MY 94 K1500

  • Tiny
  • zdaily
  • 1994 Chevrolet Silverado
  • 190,000 miles

My 94 k1500. 5.7 tbi. Is having some driving problems. Idling the truck is sound, but from first gear to 3rd it is kind of all over the place. I can't hold a constant speed. It fluxuates speed and rpm. I had the motor rebuilt and the machinist put a bigger cam in the truck but I don't know what to do with the pcm. Where it is, what it does or anything. If you could help me figure this out I'd be greatful

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Thursday, February 14th, 2013 AT 6:37 PM

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  • Tiny
  • hmac300
  • Expert
  • 43,759 posts

Check for a vacuum leakthe gasket under the tbi blows and cause that also check the hose going to the map sensor on firewall, if it's soft get anew one because it may be sucking together not allowing map to work right. Check fuel pressure it should be 9-11 psi.

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Thursday, February 14th, 2013 AT 7:58 PM
  • Tiny
  • zdaily
  • Member

Had a mechanic check all pressure, and timing says it's running perfect. The hose on the map sensor is hard as a rock. My cold air k&n intake is missing a stud because of the install before I had the truck. The hole for the stud is about a quarter of an inch. I took the throttle body off the truck and cleaned regasketed and added new filters to the fuel injectors.

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Friday, February 15th, 2013 AT 6:38 PM
  • Tiny
  • hmac300
  • Expert
  • 43,759 posts

If the hose is hard as arock it shold be like anew piece of vacuum hose replace. Is it leaking ari around the stud? It shouldn't otherwise that will cause problems for maf. The pcm shold be in the kick panel on passenger side but dont' think that is the problem it might be a prom but that should show up when scanned. And you probably can't get another prom now anyhow due to age. Can't offer any other suggestions on this one.

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Friday, February 15th, 2013 AT 6:52 PM

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