90 Jetta

Just bought the car and ran good on test drive (engine hot). When cold it will start normally but within 30 seconds it begins stumbling and won't accelerate. If you can keep it running until hot it seems to run normally extept it will occassionally stall when comming to a stop. Replaced ect sensor, no help. Fuel pressure at 40 psi when just starting cold and begins to raise to 45-50psi just after engine starts to stumle. Previous owner changed engines from a PF (serial #) to an RV about 30,000 miles ago. It has a 5 sp trans and all of the grounds seem to be intact. Can Anyone help?

SOunds like bad maf sensor.

SOunds like bad maf sensor.


Thanks for the help. I haven't had time to check it out yet. Waiting for the service manual to arrive. I replaced the ect sensor because it sounded temp related.

Hey,
Received Bentley manual today and checked out the MAF per instructions and it seems ok. Question I have is, when checking resistance between pins 2 &3 at the MAF is supposed to "vary" as the flapper is moved. Should it gradually increase in resistance as a TPS would. This one does not. It will increase to a point and then begin to decrease.
Thanks for the help.

SHould increase/decrease just like tps (same kind of potentiometer)

I believe there is an update for this.. its the cold start relay i think, i would have to look. It involves adding a relay to the harness.