Plenum Pull...Parts List Varification...

[Jim Nolan]

If you are putting that much into it then replace the wires. There is no sense going into it later when it can be done now. On another note check the torque on the injector housing bolts. The first time I took mine off half of them were finger tight. It's my understanding this is common.

[tomtom72]

Okay, my two cents on wires. They are basically carbon core RF wires. Consider the environment of an LT5. I r&r'ed mine at the 15k mark because I had to do injectors. I found a deal on Magnecore 10mm wires on e-bay for about half price so I bought them.

Was that a good choice? I don't know, Honestly it was proly a waste of $140.00 as I'm sure the GM replacement wires would do just fine. It's the environment and the material's reaction to the environment more than just time or mileage in MHO.

My spark plug choice is based on GM said that the 41-602 plug crosses to a FR2LS plug which is NLA, and the FR2LS plugs came from BG in my car.....Besides Pete says that they work just fine in his 10 second ZR-1....so I guess they would work just fine in my slow, stock ZR-1.... and at the price I can afford to change them every year!


Tom

[| 1990 ZR-1 |]

Thanks guys. I'm sold on the spark plugs, and will replace the wires and coils too.

Any idea where i can buy the LT5 specific GM coils?
Also, any issues going with the wires form Jerry's?

[mike100]

I'm decided to reuse my stock ignition. 27k miles and only the plugs are new. It all works fine.

I'm going to either use my plug wires up, or the car will stay low mileage original- either way, it was less money out of pocket.

[| 1990 ZR-1 |]

Originally Posted by mike100

I'm decided to reuse my stock ignition. 27k miles and only the plugs are new. It all works fine.

I'm going to either use my plug wires up, or the car will stay low mileage original- either way, it was less money out of pocket.

That's kind of what I'm shooting for. The will stay low milage and will only be driven on nice weekends.

[| 1990 ZR-1 |]

Quick update. I just had a chance to measure the restitatnce of both the primary and secondary injectors after getting the car to it's opreational temperature range by running it for 30 minutes.

Here's the readout.
Primary:
#6 - 13.8
#5 - 13.8
#7 - 13.7
#2 - 13.8
#1 - 13.8
#8 - 13.6
#4 - 13.7
#3 - 13.9

Secondary:
#6 - 15.1
#5 - 13.4
#7 - 13.5
#2 - 13.6
#1 - 13.5
#8 - 13.4
#4 - 13.6
#3 - 13.6

With the exception of Cylinder # 6 Secondary injector reading a little high, I belive everythgin else is well within the norm.

My secondary vacum pump works fine, and the vacum pressure under the plenum alos holds fine. The secondary intake acuators are operational.

Given the above info, what else should I trouble shoot?

[mike100]

Have a look at this video:
You tube secondary injector diagnostic vid

I actually purchased a tech1A- it's so handy for the OBD1 cars.

while your in there, check out a number of other vids from the same guy- some neat Corvette stuff (like the LT5 engine dyno runs.

I

[mike100]

It does sound like you might have an ignition problem, but if you still have the orig 1990 multec injectors, you should probably replace them anyhow. I'd also read the section on the secondary injector relays to get an idea of how they work.

[tomtom72]

Okay Gary, at this point I have to figure the coils passed the ohm test. So what's left?

2* drivers ( relays ) and 2* fuel pump, and the power switch.

The "Full Engine Power" light stays illuminated when the switch is turned to the Full Power position, right? I know that sounds odd, but on the 90's the contacts in our switches seem to have age issues. If the FEP light in the DIC is not illuminated when the switch is in the full power position there is no 2* operation.

The 2* fuel pump needs to be working also. You did the KOEO fuel pump test, right?

I'll have to look up the diagnostic chart for the 2* relays.....but I think if you read the ohms on the 2* injector coils then the 2* relays ( drivers or quad drivers as they are sometimes called ) are okay. I'm not 100% so I'll look in my FSM.

You do not get a SES light in the DIC when she starts to stumble, right?


Tom

This is a P.S. because I always forget this item. The secondary MAP sensor under the ECM bracket. That has to work also however a bad 2* MAP sets a DTC, I can't remember which for sure. I'll go look & check back with you. Sorry.

[tomtom72]

I did some checking in the FSM. I think I'm correct in thinking the the 2* injector relays are okay as you did get ohm readings. Also, the 2* MAP is okay as you didn't indicate any SES light, either steady or flickering and you didn't mention that the car stops at 3,000 rpms, that's a DTC 61. No DTC 61 eliminates the secondary vacuum system in it's entirety the way I read the diagnostic chart. I could be wrong on that though.

Therefore, I think a look see at the spark plugs is in order to see the mixture condition. Also, the fuel pump test is also a useful diagnostic tool at this point, the KOEO test. You could have some one rev the car and go stand & smell the exhaust to see if it's lean, but then you still would need the fuel pump test. Unless the 2* injector tips a blocked solid with crud I can't see what's wrong if the fuel pumps pass the test.


Tom