davkat

Hi guys this is my first post. First a little history, two years ago we bought a 91 Z with the 368 Lingenfelter package. The first year we had it no problems. The second year I get it out of storage and no problems at first, but about a week later it started running rough like it was running on 7 cylinders. I put fresh gas in it, a new fuel filter, new plugs, and a bottle of Lucas Oil Octane Boost. About a week later I was running it down the highway and I felt it come out of it. It ran fine till last August, and it started doing it again only this time I noticed if I pulled over shut it off started it sometimes it would run fine. Now it feels like it is running on 7 cylinders again. At idle I started pulling plug wires, every plug wire I pulled made it run worse except #6 but it has spark there. The injectors were replaced in 04 by Lingenfelter. I have searched the web, I don't trust any of the garage's around here and to add insult to injury I've been laid off since last March. So any help you guys can give me will be greatly appreciated. Thanks

Aurora40

I would suggest checking the injector resistance, as well as the coil pack resistance, and the fuel pressure.

FWIW, for me when my injectors were going, the car drove better at heavy throttle, and rougher at light throttle. When the coil packs were going, it was much worse with throttle, but seemed ok at idle and very light throttle, which made it quite hard to diagnose. All plug wires showed spark idling in the garage.

FU

Sounds like your injectors .
Head over to the forum http://www.zr1.net/forum/index.php

pst......there is a bunch of ZR1 people that are great with LT5's in your State. Seek them out , great group.

lbs90ZR

If the resistance checks good on all, you could swap coils and see if the misfire follows, or swap injectors and see if problem follows. Could just be a spark wire also, I would swap that when swaping the coils.

For troublshooting, you might be able to reuse your plenum gasket if it doesn't tear, but if the coolant passages are still being used through the plenum, be careful it doesn't leak into the intake.

illenema

Well you have plenty of time, consider replacing the injectors, might not be a bit different flow rate maybe not, shouldn't be more then 400$
Fot the matched set with a warranty from FIC or others. 90% this is what it is.

lgaff

Macon,

Wow, I am a former Decatur resident...

davkat

Thank you guys for your time and info.

Phil DeJohn

I had a 91 with the same thing. After changing just about everything said above it turned out to be the ECM.

Rkreigh

you are surrounded by the FBI gang that know ZR-1s inside out as does LPE

Haibeck is up your way and can fix the car if you don't feel comfortable tearing into it.

could be many things wrong with it, and hook up with one of of the FBI gang and they can help

zr1 net registry is where they hang out

nice car! the lpe 368 is a very special zr1

Zproud

You looking at getting it running correctley to sell or to enjoy for the summer?

after you do the needed testing and you find you need injectors
I have a good used set of 16 oem injectors from a 91, I would get the FIC injectors if you could afford It.(about 400.00)

Good Luck

davkat

I plan on enjoying it this summer and many more. This is my dream car and I hope and pray I don't have to sell it, but if I don't get back to work pretty soon I (GULP) might have to part with her. You guys will be the first to know.

Mikey Morris

GL getting it fixed. I suspect the injectors as well.

secondchance

Do you recall which brand injectors were installed in 2004? If it was Multec alcohol introduced in gas in last 2-3 years could be starting to eat it up.

Aurora40

Multec is a design, not a brand. I put Multec injectors in mine in '05 (made by Delphi), they were rated for E10, and are still working just fine.

If they were GM parts that were NOS or something, then this probably wasn't a good replacement.

secondchance

Woops! I stand corrected. I mistakenly believed original GM brand was Multec.

Aurora40

I believe Rochester Products made the original injectors for the ZR-1. Which I suppose through various mergers and spinoffs by GM eventually was part of Delphi...

I suspect the actual GM injectors are the same old ones that were used in 1990. But the Delphi ones have been updated for modern fuels. The manufacture date on mine was within a year of when I bought them, and as I said, they were rated for E10, unlike the originals.