Help! Unable to rev past 5000

[WVZR-1]

Is this a car with headers? If this is a car with headers and it was thought to maybe be a secondary injector issue couldn't you just use a pyrometer and check cylinder temps? Just asking. Sort the cylinders to those controlled by each injector module.

Pete - a swap of PROM would substantiate the possible issue there?

Chris - you do have another?

[chriskinzel]

Replaced the crank sensor, and the fuel filter. I also reseated the PROM. Went for a drive and it still stalls out at 5000. I pulled over in a parking lot and while in neutral slowly reved it. Sometimes it would stop at 5000, other times I could get it to 7200. If it went past 5000 it would keep going to the end. If it stopped at 5000 the tach would only bounce about 100 rpm, just about what the engine is running. I am now totally confused. I don't have headers, secondaries removed, with Marc's chip the ECM is open the the atmosphere, no vaccume pump anymore. I am stumped!! Fuel Preasure is still good.

Chris:

[Pete]

Does it shut down at 3k or5k
3 would be secondaries 5k sounds
like ignition module.
I meant make sure the electrical plugs are
plugged in.
Changing to stock chip will not help since he has removed secondaries.
When did this start what was the last change to car.

Pete

[chriskinzel]

Originally Posted by Pete

Does it shut down at 3k or5k
3 would be secondaries 5k sounds
like ignition module.
I meant make sure the electrical plugs are
plugged in.
Changing to stock chip will not help since he has removed secondaries.
When did this start what was the last change to car.

Pete

It ran good up to 5k this time. I didn't drive it far, so it didn't get really hot. It has been this way all summer. It seems to have happened after I removed secondaries. All plugs are in tight, even rechecked plug tightness and wires. Really frustrating. Anyone have a known good ignition module they would lend, or rent me? The permagrin is fading.

Chris

[QB93Z]

To me, it sounds like the problems I have seen in cars that still have the secondaries installed and the secondary vacuum system is not tight. The ECM shuts down the secondaries and turns off the secondary injectors and you see a code (which I don't remember the number but it references something like secondary vacuum low)

So in your case, with the secondaries removed, the ECM still has to get an input from the Secondary Vacuum Pressure Switch. Is the pressure switch connected it's normal wiring connector. If not, the ECM may not be turning on the secondary injectors.

Good luck with your trouble shooting!

Jim

[chriskinzel]

Originally Posted by QB93Z

To me, it sounds like the problems I have seen in cars that still have the secondaries installed and the secondary vacuum system is not tight. The ECM shuts down the secondaries and turns off the secondary injectors and you see a code (which I don't remember the number but it references something like secondary vacuum low)

So in your case, with the secondaries removed, the ECM still has to get an input from the Secondary Vacuum Pressure Switch. Is the pressure switch connected it's normal wiring connector. If not, the ECM may not be turning on the secondary injectors.

Good luck with your trouble shooting!

Jim

Where is the Secondary Vacuum Pressure Switch located? What does it look like?

Chris

[QB93Z]

The pressure switch looks like the MAP sensor (without the sheet metal cover).

On a 1990 it is under the ECM, and a vacuum line from the operator side of the Secondary Actuator Solenoid Valve, comes from under the plenum and runs to the Vacuum Switch.

On 1993 and up, the Vacuum Switch is fastened to the under side of the Plenum, forward of the Ignition Module.

For 1991, I don't remember the location. Sorry.

I believe that the ECM requires the Vacuum Switch to be plugged in but a "Secondaries Removed" chip changes the set point to atmospheric.

Jim

[chriskinzel]

I think that I removed it when I pulled the secondaries. The ECM is now atmospheric. Thanks anyway....keep thinking.

Chris

[QB93Z]

Originally Posted by chriskinzel

I think that I removed it when I pulled the secondaries. The ECM is now atmospheric. Thanks anyway....keep thinking.

Chris

The Pressure Switch needs to be installed for the ECM to energize the 2nd injectors.

Jim

[chriskinzel]

Originally Posted by QB93Z

The Pressure Switch needs to be installed for the ECM to energize the 2nd injectors.

Jim

According to the FSM, if there is too much, or too little vacuum there should be an error code. No codes. I may, or may not have this switch. I will keep looking for it. I do have a wire connection ( 2 wires with a white connector) that is not hooked up under my plenum. It is towards the front. Not sure where this goes, but I rember unplugging it when removing the secondaries. Problem?

Chris