in the morning what are the RPM in 30 seconds aftrer starting? Do you get any codes. It is a good idea to keep posting within the same thread so others would get all possible info.
 

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Discussion Starter #7
Min RPM at 55 deg C is around 550-600. So your sayin that is too low. Also are you saying that the engine will cut off once it gets warm running at min rpms(isc plunger full retracted)???
 

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bharner said:
Min RPM at 55 deg C is around 550-600. So your sayin that is too low. Also are you saying that the engine will cut off once it gets warm running at min rpms(isc plunger full retracted)???
I am a little bit confused....Mine idles at 575-600 only when engine is wormed up by driving for some 10-15 minutes... No, engine should not stall when it worms up. The higher the temps. the lower RPM engine can take without stalling. Search the archives for "stall" "cutting off" etc. I remember posts describing exactly the same situation. It may be something not related to TPS, ISC motor. The ECM makes decisions based on th einput from several sensors.

Does your engine (@ 195 F) stall when you retruct the ISC plunger completely and let the throttle lever rest on the minimum air screw? Did you clean the BACKSIDES od the throttle blades and the EGR tubes as well?
 

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Discussion Starter #9
When the engine is warm and ISC plunger fully retracted and throttle lever is resting on min air screw it will run about 5 mins at 525 rpms but then it will begin to surge(500 to 600 rpms) maybe for a min then cut off. After that if I restart her while engine is warm she will just surge and cutt off. At min air (525 or so rpms) it should stay running. It should not surger or cut off correct???

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When the ISC plunger is retracted completely the first thing to check is that there is a gap from the plunger to the throttle lever so that the throttle lever is sitting on the min air stop.

Check min air with the engine thoroughly warmed up and try entering fixed spark mode before checking the min air to minimize any RPM surging. You should also have the AC off when checking min air.

The engine should idle down to 450-500 at min air with the AC off and engine hot. There should be about .030 inch gap between the ISC plunger and the throttle lever.

Make sure the cruise control link is not holding the throttle open at min air making the idle too high. Remove the cruise control link , retract the ISC motor plunger and check the min air. Reattach the cruise link while the throttle body is at the min air setting and idling at 450-500. Attach it so that the link is just barely taute but still with a tiny bit of free play. IF in doubt go to the next loosest adjuster hole for the link.
 
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