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P098 ........................................... High RPM P/N to D/R Shift Under ISC

This code came up on my Cadi. Anyone have any insight as to what causes it and how to fix it? My car has been downshift at high RPM's for the past few months, but I haven't noticed it getting any worse.

Actually, it's E98 or E098 on my 90 Deville...
 

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Snyder81 said:
P098 ........................................... High RPM P/N to D/R Shift Under ISC

This code came up on my Cadi. Anyone have any insight as to what causes it and how to fix it? My car has been downshift at high RPM's for the past few months, but I haven't noticed it getting any worse.

Actually, it's E98 or E098 on my 90 Deville...
I have the same error code on my 92 eldo. I have no clue what it means or how to fix it. Same problems your having tooo. Picking up a manual today at 5 if i can fix it this weekend i will post. Anyone else have any ideas. I also got Ao11
 

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I posted an answer to SOMEONE that had this issue recently. What you should be looking for is a vacuum leak, mis-adjusted TPS, mis-adjusted ISC, etc. Hell, even a binding throttle cable can cause this problem. Anything that causes the idle to be abnormally high.
 

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Katshot said:
I posted an answer to SOMEONE that had this issue recently. What you should be looking for is a vacuum leak, mis-adjusted TPS, mis-adjusted ISC, etc. Hell, even a binding throttle cable can cause this problem. Anything that causes the idle to be abnormally high.
Kevin it was me i think.

I have checked for a vacuum leak, and the throttle cable.
problem when away now its back.

what is a mis-adjusted TPS and a mis-adjusted ISC.
sorry man you got to dumb it down.
 

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JJhomer83 said:
Kevin it was me i think.

I have checked for a vacuum leak, and the throttle cable.
problem when away now its back.

what is a mis-adjusted TPS and a mis-adjusted ISC.
sorry man you got to dumb it down.
Throttle positioning sensor
and idle speed control.
They could be the cause for many shifting problems and fast idles. The tps is not as easy to install as other sensors because it needs to be adjusted, as opposed to the usual plug 'n play. I have the same problem.
 

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ok I own a beautiful 89 fleetwood with 130k:coolgleam. The engine was trying to leave me behind it would have the rpms going up and down constantly revin if i were on a stop light it would seem as if I were going to race lol it moves the car. A buddy of mine told me it was the ISC so I disconnected it drove like that for a week but noticed that at a red light it would turn off. so I headed to Autozone bought a new ISC and put it in my self...problem fixed...:rant2: NO!! now it doesnt turn off but it still wants to leave me behind its gonna blow the engine and i get horrible mileage because of this (9.5-12 Av.mpg) What do I do? :banghead:
 

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I took my 89 DeVille to a Chevy dealership and they got some completely unknown code. Probably this one, since it deals with the idle. They had to call Cadillac to find out what it was. They did something and it does it LESS now. It's not anywhere near gone though. Very annoying problem. I'm sick of spending so much cash on the car and it still doesn't work right. Almost two g's in just labor and parts. Two g's for the car. Four g's for a semi-working DeVille!! Woo-Hoo!!
 

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When the ignition is turned off, the ISC will set up for the next start. It should not ratchet.

Open the throttle slightly and depress the closed idle switch. The ISC plunger should retract. RPM should drop to about 450 and the engine may stall. When the ISC plunger is fully retracted, disconnect the electrical plug from the ISC motor. Now release the plunger. There should be about .060 clearance between the throttle lever and the isc motor plunger when the plunger is fully retracted and the throttle is at rest. If not, adjust the plunger to obtain .060" clearance.
 

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There is an idle learn proceedure but my understanding is that it will "learn" by just driving it.
 
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