95 STS fluctuating rpm and slight bogging while driving
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Northstar Engines and System Technical Discussion Discussion, 95 STS fluctuating rpm and slight bogging while driving in Cadillac Engine Technical Discussion; I have a 95 STS with the northstar. I just recently bought it and are fixing some of the problems. ...
  1. #1
    RRSTS is offline Cadillac Owners Member
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    95 STS fluctuating rpm and slight bogging while driving

    I have a 95 STS with the northstar. I just recently bought it and are fixing some of the problems. I have now ran across the motor bogging and fluctuating rpms while im driving it. It doesnt do it to much when I'm on city streets, but it does every time on the freeway. The rpm's will fluctuate no more than 300-400 and when i attempt to give it more gas to stop is when it bogs. it will stop for a little bit then happen again. I have changed out the plugs and wires to NGK platinum plugs and Bosch wires for the time being until I can get some GM plugs and wires. Could this problem be from not using the oem plug and wires or a bad ignition coil/coils? I would appreciate some insight so I can attempt to fix the problem to enjoy the Northstar. Thanks!



    Note: if it makes a difference i have replace the heater core, thermostat, water pump and all hoses. Also have thoroughly flushed the system.

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  3. #2
    Submariner409's Avatar
    Submariner409 is offline If it won't run, slap in a big stereo
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    Re: 95 STS fluctuating rpm and slight bogging while driving

    Parts at www.rockauto.com, www.gmotors.com, www.gmpartsdirect.com, or call Luke in Parts at Lindsay Cadillac, over there >>>>>>>>

    A bog sounds like vacuum or intake duct problems - go over the air filter and clamps/piping to look for a possible vacuum leak. Maybe read up in here and do a throttlebody cleaning. EGR, too.

    Was there any improvement with the new plugs/wires ??......or worse ???? Find vacuum leaks first. Read the sticky "How to pull codes" (top of main Northstar thread page) and find out if your car's built-in code reader/scanner is telling you something.

  4. #3
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 95 STS fluctuating rpm and slight bogging while driving

    A failing fuel pump is also a possibility. You'd have to hook up a fuel pressure gauge with a long hose and tape it to your windshield and watch the fuel pressure when this happens.

  5. #4
    RRSTS is offline Cadillac Owners Member
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    Re: 95 STS fluctuating rpm and slight bogging while driving

    [QUOTE=

    A bog sounds like vacuum or intake duct problems - go over the air filter and clamps/piping to look for a possible vacuum leak. Maybe read up in here and do a throttlebody cleaning. EGR, too.

    Was there any improvement with the new plugs/wires ??......or worse ???? Find vacuum leaks first. Read the sticky "How to pull codes" (top of main Northstar thread page) and find out if your car's built-in code reader/scanner is telling you something.[/QUOTE]

    I did put a aem dry flow cone filter on so i will change that back to the stock airbox. I drove the car hm 6miles back and it seem to run fine until I was almost back and found out the heater core was no good. So I changed it and did a tune up as I do to every used car i buy. I started to drive it and thats when the bogging/spuddering and fluctuating rpms started. I did pull up 2 codes P019 and T033. I will need to find out what these codes are and are probaly related to my problems.

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    RRSTS is offline Cadillac Owners Member
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    Re: 95 STS fluctuating rpm and slight bogging while driving

    Quote Originally Posted by Ranger View Post
    A failing fuel pump is also a possibility. You'd have to hook up a fuel pressure gauge with a long hose and tape it to your windshield and watch the fuel pressure when this happens.
    I will try this, thank you

  7. #6
    RRSTS is offline Cadillac Owners Member
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    Re: 95 STS fluctuating rpm and slight bogging while driving

    I found out that P019- shorted fuel pump circuit. Should i be looking for a short to one of the wires coming from the fuel pump? Or does this mean I need a new fuel pump?

  8. #7
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 95 STS fluctuating rpm and slight bogging while driving

    Can't tell without an inspection. Possibly a loose connector?

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