ZR1 Full Power Issue

[Paul Workman]

FYI, this is the vacuum circuit for the secondaries (see FSM). This diagram is from a 90, and the "SWITCH, DIFFERENTIAL PRESSURE" is attached under the ECM bracket. But, the switch is located UNDER the plenum on 91-95s.

NOTE: Normally, the vacuum reserve canister is charged by plenum vacuum when the engine runs. The vacuum pump & reservoir supplies vacuum to hold the secondaries open when vacuum drops at WOT.

However, if one chooses to delete the secondary vacuum system all together (as many have - running with the secondary throttle plates fixed open or removed entirely) you need not worry about any of that secondary headache and run on FULL ENGINE POWER 100% of the time (except at idle only).

[jss06c6]

Bryan,

I had a client car that was a bear to troubleshoot with same issues. Fuel pumps and secondary vacuum system were fine. There are two secondary injector modules on the LT-5. They are not made anymore, so you'll have to see if you can locate one. Check your FSM for the locations in your car. Only real way to test is to put the replacement in your car and test response. If it still fails, swap it to the other one and retest. If you can confirm that the replacement came from a fully functional LT-5, that is ideal.

If one has failed, you will only run on 4 secondary injectors, not 8, making the engine shudder when in full power mode.

Best Regards,

Steve Schroder
Crossed Flags Performance, LLC

Sent from my SM-G950U using ZR-1 Net Registry mobile app

[402Z]

Found out the car had original injectors. Replaced them with brand new Delphi ones and got a chip installed at SGC. Car runs great now. Thanks for your input everyone!