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Discussion Starter #1
I knew '92 4.9 ISC was going....let it sit for 15-20min start it and up...down...up..down...almost die then idle fine, otherwise start cold or start back up right away ran fine and idled right. Now it does not want to even start without holding the pedal to can idle speed you want. Idle screw is not set right or the timing is retarded...should idle at 500-550rpm even without ISC working right ? Common problem I guess from this board that I've seen, mine went 118,000 befor going south. This afternoon I have a new GM ISC to put in....according to the hayes book you:
Take the old out.
1.Start the car, warm it up.
2.Set the idle screw(located on the throttle body) to 500 to 550 rpm.using a "good"tach hooked up to the distributor.
3.Put it in the timing mode...set the timing 10 deg btdc @ 500 to 550rpm (re-adjust idle screw after timing if needed to 500 to 550rpm)
Jumper the new ISC to retract the plunger all the way in.
Mount the new ISC plunger fully retacted, set the plunger to .030 clearance between the throttle blade and the ISC plunger.
4. Unhook neg cable and do the idle learn process..15min climate control off...5min in drive climate control off...5min auto climate control(full cold setting to run the compressor) on....then chop the ignition....
Done...smoooooth idling Caddy right? did I miss anything?
Let me know Thanks!
 

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Sounds about right but as I recall (probably in the archives), simply press on the plunger til it retracts and then unplug it (engine idling). It should drop to about 450 RPM (maybe stall). Then set the plunger to .030. Now reinstall the connector. No need for a tach or timing as I recall. You can perform the idle learn or let it learn as you drive it.
 

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Discussion Starter #3
Ranger, it looks like the GM ISC part already comes retracted. I'm going to time it anyway just see where it's at. Done everything else might as well time too.
 

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Discussion Starter #4
Repaced it. didn't get a good learn idle process...had to quit in the middle. Next day I decided to run the codes before I did a learn idle. No current codes, a e30, and e33 history code came up...then it said ecm? I tryed to clear the codes hit the high fan sw...and it came up pcm?....hit it again icm? The way the book says...you run though this til you get Clear code...then clear it? HELP...shead some light on this for me??? I did do a re-learn by un-hooking the neg...it seams to run the way it's suppose to...it has not idled up and down almost killing at warm start the way it did...maybe it's fixed we'll see...
 

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I forget exactly how the '92 diagnostics work, but basically when promted with PCM?, answer yes (I think HI FAN is yes and LOW FAN is no.) You are now in the PCM mode. Answer no to "peramiters", "data" and "overrides" til you see "clear PCM codes?", then answer yes. Having said that, you probably cleared the codes when you pulled battery power.
 

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Discussion Starter #6
Thanks Ranger, I think it clears the codes and resets the ecm when you remove power. We'll see how it restarts warm, if it goes up to 1500 then almost dies, then up again..then down again I'll pull my hair out and give up cause it starts perfect cold.
 
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