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Thread: Poor prformance under all conditions and TERRIBLE gas milage

  1. #1
    Join Date
    Jul 2004
    Winnipeg, Manitoba

    Poor prformance under all conditions and TERRIBLE gas milage

    wow i never really though about it but my car gets AWEFUL milage and its always seams likes its missing

    i only get 180-190 miles outa a tank of gas on the bes weeks i get 200.. this is driving like a grandpa.. what could casue this . mny best gues is leaking headgaskets getting bad

  2. #2
    Join Date
    May 2003
    Robinson, Pennsylvania
    if its missing check plugs and wires first and try some stp gas treatment , if you think its a headgasket does it use much coolant? one time mine had no power but didnt miss wouldnt even go uphill after a couple days it was a bad harmonic balancer

  3. #3
    Join Date
    Aug 2002
    Valley Lee, MD

    I may be fixing your problem now

    My 94 has been doing the same thing yours is doing for about a year. Idles rough, 11 MPG and loss of power but it runs decent on the road. I exhausted all possibilities and spent a lot of money before I finally did a compression check. WOW was I surprised! What I found was I had only 2 good cylinders. I could not believe the car even run. I naturally, as you did, thought it was HGs. So I pulled the heads off to find the HGs were OK. WOW surprised again! No breaks or cracks in the HGs or the heads and no broken head bolts. I even pulled and tugged on the HGs to see if I missed something. That made me scratch my head real hard but it made sense since I was not puking antifreeze or overheating. Been there, done that! However, that did not explain why the compression was low. So I took the heads to get them resurfaced and pressure checked. My machinist told me that I had 4 burnt exhaust valves and they were surprise surprise the 4 cylinders that had little or no compression. THe other 2 exhaust valves were on there way out. My point is do a compression test early to save yourself a lot of time and money. I wish I had!

    Ed Springer

    90 Black XR7 5-speed: 70mm TB, Fresh Air Intake, '94 Supercharger, 5% SC Pulley, Raised SC Top, I/C Fan, UD Pulleys, 190 l/h Fuel Pump, 36 lbs Injectors, Headers, Magnaflow Muffler (no cats) with stock resonators, 3:27 Gears, Ripper Shifter, 73mm CL MAF (Blue Tube), Magnacore Wires, NGK Iridium Plugs, Royal Purple Lubricants and Rear Spring Air Bags.

    94 Red SC Auto: 70mm TB, Fresh Air Intake, Stock 90 SC Pulley, Raised SC Top, I/C Fan, 190 l/h Fuel Pump, Headers, Raven Muffler (no cats) with stock resonators, 3:73 Gears, Accel 36# injectors, 76mm C&L MAF (Gold Tube), Magnacore Wires, NGK Iridium Plugs, MSD DIS-4 Ignition Box with Tach Adapters, Royal Purple Lubricants, TRANSGO Shift Kit, Pro-Torque 2500 Stall TC, Haydon Auxiliary Transmission Cooler, Tokico Struts & Shocks, American Racing 17 Sniper Wheels, Michelin Pilot Sport A/S Tires and 235 RWHP with 315 LB-FT Torque.

  4. #4
    Join Date
    Jan 2003
    Roswell, Georgia
    When my mileage dropped to 10mpg, it got my attention.
    (plugs had a huge gap, say .09 - .10)
    So I changed the plugs and wires, and it added 2 mpg.
    Then changed O2 sensor and that added 2.
    Then lost the original supercharger and that added 2 mpg.
    (tied the bypass valve open)
    I now got about 16.5 mpg in the city.
    Now with reman SC, I'm back down to 13-14 city driving.

    (as previously mentioned gas treatment/injector cleaner would help
    smooth it out a bit)

  5. #5
    Join Date
    Sep 2004
    Fort Saskatchewan,Alberta


    have you run diagnostic codes and if you did what were the codes ?? seems your car is in ""limp home" mode for some reason. the computer is increaseing fuel and backing off the timing. you need to do computer diagnostic first !!

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