TPI Rev issues/Limp Mode?

[bdoobie69]

Hey all. I have been having issues with my car not being able to rev up. It will get up to about 3500 rpm and just hesitate like it is running out of gas. As soon as you let off the pedal the power kicks back in. My latest for investigating the problem was jumping across Pins A and B to throw the car into limp mode. When I do this it revs up just fine. Does anyone know what limp mode disables or any ideas on what I can look into?

[Z06vet]

Been a while since I had my 85 vette, but I had a problem simmilar to this & it ended up being the MAF sensor. Is it throwing any codes? Try disconnecting the MAF and see how it runs. This is just a wild guess without seeing/hearing more about the car. Let us know what happens. Scott

[bdoobie69]

I am actually running a speed density set up. The weird thing is that it is not throwing any codes at all.

[HILROD]

I worked on an 85 Trans am that was similar. The fuel pump was going bad. It had intermittent low fuel pressure. Also I've only seen one car that would run o.k. only when in diagnostic mode. It had a bad ECM. FRANK

[Dust87ss]

Hve you checked your TPS voltage to see that it is correct? Should be set as close to .54V as possible at idle and be over 4V at WOT. How does your O2 sensor look?

[bdoobie69]

I borrowed a scanner and checked a few things. I can't remember the exact readings, but the TPS as well as O2 seemed to look fine running down the road. Of course I just checked to make sure the readings were not all over the place. One thing I did find is that I was wrong initially saying that it ran fine in limp mode. I jumped across A and B and ran it after it was warm and had the same issue. I checked my fuel pressure and it was 52, so I may need that a little lower. I am also going to try another chip I have. Maybe Map sensor?

[MonzaRacer]

What system are you running? TPI GM I asume. also if so insert in a code key DOES NOT PUT YOU IN BACK UP FUEL. It puts the computer into a question mode and gives you codes as its programed to in flash codes from 12 on up and cycles.
So if it falls on its but above 3500 you need to look at several things, fuel preasure and volume. Is the Ignition causeing your problem or is it fuel.
first of all the number you look at on GM are block learn and fuel integrator, The system is trying to achieve 128 on both counts and will adjust up or down as fuel is added or subtracted.
Now if it is working properly then it should function up to about 5500 if I remember basic specs.
some things that can cause break up are inside the distributor, and actually the ingnition system.
fuel is another its real hard to diagnose a car online without seeing whats actually going on.
I am diag tech by trade so if you have any questions give me a shout.
Lee Abel
AFTERMARKET PERFORMANCE