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Hello all!!
I have a 97 chevy p/u 5.7 vortec with what I believe is an intake back fire. Normally the truck will start and run fine, when it sits overnight. Sometimes when I start it after it sits for around 1-4 hours it will sound like it back fires in the intake while trying to crank the engine and after the engine starts it runs rough for 15-20 seconds and then runs fine. I know that spider injectors are a problem with this engine and possibly fuel pressure regulator? I would like some advice on where to start as spider injectors are costly and labor intensive.
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Are you losing coolant? How old are the ignition componenets? (plugs,wires,distributor cap)etc.
The reason i asked if you were losing coolant is if you have a head or intake manifold leak you could be getting coolant into a cylinder. It would partially hydraulic lock when cranking (backfire sound) and make it run rough on startup until the coolant burns off.
I have seen a few issues similar to yours and it turned out to be the distributor cap (thanks TSB.) They have an odd design, and will appear to be fine, but they can develope shorts between the spots where one line gets close to another. You’ll understand what I mean when you remove it and look on the underside of the cap. Make sure you keep the spark plug wires organized. Good luck
Yes, those spider fuel injection systems can cause some headaches…. The fuel pressure regulator is a known problem…
Read through this link, it discusses the issue and how to fix these problems in detail…
http://troubleshootmyvehicle.com/gm/4.3L-5.0L-5.7L/testing-the-spider-fuel-injector-1
Karl
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