1992 Chevy Cavalier

TYRAL

MEMBER
1992 CHEVROLET CAVALIER
6 CYL
FWD
MANUAL
315,000 MILES

My Cavalier RS 3.1L V6 shakes VIOLENTLY when I lift the clutch from a standstill and when I am driving. It idles well since I replaced the idle air control valve. It has regularly given me code 34 (map sensor- junk yard) which I have replaced a couple of different times with no success. It runs ok when it is cold but after it heats up, it shakes and dies when the clutch is lifted. If I rev the engine very high and ride the clutch slowly letting it up, it will go but then when I shift into second it does it again. I thought that it might be a vacuum leak somewhere but there seems to be good suction when I loosen the line on the map sensor, and I can't hear any hissing. Also of a side note the heating system won't select any different vents it just comes out of all of them lightly. And the speedometer has hit maximum when I was reving the engine, but not moving. I have been struggling with this for a long time and any help is appreciated.
thanks

Dave
PS 315000KM not miles

1 Reply

MMPRINCE4000

MECHANIC
8,548 POSTS

The MAP sensor is critical to the engine management. If you are getting a MAP sensor error, replace it and check the vacuum hose for obstruction.

When the MAP is out of normal range, the ECM will set a default value, this will be a rich value to prevent a lean condition. The value is WOT (wide open throttle), so it is pumping a lot of gas in the engine and will eventually destroy the O2, CAT and may get into oil and cause bearing damage.
In fact the CAT is probably already clogged, further causing performance issues.