82-92 V8 Tech V8 Camaro General Topics.

1989 Iroc Z fuel injection issues and vacuum routing

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Old May 20, 2026 | 03:46 PM
  #1  
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Default 1989 Iroc Z fuel injection issues and vacuum routing

Just a quick introduction. I am a retired mechanic. Retired during 2nd gen Camaros. Yep, I'm a old fart. This car does not belong to me. It's my electrician buddy's car. He bought it with this problem and somehow his problem ended up in my garage. So the problem is, sometimes it won't start. I think mostly when it's warm. It always runs like crap. He had it towed to me but it ran good enough to drive it in the garage. 45 minutes after shutting it off, I began doing diagnostics. The first thing I noticed is a mixed bag of injectors and all the electrical connectors missing their retaining clips. It appears as though two injectors have been replaced (#1 and #7). That said, I started with fuel supply and found no residual pressure in the fuel rails after only 45 minutes of sitting. the first time I turned the key on, fuel pressure jumped right up to about 43 psi. Turned the key off and the rail pressure dropped to zero in about 20 seconds. The second try, it went to 43 psi but only dropped to about 40 but slowly dropped off after. My first thought was at least one injector hanging open. I checked the oil level and found it one inch high on the dipstick and smelling like gas. The fuel pressure regulator seems ok. I kept on with checking things by testing the resistance of all 8 injectors as follows
#1 16.8 ohms #2 12.4 ohms
#3 13.1 ohms #4 14.9 ohms
#5 12.5 ohms #6 12.7 ohms
#7 16.4 ohms #8 12.5 ohms
Electrically not great but I think the bigger problem appears to be on or more leaking by when not running. I'm planning to do a compression test next. If that comes out ok, I'm going to suggest all new injectors and while the plenum is off, replace the regulator.
 
Old May 21, 2026 | 07:28 AM
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I would suspect ingnition control module
 
Old May 21, 2026 | 11:41 AM
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Those injector numbers are wacky.
I have a fully restored '89 1LE and am using these injectors, as mine were all over the place as well.

https://www.racetronix.biz/p/19-lb-h...jector/01d041x

Made a huge difference in how the engine performs.

Mike.
 
Old May 21, 2026 | 05:08 PM
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I haven't found my compression tester yet but do have some additional information. I did check the ignition timing. Tag says 6 degrees BTDC. It's about 8 No biggie. Decided to get up to temperature and retest the injector coils. They were all close to the cold measurements except #6. when the engine is hot, that one goes open line.
Where does the tach get it's signal? It appears to be reading way high.
 
Old May 21, 2026 | 05:23 PM
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I haven't found my compression tester yet but do have some additional information. I did check the ignition timing. Tag says 6 degrees BTDC. It's about 8 No biggie. Decided to get up to temperature and retest the injector coils. They were all close to the cold measurements except #6. when the engine is hot, that one goes open line.
Where does the tach get it's signal? It appears to be reading way high.
 
Old May 22, 2026 | 10:59 AM
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Was the engine up to temp and did you disconnect the tan / black stripe wire before checking the timing? It's required.

Mike.
 
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