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Virtual Wrench
Virtual Wrench, Chevy Mechanic
Category: Chevy
Satisfied Customers: 14620
Experience:  35 years Master Mechanic
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1997 gmc Yukon 4x4: 5.7l..engine will backfire through the intake

Resolved Question:

i have a 1997 gmc Yukon 4x4 with a 5.7l. When the engine is cold the engine will backfire through the intake. It is then very hard to start (it seems like it tries to backfire again and again only much less severe than the first). Once it does start it runs with a bad miss for a minute or two. After it is warm the engine will run roughly and have a slight shake at idle. It has set a missfire code just once. I have replaced the cap, rotor, wires, coil, electronic spark control module, and the plugs. It has not set a code since, but still has the problem. About once every three or four times it is running the engine will run without any stumble or backfire. What do I need to look at next for a problem.
Submitted: 10 years ago.
Category: Chevy
Expert:  Virtual Wrench replied 10 years ago.

It sounds like it may be fuel related, it could be an injector sticking open, and then closing, it's hard to tell for sure, but it wont necassarilly set a code. I would recommend having the injectors professionally cleaned and then if problem persists, you may want to put it on a scanner to be able to watch live readings on the engine performance. This way you can watch the action of each injector, and see if one is falling out.

 

If you have further questions on this, please feel free to reply.

Thanks for asking!

V W

 

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