ZR191

My Z runs rough when power key on at around 4000RPM on, like it has a rev limiter
Coils, plugs, secondary solenoid, have been changed and still ran strong for a while and the shutter came back. Heiback is testing the ECM on another Z. I need HELP PLEASE!!!!Only happens when power key on, when off runs good. Also the vacuum pump is new and working fine, all vacum hoses check, and railing are free to move.
Also fuel pump was change 2 years ago

C6FirstVette

Have you tried to pull any codes off of the ECU?

sal826

Have you replaced the fuel injectors yet? - many times the secondaries go bad because they are not used enough.

ZR191

The problem comes on all of a sudden, if it was the injectors it would continue to do it.

ZR191

This car works with something call tech1, it does no tell you much, like the newer cars

ccmano

Injectors... sounds exactly like what mine did when injectors went out. If they are originals you will need to replace them all.
H

ZR191

That will be the next step, I already bough some new primary and secondary injectors. Thanks

LT5corsa

Where do you live? (depending on where you live, maybe somebody can help) Have you gotten gaskets yet?

www.jerrysgaskets.com




David

ZR191

I live in Mami

YorkL8apex

Should be able to pull codes, I had something simmilar when my O2 sensor went bad. Fairly easy fix, buy Bosch from NAPA not GM, same aprt at 20% of the GM price if that is the issue.

If you don't know how to pull codes let me know. On a 91 you can pull them with a paper clip.

I'd guess injectors though, had that happen too, if its that try FIC (Fuel Injector Connection)

ZR191

How do you do that?

turbo-max

For GM domestic vehicles made before 1995, the diagnostic connector is located under the dash panel by the driver side. To get the check engine codes to flash in your dash panel, use a jumper wire or a paper clip and connect terminals A and B of the diagnostic connector. Turn your ignition key on with engine off and the codes should start to blink. All codes should start with code 12 which is one long flash followed by 2 short flashes. This code 12 means the diagnostic system is normal and will repeat itself continuously if there are no trouble codes. Otherwise, code 12 will flash 3 times before flashing the fault codes.

TommyL

Secondary injectors! but if you change them do all 16.

YorkL8apex

If you pull the codes write them down. I (and others) have a list of the descriptions of the codes if you post them up.

ZR191

Right now the ECM is been tested by Mr. Heiback, when I get the ECM back, I will get the codes, I have a friend that can conect the teck-1 to the car!

Aurora40

There are two things that happen when you turn the power key to full and then mat the gas. The secondary butterflies open, and the secondary injectors take over half of the fueling duties.

If your car is running rough, you need to make sure each of those is happening properly.

Mr. Gizmo

Its the injectors.

CorvetteRanch

I had the same prob. Went and bought a set of GP-Sorensons from White Racing. More like LS series injectors. Unless you're die hard and want to keep the car like original a new set of AC/Delco Rochesters will run you 132 bucks a piece. GPs are half that and up to modern efficiency. Half the crap on the motor is to beat emissions and gas guzzlin' tax. While I commend GM on that, I hate ( I say again, hate) it when engine lights come on for BS like O2 sensors etc. Dear EPA..suck it!

ZR191

I replaced the 16 injectors for new DELPHI ones....took me the hole day and the car runs exactly the same as before , like it has a rev limiter, So is not the injectors because the are NEW. With the power key on ,it runs rough and without runs fine.

Mr. Gizmo

when you had the plennum off, did the secondary butterflies open and close freely without binding?

On my 91 zr1 the secondaries were binding. As i recall on the assembly line way back in the day i remember gordon kilebrew on the corvette action line said the acuators were installed backwards on the engine assembly line on some of the motors. Mine would behave the same way it would just stop revving at about 5500-5800 rpm until i corrected it - fixed the acuators and made sure everything was moving freely. -That was back when the car was fairly new - but just out of warranty. Then a couple of years ago, it started running rough when i had the power key on, and accelerated hard with it. if the power key was off and i floored it - it ran smooth. I replaced the secondary injectors then everything was fine,