Running on 7 Cylinders

[Jim Stanley]

My 1990 was running great until today. Note: The car has 31K miles and I drive it about 1500 per year. When I started it up I could detect a miss. As I drove it the miss became more apparent. All of the gauges read normal and there were no warning lights. At idle it made a helluva racket, especially with the AC on. I stopped at a local shop and the mechanic said I was getting spark to all 8, so probably not a coil. He thought a fuel injector had gone bad. Sounds reasonable I suppose. A couple of questions for you seasoned Z folks:
1) Can a clogged injector be cleaned?
2) Do they all have to be replaced? (I am going to try to find out if they were changed by the previous owner).
3) Why would the AC cause more rattle?
4) If not a fuel injector issue, then what are some other probables?
5) Would it make sense to check compression and spark plugs?

Thanks for your thoughts and recommendations.

[jss06c6]

If it's one cylinder and spark is good, your mechanic is probably spot on, especially with very little driving.. do have the original injectors? If so, ethanol is probably part of the problem..

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[Jim Stanley]

Originally Posted by jss06c6

If it's one cylinder and spark is good, your mechanic is probably spot on, especially with very little driving.. do have the original injectors? If so, ethanol is probably part of the problem..

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Thanks for confirming.

[Jim Stanley]

Thanks Jerry, for the additional information!

[A26B]

Originally Posted by Jim Stanley

My 1990 was running great until today. Note: The car has 31K miles and I drive it about 1500 per year. When I started it up I could detect a miss. As I drove it the miss became more apparent. All of the gauges read normal and there were no warning lights. At idle it made a helluva racket, especially with the AC on. I stopped at a local shop and the mechanic said I was getting spark to all 8, so probably not a coil. He thought a fuel injector had gone bad. Sounds reasonable I suppose. A couple of questions for you seasoned Z folks:
1) Can a clogged injector be cleaned?
Sometimes but not recommended on 90~92 w/original injectors
2) Do they all have to be replaced? (I am going to try to find out if they were changed by the previous owner).
You should replace all 16 with new.
3) Why would the AC cause more rattle?
Additional load on the engine
4) If not a fuel injector issue, then what are some other probables?
Being a 1990 & spark on all 8, it's 95% likely injectors
5) Would it make sense to check compression and spark plugs?
Plugs; yes, just in case, compression; not something that would fail suddenly.

Thanks for your thoughts and recommendations.

Jerry

[Ccmano]

Originally Posted by A26B

Jerry

What Jerry said is 100% one the money.
H

[Jagdpanzer]

In light of the fact it’s a 1990 model year good chance it’s a bad fuel injector. Here are instructions how to check the coil resistance on the injectors without having to remove the plenum:
http://www.zr1specialist.com/HAT%20W...in%20Place.pdf


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[Jim Stanley]

Great article, thanks Phil. I will try it out.