ZR-1 specialist UK

[bigben]

Hello,

I have a 1990 C4 ZR1 which I am about at the end of my tether with. The story so far:

- Car would run like a bag of spanners once the engine was warm - traced this to injectors being low impedance, they were probably the originals so damaged by Ethanol
- Replaced injectors - car then ran badly at idle even when cold - found I had 'pinched' an injector wire so one of them was stuck 'ON' - fixed this no change
- Went through vacuum system tightening stuff up / replacing rubber bits - no improvement

Question is can anyone recommend a UK garage, ideally midlands based with ZR-1 experience. The above short list is in no way a reflection of the many many hours I have put into tracing the problem and I am bored of it now!

Thanks for any leads

Ben

 

[scazman]

Hi Ben.
I'm sure members will be along with other ideas, but I'd be surprised if Topcats Racing couldn't fix your issues. They're based in Bucks - so not a million miles from the Midlands. They definitely look after quite a few Vettes. Not personally used them (I'm based further south and am a very satisfied Ian Goss customer - IGS American, who would definitely be able to help, but he's London based).
Best of luck with it.
Have a look here - Servicing – Topcats Racing

 

[teamzr1]

Hello,

I have a 1990 C4 ZR1 which I am about at the end of my tether with. The story so far:

- Car would run like a bag of spanners once the engine was warm - traced this to injectors being low impedance, they were probably the originals so damaged by Ethanol
- Replaced injectors - car then ran badly at idle even when cold - found I had 'pinched' an injector wire so one of them was stuck 'ON' - fixed this no change
- Went through vacuum system tightening stuff up / replacing rubber bits - no improvement

Question is can anyone recommend a UK garage, ideally midlands based with ZR-1 experience. The above short list is in no way a reflection of the many many hours I have put into tracing the problem and I am bored of it now!

Thanks for any leads

Ben

Did you replace just the 8 primary or all 16 injectors ?
The ones you bought are they GM OEM or 3rd party ones ?
Did you check the vacuum hoses under the intake manifold for the secondaries ?

Is the fuel rail pressure like 43 PSI ?
Would help if you use a smoker and looked for slight leaks
Run any different if you have the power key on or off ?
Do you have an OBD1 scanner to see how the fuel trims, timing, ECT, MAT, etc. look like ?

I do custom tuning of GM vehicles, looking at the ECM stock calibration it is expecting
the injectors to be 22.8 lbs/hr flow ( with fuel rail pressure 43 PSI) so if the ones you installed are different either have to tune the calibration for them or buy the correct flowing ones.
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[EddyEdden]

Williams Bros, Brook Farm, Corn Hill, Bugbrooke, Northampton, NN12 8LQ might be worth a try. 01327 220777. They have worked on several club (and non club) members cars. Always eager to help.

 

[Llewelyn]

Ben I have changed the injectors on my ZR-1 and spent weeks pissing around with annoying running faults. If you've seen my youtube vids of the jonny smith barn find resurrection you'll know the pain I've been through.

I hate to break it to you but it sounds like ECM failure. The only real option is to send it to Mark Heibeck in America for repair (it costs quite a bit). I'd be happy to take a look at it with you and go through some of the checks I've done with mine. The only real way to know is to find a fellow ZR1 owner who is willing to let you try their ECM on your car or vice versa. I do know a guy... But I'm not sure if he'd be up for it (I can ask) .

I'm in Rearsby LE7 if you want me to have a look, or I could pop over to you depending on where you are.

 

[bigben]

Ben I have changed the injectors on my ZR-1 and spent weeks pissing around with annoying running faults. If you've seen my youtube vids of the jonny smith barn find resurrection you'll know the pain I've been through.

I hate to break it to you but it sounds like ECM failure. The only real option is to send it to Mark Heibeck in America for repair (it costs quite a bit). I'd be happy to take a look at it with you and go through some of the checks I've done with mine. The only real way to know is to find a fellow ZR1 owner who is willing to let you try their ECM on your car or vice versa. I do know a guy... But I'm not sure if he'd be up for it (I can ask) .

I'm in Rearsby LE7 if you want me to have a look, or I could pop over to you depending on where you are.

I am in Northampton so not a million miles away.

I have a plan to refit the old injectors and see if that gets me back to step one (the car then had decent idle but started to run badly when warm) after that the ECM does become suspicious, although it would be odd for it to break at the exact time the injectors were swapped.

 

[teamzr1]

Odd issues with the ECM is due to GM mounting it high, off the firewall so heat raises and ECM is living in that hot heat soaked temps
The ECM has a multi layered PCB so what happens as ECM ages, hot temps causing the layers to expand and contract again in cooler temps. Really needing more heat sinks on ECM case

Over the years of this happening the layers left apart from each other and the circuits either degrade or loose connections
ECM should have been located as GM learned the hard way and starting with C5s the PCM is mounted close to the ground and is hidden from the engine bay temps

I would not rule the ECM degraded yet until the correct 16 injectors replaced and all those vacuum lines under the intake checked or replaced and a OBD1 scanner used to see how every is functioning and if not what functions need to be corrected

Keep in mind on a cold start the coolant temps below like 130F degrees, the ECM is in "Open Loop" and hence ignores the engines feedback sensors
Over that temp a OBD1 scanner should see the ECM go into "Closed Loop" and command as to what the sensors are telling it
So if any issues such as injector flow or vacuum leaks would not be seen until then