E55, E98 codes on 93 Deville - Page 2
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, E55, E98 codes on 93 Deville in Past Cadillac Vehicle Discussion; Did you ADJUST the ISC motor?...
  1. #16
    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
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    Did you ADJUST the ISC motor?

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    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: E55, E98 codes on 93 Deville

    If the ISC is retracted it should not be contacting the throttle arm. The car should not be idling too high with the ISC not touching it. If it is, then something else is wrong, vacuum leak or min idle incorrect. It's usually just the adjustment though.

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    nashcaddy is offline Cadillac Owners Fanatic
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    Re: E55, E98 codes on 93 Deville

    I thought the ISC does come in contact with the throttle? ON all the caddy's I've seen at pull a part the idle is touching the throttle. Mine always has. I did adjust the ISC and it seems I may have ruined it because now it's ratcheting everytime I turn the key and when I turn the car off. Idle is still high after I adjusted it but I did not adjust to where it was not touching the throttle. So could it have been misadjusted all this time then? I have read the posts where they say it should be a slight amount of space between the ISC and throttle but mine seems to have been fine....I guess not. but I still don't know what I could have done that started this in the first place. I know I jostled that big bunch of wires near plugs 2 and 4 when I was trying to get the boots off and change the plugs. I know those wires and bundled with the MAP sensor wires and TPS wires.

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    Re: E55, E98 codes on 93 Deville

    someone help me here...i'm still getting E55 and E98 codes after I changed the ISC motor. I did unplug the TPS cable and it gave me a code so I know those wires are intact. Does this mean I need to change the TPS?

  5. #20
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: E55, E98 codes on 93 Deville

    It does sound like there is an issue with the TPS. I never play around with them much because I seem to have bad luck with them. I guess you will have to go through the procedure to adjust it and hope it works, if not it may be defective. I had one on my Buick that I could not get adjusted right so I ended up buying a complete throttle body from a wrecked car and put the whole thing on as is.

    The ISC will always be contacting the throttle arm except when unplugged and retracted for adjustment. When the car is shut off it will be holding the idle where it needs to be to start the car. That's why the ones in the junkyard are still in contact with the throttle arm. That's why I mentioned the unplugging test to rule it out in your high idle issue. If it is unplugged and retracted with a normal gap the car should not be idling too high. If it is, then it isn't the ISC. The high idle will give you the code 98, probably a misadjusted TPS will too. That's why it is easiest to rule out the ISC first. If you ever have time to read all the ISC threads here, you will understand it frontwards and backwards after a while.

  6. #21
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    Re: E55, E98 codes on 93 Deville

    Quote Originally Posted by cadillac_al View Post
    I
    The ISC will always be contacting the throttle arm except when unplugged and retracted for adjustment. When the car is shut off it will be holding the idle where it needs to be to start the car.
    Doesn't the ISC motor retract the plunger at key off to completely close off the throttle plate and thus prevent dieseling? I always thought it extends and comes back to idle position to start the car at key on.

  7. #22
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    Re: E55, E98 codes on 93 Deville

    I'm sure it retracts some to prevent dieseling. If it retracted all the way with the key off, that would make it too easy to do adjustments and you wouldn't have to go through the revving and unplugging procedure to retract it. Mine always made a few noises after the engine was shut off. Some people say that is a sign of trouble but mine always worked perfectly. I think the noises it makes after key off is getting ready for the next start. It would make just as much sense to do this at key on but who knows (the FSM knows). In any event it's not hard to adjust it correctly or rule out a defective one.

  8. #23
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    Re: E55, E98 codes on 93 Deville

    I'm going to try to change the TPS. I tried to get at it last week but couldn't reach the far screw. I've changed it before but don't know why I was having so much trouble this time. There's a bolt kind of in the way from another part that I can't think of right now....what is that...egr valve? I gotta figure out how to get on of the screws out of it.

  9. #24
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    Re: E55, E98 codes on 93 Deville

    Ok, so I was able to change the TPS. The ISC is till ratcheting like crazy when I turn the key on and turn the car off after driving. I have absolutely no codes though. Not even the dreaded E39 code that has always shown up since I bought the car 4 yrs ago. I guess I will swap out the ISC motor and see what happens. I almost want to leave it the way it is.

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    Re: E55, E98 codes on 93 Deville

    If the ISC motor is simply ratcheting at key on and key off I suspect it is adjusting itself. I remember my '92 doing that at key off. If it is not affecting idle and you have no codes, leave it be.

  11. #26
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    Re: E55, E98 codes on 93 Deville

    If the system is properly calibrated, all that should happen after shut down is the plunger extending to a position in preparation for next startup, as determined by the PCM. One :zzzzzip: is all you should hear.

  12. #27
    nashcaddy is offline Cadillac Owners Fanatic
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    Re: E55, E98 codes on 93 Deville

    It's running better but the idle is still a little off. I think at times the plunger is retracted too much and at times it seems the idle is a little high but not much. Sometimes when I am in a parking lot and not giving the car gas as I'm about to make a turn or turn into a parking space it almost shuts off....I'll adjust it and see what happens. Some days I don't have enough time to play with it which is why I can't respond as quickly. Thanks for the replies.

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