backfire through intake, car stalls at idle - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 01-19-2005, 01:21 PM   #1
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Default backfire through intake, car stalls at idle

this problem has just started happening. i'll have to give it gas to get it started in the mornings, and sometimes i will just hear a loud pop while trying to start the car. the car is backfiring through the intake, causing the airbox to shake, and that'* the loud pop that im experiencing. i looked at the airbox last night and noticed its pretty much in pieces from all the times its been doing this, its only been doing it for about a week! but i have been experiencing the stalling at idle for a little over a month. pulling out of driveways, sitting in traffic, waiting at red lights, the car just dies all the time. and normally it idles okay, the rpms sometimes go up and down a little bit but its not running "rough". i replaced the upper intake over the summer, and while doing so replaced the dexcool with the regular green antifreeze. i remember having trouble passing smog about a month after the intake was replaced, and it would always take me 3 or 4 tries to get it started. but it never stalled until like i said, about a little over a month ago. i went to autozone to pull the codes and didnt come up with anything. i have been using a fram airhog air filter for about 3 months, oil pressure is fine, replaced the fuel filter a month ago, new plugs and wires, i dont know what would be causing this "backfire". but all i know for now is that i need to get a new intake... because that big plastic box is cracked and in pieces. im thinking a cold air intake type deal... what are my options?
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Old 01-19-2005, 01:33 PM   #2
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If your airbox is cracked, imagine what the inside of your engine is going through.
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Old 01-19-2005, 01:35 PM   #3
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check ur timing
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Old 01-19-2005, 01:43 PM   #4
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what should the timing be at? i thought the timing was done through the pcm. ill go to autozone later today and borrow a timing light. as for the air intake, its only been cracked with pieces broken off for about a day. i put it all back together and it will hold for a few days, but im going to need to get a new intake. can i get an aftermarket one at autozone or kragen? or do these need to be ordered online? whats a good place to get one? reading through other posts it sounds like it may be my pcm, but i have no idea. thanks for the help
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Old 01-19-2005, 02:05 PM   #5
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Your timing is controlled by the PCM.

Are you getting a check engine light? When was your last tune up? How does the car run when you're cruising? A clogged cat can also make the car run very poorly like you described.

We need more information.
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Old 01-19-2005, 02:11 PM   #6
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no im not getting any check engine light. the car runs perfectly fine otherwise, ive noticed ive been getting about 22mpg, it runs fine on the highway. the last tuneup was done when the upper intake was changed, id say 4 or 5 months ago? i just put new plugs and wires in, i put in a new air filter about 3 months ago and the fuel filter also around the same time.
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Old 01-19-2005, 02:30 PM   #7
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hrm. i was thinking fuel pressure regulator myself. symptoms seem to be about right. try moving the key to the 'run' position, and then removing it and repeating about 4 times before you start. see if that helps.

just a feeling. anyhew, if the FPR is leaking into the intake, it would explain the boom, the random non-start issues, etc...
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Old 01-20-2005, 12:44 AM   #8
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how would i go about checking the fuel pressure regulator? and where exactly is it located?

before the loud booms started happening, the vacuum lines that plug into the throttle body would pop off occasionally, due to the backpressure. but since the booming sounds started they havent popped off.. just a side note.

i tried the thing with the key today i did it 5 or 6 times and it didnt seem to help at all. every time i try to start the car it takes me 3 or 4 tries to get it running, except if the engine is warm and i shut it off and start it right up again, it will usually start right back up again.

i am really worried about driving the car with the intake craked how it is, there arent any big holes in it or anything, but i want to get it fixed or replaced with an aftermarket one asap. any suggestions?
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Old 01-20-2005, 02:34 AM   #9
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Quote:
Originally Posted by jr's3800
Quote:
Originally Posted by mkaake
hrm. i was thinking fuel pressure regulator myself. symptoms seem to be about right. try moving the key to the 'run' position, and then removing it and repeating about 4 times before you start. see if that helps.

just a feeling. anyhew, if the FPR is leaking into the intake, it would explain the boom, the random non-start issues, etc...
Thats also a possibility... And should be checked.... 207,000 is a lot of miles..
FPR wouldn't be causing this....My FPR is probably barely hangin in there...and my car doesn't do anything that he'* describing....And flooding the engine wouldn't cause the backfire....It'* timing, and I'm with JR'* first guess on this, seeing how timing is controled by the PCM....I think you're PCM is going bad.....IMO
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Old 01-20-2005, 07:39 AM   #10
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This happened to me, what it is, is the ignition is firing when the intake valve is open. Try replacing your plug wires with a high quality brand. What happend to me, is the spark jumped from the wire to another wire, and all I did was separate them a little more, but that'* because I didn't feel like investing in a new set right away. I'd suggest doing that first, and see where you get.


-justin
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