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Old 06-26-2014, 02:31 PM   #1
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Car starts, dies, and backfires?

Hey all, 02 Z28 with about 150k on the clock.

I have a problem wherein if I drive the car and allow it to reach normal operating temp, park it for a couple of minutes, and then go to start it again, she cranks, starts, then dies with a loud pop from the tailpipe.

More specifically, she will crank for maybe a second before catching. The RPMs slowly rise to about 8-900 (over the course of a second or two) then slowly fall back off until it hits about 150, where it'll stop (usually punctuated with the loud pop). She starts up immediately after that and runs (and idles) fine.

Things to note: She does have a slight miss at idle.
Does have an odd starting delay in the morning (which I believe is related to the starter relay connection)
Only does this if the car is warm and has sat for a couple of minutes. (Shutting off the car and restarting it doesn't produce the same effect)

I honestly have no idea what's causing this. The smoothness at which the idle drops leads me to believe she is still firing, but not getting enough fuel or air to produce enough power to keep running? I know a backfire is usually indicative of an improper A/F causing a misfire, but what would cause the bad A/F?

Any ideas, theories, and help is greatly appreciated.
Black '02 Z28 vert, bone stock. (For now)
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Old 06-26-2014, 10:06 PM   #2
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Re: Car starts, dies, and backfires?

Is it throwing any codes and setting off the SES light?

I'd start by cleaning the MAF. You can get a can of cleaner specifically for MAF's at any parts store. It's also possible it's the coolant sensor. However, without knowing what codes it's throwing, these are both shots in the dark...
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Last edited by BandDirector Blk98ZM6; 06-26-2014 at 10:09 PM.
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Old 06-27-2014, 09:39 AM   #3
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Re: Car starts, dies, and backfires?

Also might want to check the fuel pressure.

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Old 07-17-2014, 11:41 AM   #4
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Re: Car starts, dies, and backfires?

Well I'm going to check the fuel pressure when I get home tonight. I replaced the fuel filter last weekend in the vain hope that it would be that easy... Shoulda known XD

Though it does appear that all signs are pointing towards the fuel pump either failing, or losing signal. Which brings up a couple of other questions.

Edit: Tested the fuel pump today, got 50psi at key on, engine off, started it and she jumped to 60 psi. So obviously no issues with the pump. Going to try and clean the MAF next, probably plug a scanner in and drive her to work and see what sort of readings I get.

number two: If it's the pump losing signal, how can I test this? Attach a volt-meter to the wires running to the pump?

Thanks guys
Black '02 Z28 vert, bone stock. (For now)

Last edited by HappySalesman; 07-17-2014 at 09:43 PM.
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Old 09-08-2014, 08:29 AM   #5
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Re: Car starts, dies, and backfires?

Restart after heak soak and having major running issues sounds like a head gasket issue to me. Might be something to keep in mind. Hope it doesnt turn out that way for ya though.

What happens is after shut off the gaps open and allow coolant to get into the cylinders then when starting, ya cant burn coolant.

When you start it can you rev it a bit and does it clear up some?

Last edited by Suprabuilder; 09-08-2014 at 08:33 AM.
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