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1991 C1500 5.7 Issues

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Old Jan 10, 2013 | 03:33 PM
  #1  
acquarossa's Avatar
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Default 1991 C1500 5.7 Issues

Hey guys, new to the forum and hope im posting in the right area!

I had been having an issue with my truck where it would get massive fuel cut (bucking and hesitation) when in overdrive on the freeway, a slightly rough idle (would idle fine and have random hesitations, not consistent at all). Check engine light never came on so i did the usual; oil change, air filter, fuel filter, cleaned out the throttle body to no avail.

Now as of a couple days ago im getting terrible idle, and absolutely no power. feels like im driving a go kart! the service engine light came on for about an hr, then went off again.

Found a few websites that talked about not having to get a code reader and just jumping the terminals. im 99.9% sure i jumped the correct terminals but when i put the key in the on position the service engine light just flashes once then stays on.

the only other thing i can think of is when its idling really rough if i put it in neutral it idles better (not perfect, but better)

Any insight would be greatly appreciated!
 
Old Jan 10, 2013 | 05:10 PM
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Possibly a intake manifold Gasket. That engine had quite a bit of trouble with that going out and causing problems.

Welcome to Truck Forums.
 
Old Jan 11, 2013 | 06:34 PM
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gah i hope not. thats one of those repairs where its only a $15 dollar part but takes hours to do if ya dont know what you're doing...which i dont. This is my first chevy, and first 8cyl engine so a lot of this stuff is pretty new to me.
 
Old Jan 12, 2013 | 02:27 AM
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I can have the whole job done in about 45 mins. It's not that hard to do.
 
Old Jan 12, 2013 | 10:57 AM
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I would suggest getting the codes read. Try and find a place that can do a LIVE code reading too

It sounds like your truck is creating issues that are temperature sensitive

Please come back and let us know what you learned
 
Old Jan 13, 2013 | 07:31 AM
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X2 on what In2Trux said.
You have a CEL on, have the code pulled first.

Very common issue on those is cap/rotor corrsion internally.
Don't just throw those parts on it unless they are bad, you need the computer scanned.
 
Old Jan 13, 2013 | 10:35 AM
  #7  
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The cel was only on for about an hour. Does it store old codes when the cel goes off? I tried jumping the two terminals but it didn't flash any codes.
 
Old Jan 13, 2013 | 04:04 PM
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I have never had any luck reading codes on anything. I don't even mess with it any more.
 
Old Jan 13, 2013 | 06:22 PM
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Your ECM will have a history. The technician can search throw the history to find related codes and faults
 
Old Jan 14, 2013 | 07:59 AM
  #10  
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Those early ECMs don't store all codes.
Sometimes they only show certain codes while the CEL is on. When jumping terminal A-B on the ALDL if the CEL won't flash code 12 it indicates a bad ECM. That is assuming the data link has a good connection with the ECM.
 
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