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Thread: stumble right off idle(89 lancer shelby)

  1. #1
    Mitsu booster
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    stumble right off idle(89 lancer shelby)

    no codes but it has a stumble right off idle. it sit for a long time and I had to replace the fuel pump. it seems to hit a brick wall when it goes into boost also.. any help will be appreciated.

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    Supporting Member II Turbo Mopar Contributor ajakeski's Avatar
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    Re: stumble right off idle(89 lancer shelby)

    It could be that additional fuel system components need attention. If the fuel filter is old , it should be changed. Check the injectors and rubber fuel lines.

    Look in the distributor and see if the shutter wheel is loose. This would cause erratic spark and fuel signals to be sent to the computer.

  3. #3
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    Re: stumble right off idle(89 lancer shelby)

    I haven't changed the fuel filter yet so that might be the problem.. another question, will the speedometer not working cause any problems?

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    Supporting Member II Turbo Mopar Contributor ajakeski's Avatar
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    Re: stumble right off idle(89 lancer shelby)

    Quote Originally Posted by v62go View Post
    I haven't changed the fuel filter yet so that might be the problem.. another question, will the speedometer not working cause any problems?
    It shouldn't but it could be a sign that the Vehicle Speed Sensor (VSS) is bad. Having a bad VSS could cause the car to stall when coming to a stop.

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    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: stumble right off idle(89 lancer shelby)

    Did you drive/own it before the long sitting period?

    Falling on it's face in boost could be a lean condition. Do you have any kind of AFR monitoring like a wideband?

    Dont push the red button.You hear me?

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    Supporting Member Turbo Mopar Contributor zin's Avatar
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    Re: stumble right off idle(89 lancer shelby)

    Get a scan tool on it if you can. The boost thing sounds like the MAP sensor could be bad and sending an "overboost" voltage... something that won't easily throw a code, but will cause problems (ask me how I know!). Also, temporarily install a fuel pressure gauge where you can see it while you drive, just duct tape it to the windshield if you have to, so you can see if the fuel pressure is what is causing the problem(s).

    Is the stumble there all the time off-idle, or just when it's cold?

    Do fix the VSS as I have heard of some weird problems that "fix themselves" when the VSS is working correctly, though it really shouldn't be able to cause the problems you're describing, it's just an easy fix that might save some more trouble down the road... and who doesn't like a working speedo anyway, right?

    Between the scan tool and fuel pressure gauge, you should be able to figure it out pretty quick.

    Mike
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    Re: stumble right off idle(89 lancer shelby)

    check the cam timing too. My 87 Shelby Lancer would fall on it's face leaving the line, I got beat by a nissan cube. Cam timing was retarded a tooth.
    Last edited by GLHNSLHT2; 05-11-2015 at 06:39 PM.

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    Re: stumble right off idle(89 lancer shelby)

    Its bone stock and has been sitting for 20yrs. Im going to change the fuel filter next . Anybody have a picture and the location of the vss? Thanks for all the replies and help.

  9. #9
    boostaholic
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    Re: stumble right off idle(89 lancer shelby)

    No good way to take a picture of the vss. Best to remove the airbox and it's sort of under the turbo on top of the trans. Held in with 1 10mm bolt if I recall on the passenger side. I take these out the top but perhaps it's easier out the bottom but I dont think so. Its a bear to get to and is likely well stuck in there after that amount of time sitting. They can be had on ebay nos pretty cheap. I think in fact I just picked one up for about $25.

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    Re: stumble right off idle(89 lancer shelby)

    the speedo is working now but I noticed it will boost fine cold but when the engine gets warm it acts up under boost.. any ideas??

  11. #11
    boostaholic
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    Re: stumble right off idle(89 lancer shelby)

    With no codes that's a tough one. Could be coolant temperature sensor, air temp sensor, collapsing vacuum lines due to heat, lean condition....

  12. #12
    turbo addict
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    Re: stumble right off idle(89 lancer shelby)

    pull vac line off fuel pressure regulator and see if gas comes out of it

  13. #13
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    Re: stumble right off idle(89 lancer shelby)

    It boost great when its cold but soon as it gets any heat on the motor it starts acting up when I run it up into boost.

  14. #14
    Supporting Member Turbo Mopar Contributor zin's Avatar
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    Re: stumble right off idle(89 lancer shelby)

    If the MAP is off (reading higher than it is), it will add extra fuel, when an engine is cold, it will like/tolerate more fuel, but not when it's fully warmed up...

    Have you confirmed you have an accurate MAP?

    Mike
    "The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government - lest it come to dominate our lives and interests." - Patrick Henry

    Bad laws are the worst sort of tyranny.
    - Edmund Burke

  15. #15
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    Re: stumble right off idle(89 lancer shelby)

    I also like to make sure to tee my map and fuel pressure together to the vacuum source

  16. #16
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    Re: stumble right off idle(89 lancer shelby)

    Replace all vac lines, fuel filter, new VSS, new MAP, new TPS, new plugs, wires, check FPR for gas, check for the cat being clogged...mice in the exhaust, lol...cam timing, etc. I had a car that ran like crap in boost when: spark plug wires were arcing, plugs were gapped too much, TPS was bad, MAP line had a leak, FPR diaphragm was ruptured.

  17. #17
    boostaholic
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    Re: stumble right off idle(89 lancer shelby)

    Compression and leak down numbers?

  18. #18
    turbo addict Turbo Mopar Contributor
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    Re: stumble right off idle(89 lancer shelby)

    VSS is an extra problem but not your main problem. Lack of VSS messes up decel, coasting, and idle coming to a stop.

    Its probably lean misfiring as Vigo said above.
    Brent GREAT DEPRESSION RACING 1992 Duster 3.0T The Junkyard - MS II, OEM 10:1 -[I] Old - 11.5@125 22psi $90 [U]Stock[/U] 3.0 Junk Motor - 1 bar MAP [/I] 1994 Spirit 3.0T - 11.5@120 20 psi - Daily :eyebrows: Holset He351 -FT600 - 393whp 457ft/lb @18psi 1994 Spirit 3.0T a670 - He341, stock fuel, BEGI. Wife's into kid's project. 1990 Lebaron Coupe 2.2 TI/II non IC, a413 1990 Spirit 3.0 E.S. 41TE -- 1993 Spirit 3.0 E.S. 41TE -- 1994 Duster 3.0 A543 1981 Starlet KP61 Potential driver -- 1981 Starlet KP61 Parts -- 1983 Starlet KP61 Drag 2005 Durango Hemi Limited -- 1998 Dodge 12v 47re. AFC mods, No plate, Mack plug, Boost elbow -- 2011 Dodge 6.7 G56

  19. #19
    Mitsu booster
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    Re: stumble right off idle(89 lancer shelby)

    it finally thru a code(check engine light)now it will rev to about 2500 rpms and acts like it hits a 2step... is there a easy way to check codes on these cars?

  20. #20
    turbo addict
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    Re: stumble right off idle(89 lancer shelby)

    Yep, read this page http://minimopar.net/fault/index.html

    You're in limp-in mode.

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