Injector issue with 1990?

[cp1joel]

Hi all,

I own a RHD 1990 ZR1 here in Brisbane, Australia.

It has had some work done to it, reground camshafts, and new headers. Also I recently installed a calibration chip by Marc Hailbeck. Car has 20k Miles.

Before I installed the chip, the car was idling high, hesitation followed by a massive surge of acceleration. Also was difficult to start when the engine was warm.

Hats of to Marc, very impressed how much his chip sorted out the idle and acceleration problem.

Anyway to the problem. The car is great when cold, but after it warms up there seems to be an issue. After coming to stop - start highway traffic, the cars Idle was becoming erratic. More so when travelling very slowly, clutch in, out etc. Feels as though it is going to die and running rough but doesn't drop below 900 RPM. Once the traffic cleared, I noticed that it was lacking power. Once I got up to highway speeds the power seemed to come back and was back to normal.

Seems to be a bit of shaking in 3rd gear with WOT.

Also the car has a very noise flywheel, which was becoming very apparent when idling, moving slowly. According to Marc, he believes this is an injector issue which is causing an imbalance.

Would appreciate some help with this. Would be great to finally getting the car running great.

note - the injectors were replaced a couple of years ago.


Regards

Joel

[George Maz]

Quad-pack.
There are two, one may be bad.
Mine felt down on power, rough, like it was down a cylinder. Put it in fourth gear at 20mph, let it roll up to 40mph ...if it shudders, you're down a cylinder.

At idle, it sends a bad harmonic down the exhaust, which sounds like a chattering flywheel. I actually have a video of this. https://youtu.be/MHc84mj3zgQ

RH drive....cool.

[efnfast]

If the injectors were replaced with OEM, they still are not ethanol tollerant. Do you use guy use ethanol down under?

[Paul Workman]

If it hadn't been said already, I'd be looking at injectors.

If I'm not mistaken, Dynomite (Cliff) has one of my posts from like 8 or 9 years ago in his SOLUTIONS archive with a color graphic showing the pin-out for the injector relay connectors. From there you can measure the resistance of the injectors to determine which (if any) are bad.

And, to Steve's point, does your fuel contain alcohol? And, too, my injectors were replaced when I bought the car...with New Old Stock (NOS) injectors. Two years later I was having what sounds like the same idle issues your are PLUS some full throttle issues as well, also related to the bad injectors.

Get the motor up to operating temperature before measuring the resistance (to avoid a temporary "normal" reading), and then measure the resistance of each injector (coil).

And, by the way... What you're experiencing doesn't sound like anything too difficult to fix!

[cp1joel]

Originally Posted by George Maz

Quad-pack.
There are two, one may be bad.
Mine felt down on power, rough, like it was down a cylinder. Put it in fourth gear at 20mph, let it roll up to 40mph ...if it shudders, you're down a cylinder.

At idle, it sends a bad harmonic down the exhaust, which sounds like a chattering flywheel. I actually have a video of this. https://youtu.be/MHc84mj3zgQ

RH drive....cool.

George, would you mind confirming what you mean by Quad-Pack?
Interesting about being down a cylinder. If I was down a cylinder, would it be down continuously? Excuse my limited mechanical knowledge ( I am slowly learning ! )

And for the full power to come back once I regained highway speeds?

Also the video you sent me, the knocking sounds like it has a certain rhythm, where mine is more spontaneous, louder then softer. I will take a video when I can.

Originally Posted by efnfast

If the injectors were replaced with OEM, they still are not ethanol tollerant. Do you use guy use ethanol down under?

Steve - as far as I can tell from the previous owners receipts, the Injectors were supplied by Jerry's Gaskets in 2015. The type I am not sure about. I normally fill the car with 98 octane fuel which does not contain ethanol here. We do have ethanol fuels but are used in 91 RON.

Paul - Will look into finding this diagram and hopefully it is injectors.

This has only ever happened once before when I felt the car was lacking power. Normally the car will go like a bat out of hell! The car doesn't get driven much so may be contributing to the issue. Usually on starting ( cold starts are fine) the engine will shake, looks like it is hunting for idle. Not sure if this is normal?


Thanks for your help with this guys. Much appreciated.

Joel

[efnfast]

98 octane? DUDE!

[cp1joel]

Originally Posted by efnfast

98 octane? DUDE!

What is the issue with this?

This is also the fuel Marc calibrated the chip for.

Cheers

[DRM500RUBYZR-1]

Originally Posted by cp1joel

What is the issue with this?

This is also the fuel Marc calibrated the chip for.

Cheers

98 Octane!


We are all just jealous!
Would love to pull up to a pump and get 98 octane!!!


We need to buy Race Gas to get that kind of octane, and it is not on every corner!


Very cool!
Marty

[BigJohn]

Yep we all need 13 to 1 compression!

[Paul Workman]

Originally Posted by cp1joel

George, would you mind confirming what you mean by Quad-Pack?
Interesting about being down a cylinder. If I was down a cylinder, would it be down continuously? Excuse my limited mechanical knowledge ( I am slowly learning ! )

And for the full power to come back once I regained highway speeds?

Also the video you sent me, the knocking sounds like it has a certain rhythm, where mine is more spontaneous, louder then softer. I will take a video when I can.



Steve - as far as I can tell from the previous owners receipts, the Injectors were supplied by Jerry's Gaskets in 2015. The type I am not sure about. I normally fill the car with 98 octane fuel which does not contain ethanol here. We do have ethanol fuels but are used in 91 RON.

Paul - Will look into finding this diagram and hopefully it is injectors.

This has only ever happened once before when I felt the car was lacking power. Normally the car will go like a bat out of hell! The car doesn't get driven much so may be contributing to the issue. Usually on starting ( cold starts are fine) the engine will shake, looks like it is hunting for idle. Not sure if this is normal?


Thanks for your help with this guys. Much appreciated.

Joel

Being that Jerry supplied the injectors in 2015, I'm sure you have the alcohol-tollerant version. But, if you have NO alcohol in the fuel anyway, then it is a moot point. Prolly something else, e.g., fuel pumps/pressure - that sort of thing, maybe.