Back firing though the intake

Tiny
ERICK BRENGLE
  • MEMBER
  • 2003 BUICK LESABRE
  • 3.8L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 169,000 MILES
Sometimes at night when it's cold I back fire through the intake. Happens right after I drive it and start it up, twenty minutes later once it blew off the PVC valve. I have to replace the housing last time it blew off vacuum lines. Sometimes at work in day I start it and let it idle and I can hear little piping sounds almost sounds like when a spark plug wire arch's against metal. I have all new plugs, new wires, new fuel injectors, and new ignition control module. Plus it seems takes longer to start up, but when I press the gas petal at rev it up upon start up it evens out.
Saturday, December 22nd, 2018 AT 8:18 PM

4 Replies

Tiny
HARRY P
  • MECHANIC
  • 2,292 POSTS
There are a lot of things that can cause a backfire through the intake. Low fuel pressure, bad spark plugs, ignition timing, to name a few. Here's our general guide on the subject: https://www.2carpros.com/articles/engine-backfires-while-running

A quick check on Prodemand (one of our resources) shows the number 1 cause of backfiring through the intake in this car to be ignition related (coil, ignition module, spark plugs, wires) and #2 would be fuel pressure related (fuel pressure regulator, fuel pump). Since you've already basically ruled out #1, I'd check the fuel pressure. You can borrow a fuel pressure gauge from the parts stores and check it yourself. Here's a general how to guide on that: https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

With the key on, and engine off, you should get 48-54 PSI. Any less will cause issues for you. Since your problem seems to occur most after the car is warm, you should run the test when it's cold, and again after the car has been driven for a while.

Finally, unfortunately, we don't communicate through phone calls or emails, We keep everything on here.

So check it out and see what you find. Let us know and we'll go from there.

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Saturday, December 22nd, 2018 AT 9:36 PM
Tiny
ERICK BRENGLE
  • MEMBER
  • 2 POSTS
Thank you. I will check ASAP.
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Saturday, December 22nd, 2018 AT 9:47 PM
Tiny
ERICK BRENGLE
  • MEMBER
  • 2 POSTS
Just a quick note the fuel pump was replaced last year brand new so could it be the FPR? Today I pushed on the little valve on the FPR and gas came out looked like a tire valve stem.
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Monday, December 24th, 2018 AT 11:31 AM
Tiny
HARRY P
  • MECHANIC
  • 2,292 POSTS
Aftermarket fuel pumps sold at the local parts stores can be pretty crappy. For example, I replaced the one on my 2002 Chevrolet blazer with 150,000 on it, then again with 170,000 on it, then with 200,000, and two weeks later with 201,000 on it. I've gotten so tired of dropping the fuel tank that I cut a hole in the floor board to create an access panel now. Thankfully I have a lifetime warranty, so they just keep giving me new ones. The point is definitely check the pump. And if you haven't replaced the filter, do that too. It should have been done when you replaced the pump.
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Tuesday, December 25th, 2018 AT 11:36 AM

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