No or low spark #4 and #7 plugs

[DTZ ZR1]

Brothers, thank you for the pics, it does make me feel a lot more confident about doing this. I just do not want to screw it up. This is a great place for info. I will proably be doing this in two or three weeks. Life is busy and it also gives me time to research.

Jerry I will get with you on the gaskets.

Tom I do have the factory service manual, first thing I purchased after I got the Z. Thanks for the website info.

Michael, thank you for the info and pics. I also like the schematic for the bolts.

Jim, thank you for the info on flushing fuel rails and checking the coil packs.


Thanks, DT

[jonszr1]

what should the resistance be on the primary and secondary.? i have never been able to find those figs

[Kb7tif]

Originally Posted by DTZ ZR1

I have a 90 ZR-1 and I was having a problem with my engine running rough and also having SYS flash on my display. I changed the battery because I did have problems with it and that took care of the SYS. At first it seemed to clear the engine problem. Took the car on a 400 mile trip over the 4th, she performed flawlessly. This week she started to idle real rough and felt like a cylinder was miss firing. I changed the easiest thing the plugs, I put AC 41-602s in. I took 1,3,5, & 7 out and replaced them. I started the motor and it still was idling rough. I then took out 2,4,6, & 8, when I took #4 out it was wet. I replaced those four and started the motor. It idled better, but still not what I liked. I then took #4 wire off, idle did not change. Took all the other wires off, I could hear the spark jump and engine idled rougher except for #7, there was no change. I looked at my service manual and found that they are off the same coil pack so I figured that I would replace all four. The question is while I have the plenum off what else should I change or look at? Also is there anything I need to be aware of when removing it? What would be a good coil pack to replace them with? Thanks for the help.

You mentioned 1 spark plug was wet, this is pry a fuel injector sticking open, are the injectors stock.

[tomtom72]

Originally Posted by Kb7tif

You mentioned 1 spark plug was wet, this is pry a fuel injector sticking open, are the injectors stock.

Good catch! DT was 7 wet also? I would think the chances are better than even money it should have been, although Jeff has seen coils have a one tower failure. Again, not trying to spend your cash for ya, but the word is that the OE multi-techs don't react well to cleaning attempts. It's a judgement call on your part about the injectors.....on the early cars 90 & 91(?), the alcohol in the gas will eventually get them.

Oh, DT, You're welcome!

[Jim Nolan]

Check the injector housing bolts. On mine the inside rows on both sides were finger tight.

[Z51JEFF]

Its not necessary to drain the coolant,maybe a gallon at most as long as your not taking off the coolant pipes.Couple tips,one of the biggest mistakes made when putting the plenum back on it pulling one of the hoses off,mainly the cork screw line,ask me how I know.A good trick is to put the line down in the rubber fitting,make sure its seated,wrap a piece of tape around the line as close to the fitting you can get it.The reason for this,as you lower the plenum in place watch the line,if it has come out of the fitting you can tell BEFORE you button up the plenum.Mine pulled out and couldnt tell by looking at it,it was sitting at the top of the fitting,looked like it was still in the fitting.The only reason for the tape is to use as a visual thing,nothing more.Plugging the harness back into the spark jobber on the bottom of the plenum is a pain.Bending the connectors is really easy and getting the bolt started is also a pain.

Originally Posted by Z51JEFF

Couple tips,one of the biggest mistakes made when putting the plenum back on it pulling one of the hoses off,mainly the cork screw line,ask me how I know.

His car does not have that as the EVAP system is in the front of the car.

[DTZ ZR1]

I will be changing out the injectors, I believe that they are stock. It does not look like anyone had the plenum off. The factory plug wires are still on. I figured on changing the packs and wires too and anything else that might be bad.

Jerry's gaskets come in two different thickness, Which would be better?

I am trying to clear my schedule so I can start on it this weekend. I do not think I could wait three weeks to drive her again.

[DTZ ZR1]

I had already changed it and started the car to see if things changed and I did not go back and take 7 out. I know I should have.

DT

Originally Posted by DTZ ZR1

I will be changing out the injectors, I believe that they are stock. It does not look like anyone had the plenum off. The factory plug wires are still on. I figured on changing the packs and wires too and anything else that might be bad.

Jerry's gaskets come in two different thickness, Which would be better?

I am trying to clear my schedule so I can start on it this weekend. I do not think I could wait three weeks to drive her again.

I prefer the thicker gaskets. Less likely to tear under future removal.

Give me a shout on the coils and plug wires I stock them.