1991 Seville 4.9L Engine Stumble (TECH PLEASE) - Page 2
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HT4100 4.1, 4.5, 4.9 Discussion, 1991 Seville 4.9L Engine Stumble (TECH PLEASE) in Cadillac Engine Technical Discussion; Originally Posted by cjhudson87 Can anybody tell me what the TPS angle values should be with my car RUNNING at ...
  1. #16
    ehall's Avatar
    ehall is offline Cadillac Owners Connoisseur
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    Re: 1991 Seville 4.9L Engine Stumble (TECH PLEASE)

    Quote Originally Posted by cjhudson87 View Post
    Can anybody tell me what the TPS angle values should be with my car RUNNING at idle?

    I am seeing 0.2...I thought I saw somewhere where it said it should be 3-4.
    I see 0* at cold idle parked, 2* at warm cruising (foot off the gas but not stopped), and 0* at warm stop. The only time I see 4* is cold cruising.

  2. #17
    awadecki is offline Cadillac Owners Enthusiast
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    Re: 1991 Seville 4.9L Engine Stumble (TECH PLEASE)

    OK, on warm coastdown, it should always read 2.1-2.5. The computer is programmed to this setting irrespective of how high this idle speed is. At idle in drive, your reading should be around 1-1.5. At idle it park, it's probably around 0.5 or so.

    Check your EGR. It's probably the issue.

  3. #18
    ehall's Avatar
    ehall is offline Cadillac Owners Connoisseur
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    Re: 1991 Seville 4.9L Engine Stumble (TECH PLEASE)

    Having re-read the thread, problems #2 and #3 are a result of the EGR being open when it should not be open. The computer reads a variety of inputs (speed, throttle position, coolant temperature, etc) and then tells the EGR solenoid to open and close the EGR valve. The problem with your stumble on light acceleration is that the EGR is open when it should not be open--this could be because the valve is stuck, or the solenoid is broken, or because one of the monitoring systems (such as the TPS) is sending a bad signal.

    Giving the #1 problem you describe I would guess that the valve is stuck open. It's possible that the solenoid is fried and is releasing constant vacuum. The only way to determine this is to put a vacuum gauge on the line between the solenoid and the valve and see if the solenoid turns on and off. Personally I would just clean or replace the valve first.

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