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1993 Cadillac Coupe De Ville (113000)
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Discussion Starter #1
on my 1993 deville I have adjusted the ISC motor and the TPS to the specs but now it behaving badly on cold start the engine races to over 2000 rpm then drops down making me ask this question. when adjustiong the isc motor to .060 is the plunger depressed or fully extended? I know that the motor should be retracted all of the way. I adjusted my ISC motor with the motor shaft retracted and the plunger extended.
 

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2010 DTS
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The plunger should be retracted. Press on it and it should retract. When it bottoms out, pull the plug and adjust it to .030.
 

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1993 Cadillac Coupe De Ville (113000)
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Discussion Starter #3
OK so retract the ISC motor shaft and retract the plunger to 0.030.
 

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1991 Cadillac Fleetwood 60 Special
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230 Posts
No, Waht Ranger means is once the ISC motor is retracted and the wires disconnected, you measure the gap, without further pushing on the plunger: motor retracted and plunger (throttle switch) at rest/extended.

The reason your engine is racing at cold start is because you have to to do the idle learn after adjusting the TPS, because now when you start the car it's using the old TPS value thinking the throttle is closed more than it actually is. Hence the high revs at startup.

Once the idle learn is done, the car will rev a bit at startup (this to get oil pressure up fast), but not excessively.
 

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1993 Cadillac Coupe De Ville (113000)
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Discussion Starter #5
OK I did the procedure and the idle has returned to 630-680 on cold start (FL 85 F) the idle has returned to high idle for a moment then drops quickly to what seems normal. The engine spec says that I should be able to get it to 525-550. I suspect I have a small vacuum leak, I have no codes I have replaced all of the rubber that touches the TB. Any other ideas where to look, I am look for what are the usual areas/ obvious area that a leak could happen, most connections seem tight. Also I need a primer on finding leaks as it has been 20 years since I last looked for vacuum leaks.

Thanks for your help.
 

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'87 Coupe DeVille 4.1L FWD(New engine '08) 1981 F100 '03FXDL
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One old-trick is a short-shot of carb-cleaner at suspected leak point.....idle will rise for a sec or more. A MityVac hand vacuum pump kit is a handy tool to have for many tasks. Replacing every vacuum hose in the engine compartment is a good thing and cheap insurance....maybe $20 +/-
 

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1993 Cadillac Coupe De Ville (113000)
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79 Posts
Discussion Starter #8
Good one, the PVC grommet is a slip fit could me tighter, I have it to 600-650, I might turn in the ISC screw a bit more, not sure yet. just took it for a 4.5 mile jaunt, the roads here Tamarac, FL are about 45mph with lots of lights. got 22.2 as I shut her off, I reset the computer stuff and came up with that number. this is the best yet, yes I did sit a few lights. I replaced one more vacuum bit at the trans diaphragm. I will replace the pvc grommet and check other hoses with tb/carb cleaner at a later time.

thanks for the help

it always easier when you know how.
 

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1993 Cadillac Coupe De Ville (113000)
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Discussion Starter #9
Oh, one more thing, the parking brake won't hold down (ratchet) it just releases, I did redo the brakes and wheel cylinders. I checked for binding linkage and lubed it with wd-40, but still no luv. I listened for leaks and did not here any, the hose looks in good condition. I thought that would be something, the ratchet parking braked worked after I did the brakes for a week anyway. I am thinking leak, any ideas ?
 

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'87 Coupe DeVille 4.1L FWD(New engine '08) 1981 F100 '03FXDL
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behind the brake pedal there is a vacuum operated diaphragm that releases the PB. Maybe hose is disconnected.
 

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2010 DTS
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That's not the problem. If it where a vacuum leak it would not disengage. You either have constant vacuum, holding it in the release position or something mechanical hanging up. Pull the vacuum line and try it. If it holds, then you have to figure out why it is applying vacuum in the park position (it should not).
 

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'87 Coupe DeVille 4.1L FWD(New engine '08) 1981 F100 '03FXDL
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Apparently I can't read very well anymore. Park brake mechanism problem, not release problem. Maybe the release lever is stuck in the release position.
 

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1993 Cadillac Coupe De Ville (113000)
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Discussion Starter #15
I have checked the vacuum supply and there is vacuum when I put in grear. With the car off (no vacuum) the diaphragm linkage moves up and down freely, the pedal moves freely and the release lever moves freely. ?
 

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Then you just need to work it and study the operation until you figure out what is holding what in the release position. You should not and won't have vacuum with the engine off (you turned off the vacuum supply). Do you have vacuum to the diaphragm with the engine running in park? You should not have vacuum to the diaphragm in that mode.
 

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'87 Coupe DeVille 4.1L FWD(New engine '08) 1981 F100 '03FXDL
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If the front cable is attached to the cable capture/connector, does pushing the PB pedal actually apply the rear brakes? When the redo of the rears was done, maybe something has gone wrong inside the rear drums or in the cable system.

My car came from Miami. It is table-top flat down there, so folks don't use the park brake. Upon driving back to Texas I stopped for gas in Ocala. Naturally applied the PB. Upon leaving the release system 'popped', but the car didn't want to back-up. The rear drums were locked! Managed to free the cables in the drums and got back home. Took the drums off. Every piece/part was rusted to worthlessness from non-use. When I applied the PB the mechanism in the drums just locked up tight. Being able to free those cables without taking the drums off is possible, so maybe your cables did it to themselves somehow....
 

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1993 Cadillac Coupe De Ville (113000)
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Discussion Starter #18
yes the operate as they should, I drive down the road at an idle and make about 10 mph and press the pb and the car stops.
 

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1993 Cadillac Coupe De Ville (113000)
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Discussion Starter #19
ok I tested the vacuum, to test I removed the little pink hose from the parking brake actuator, started the car, drove through the house and yes I have vacuum in drive. the house bit was a joke. I can't see up aboe the PB assembly it all look connected and I have not changed any think under there. It my be in the back I will check with a friend he is an old school mechanic in Maine he is not here in FL.
 

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1991 Cadillac Fleetwood 60 Special
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OK I did the procedure and the idle has returned to 630-680 on cold start (FL 85 F) the idle has returned to high idle for a moment then drops quickly to what seems normal. The engine spec says that I should be able to get it to 525-550.
The 525-550 idle spec listed is with ISC fully retracted and throttle resting on minimum idle screw, not normal operating idle. Your idle seems fine. Turning the ISC plunger in or out will have NO impact on the idle. The computer decides what RPM at which to idle. You can't adjust it.
 
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