1990 chevy corsica 3.1v6 MFI 99k miles jerking at 38-40 mph?

i just bought this car a week ago, i gotten a very good deal on it but of course i had my share of problems with it but nothing i cant handle. But now ive done everything to this car and im trying to figure out why it jerks while driveing at 38-40 mph. here is everything ive done to the car so far- new throttle position sensor, fuel filter, pcv valve, air filter, oil change with oil filter, new spark plugs, new thermostat, cleaned the IAC valve, coolant flush, added sea foam to fuel, new spark plug wires, replaced air intank tube ( was tore up) and i think that concludes it. but now i still cannot find why it jerks at those speeds , it has no problem at anyother speed. ive even check the trans fluid and it was to the full line and it looks and smells fine. ive went and double checked my work and it good. still connot find what would cause this problem. anybody have any advise for me?

Update:

and when i say it jerks i mean it feels like theres a motor mount out ( but there isnt, there new according to last owner) i did a visual inspection and they do look new. and when it jerks i can feel the jerking slightly in the gas pedal and if i let off then back on the jerking stops or if i push down on the gas a little more it stops also. to me it also could be that the transmission is shifting up then back down or something but chevy made it hard for me when they decided not to put a RPM guage in this years model ( which sucks) so i gotta feel the shift.

3 Answers

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  • Anonymous
    8 years ago
    Best Answer

    fuel pump might do it have it check for correct fuel pressue also chech your ox. sensors as it seams you have replaced every thing except the mfi and the ox sensors as wellas crank postion sensor

  • yousef
    Lv 4
    3 years ago

    ok, hi, properly to start up, is the examine engine mild on?,have been there any present day upkeep? this would sound like properly that's a team of issues, that's a gasoline pump, having low stress, it must be possibly cluth band interior the trans slipping, that's a limited exhaust , or a throttle place sensor, or possibly a map sensor, the egr valve could do it additionally , if it replace into getting caught over lower back, and as for the pcv valve is placed the two the rear valve cover , or under the intake mmanifold.

  • Sagery
    Lv 4
    8 years ago

    Sounds like the steel belts in your tire(s) have cut lose and have balled up to one part of the tire(s).

    Get new tires.

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