1990 Cadillac Fleetwood misfire

Tiny
KDOXEY
  • MEMBER
  • 1990 CADILLAC FLEETWOOD
Engine Mechanical problem
1990 Cadillac Fleetwood V8 Front Wheel Drive Automatic

I have a 1990 cadillac fleetwood with 137000. Miles, just bought it, was well taken care of and garage kept, oil was changed regularly. Engine has a miss. I've changed the plugs, wires, dist. Cap and rotor button and checked for vacuum leaks and still have a miss. One plug was smutted up. Do you have any suggestions? If it were carbon buildup on a valve would seafoaming the engine work? Are there any problems with the 4.5 litre port fuel injection engines that you know that I might check for a misfire?
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Tuesday, September 2nd, 2008 AT 8:58 PM

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Tiny
SUBS0N1C
  • MEMBER
Hi kdoxey, I also have a 1990 Cadillac Fleetwood 4.5 L port fuel injection. I also have a misfire. Here's what I can tell you.

It's possible that you have to high of fuel pressure which caused one of the injectors to fail. When an injector fails, it may inject too much fuel or too little, ending up with a rough run. It can be a single injector effecting a single cylinder. Or it could be all of them, I doubt it though.

I am about to do the work to my car, that being: take out one injector causing a misfire in a single cylinder, and replace it with a new one, then change the seals and o-ring.

I will then do routine maintenance on the spark plugs and wires. I already have replaced the Distributer and all of its components which have no solved the misfire.

So all in all, I will be replacing an injector, seals, and wires and spark plugs.

My suggestion for you is pull so codes, and post them for me, and I'll try and help you further.

I will also let you know how the vehicle runs after I finish the work. Hope this gives you an idea of what direction to go in.
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Wednesday, February 29th, 2012 AT 5:24 PM
Tiny
WRENCHTECH
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[quote]It's possible that you have to high of fuel pressure which caused one of the injectors to fail. When an injector fails, it may inject too much fuel or too little, ending up with a rough run. It can be a single injector effecting a single cylinder. Or it could be all of them, I doubt it though. [/Quote]

No, forget that theory.

Start out taking a compression test and testing injector pulse on that cylinder using a noid light.
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Wednesday, February 29th, 2012 AT 5:34 PM
Tiny
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Alright, I already did that, I took a flat head screw driver and stuck one end In my ear and the other on each injector, I found one that does not have any sound, like a clicking sound. And with the probe light, it doesn't light up.

The only thing I don't have acces to is a compression test.
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Wednesday, February 29th, 2012 AT 5:38 PM
Tiny
WRENCHTECH
  • EXPERT
You need to get a compression tester and a noid light. Don't stick that test light around the injector wires unless you want to risk buying a computer.
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Wednesday, February 29th, 2012 AT 5:42 PM
Tiny
SUBS0N1C
  • MEMBER
Alright. I read somewhere else that a guy bought a new computer for cheap and completely fixed the misfire. Could it just be a bad sensor or connection?
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Wednesday, February 29th, 2012 AT 5:47 PM
Tiny
WRENCHTECH
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This isn't even your question. You need to start a question of your own.
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Wednesday, February 29th, 2012 AT 6:06 PM
Tiny
CADIEMAN
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Youll need to have your engine put on a scope and see if same cylinder as the bad as the injecter.
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Wednesday, February 29th, 2012 AT 8:32 PM

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