The engine is not running on 4 cylinders

Tiny
ALYCAT38
  • MEMBER
  • 1991 CADILLAC EL DORADO
  • 120,000 MILES
It is the 4.9 v8 it is getting fire on all cylinder but only running on 4 it skips every other cylinder
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Tuesday, November 15th, 2011 AT 9:52 PM

7 Replies

Tiny
ASEMASTER6371
  • EXPERT
I would start with basics. A compression test. Fuel pressure check, spark test.

The injectors need to be verified that they are firing and allowing fuel into the cylinder. The distributor needs to be checked as well that it is passing the spark to the cylinders.
Check for vacuum leaks as well. The intake is a common failure for its gaskets.
That would be my starting point.

Roy
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Tuesday, November 15th, 2011 AT 10:07 PM
Tiny
ALYCAT38
  • MEMBER
It is firing on all 8 I would think it would be a fuel problem but it hits on 1 skips 8 hits on 4 skips 3 hits on 6 skips 5 hits on 7 skips 2
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Tuesday, November 15th, 2011 AT 10:15 PM
Tiny
ASEMASTER6371
  • EXPERT
Ok, you still need to look at injectors and a vacuum leak. Did you put a vacuum gauge on it?

Roy
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Tuesday, November 15th, 2011 AT 10:19 PM
Tiny
ALYCAT38
  • MEMBER
No didnt have time to check it out real good but I have never seen a engine skip every other cylinder
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Tuesday, November 15th, 2011 AT 10:33 PM
Tiny
ASEMASTER6371
  • EXPERT
Let us know how you make out
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Tuesday, November 15th, 2011 AT 11:21 PM
Tiny
ALYCAT38
  • MEMBER
Ok thanks for the help
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Tuesday, November 15th, 2011 AT 11:24 PM
Tiny
FACTORYJACK
  • EXPERT
2, 3, 5, and 8 are supplied power by injector fuse 5 in the underhood relay center. Check this fuse and more than likely you will find it open. The ground side of each injector is controlled by the PCM through individual drivers. A faulty ecm would most likely result in one, or another cylinder with no injector fire. If you find the fuse open, either the power side of that respective bank of injectors is shorted, or most likely an injector(s) is faulty pulling too much current. Check the resistance of the injectors(all 8) and you would look for 15 to 17 ohms being good. Any less need replaced. 1991 did have injector problems.
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+1
Wednesday, November 16th, 2011 AT 4:28 PM

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