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View Full Version : Car did something weird.....



fastsc92
08-29-2004, 04:15 PM
Last night I was coming home from the beach, getting on the highway. I was in 3rd gear, about 3500rpm. I went to merge into traffic so i put the pedal to the floor. The car fell on its face so bad and bogged down, then instantly there was a loud bang, like a backfire. I got off the gas right away as this all happening rather fast. The temp was good, oil pressure was good, boost and vac were good. And the air/fuel ratio was 14.5-15.3. I looked out the back while driving to see if it was headgaskets, but no steam, no smell, and the car didn't overheat, it stayed about 195deg in about 90 deg outside temps. The car acted normal the rest of the way home, and took some backroad ( the long way home) and kinda beat on it. The car pulled like a raped ape, and acted normal and a 12.1-12.4 air/fuel. I tried to get the car to do it again, but its fine. There is no oil in the coolant or vise versa, and no bubbles in the radator. I ruled out hg's.

I'm kinda baffled about this. I'm sure the car is fine, but it just makes me wonder. The car had about 1/4 tank of gas and the only thing i can think of is when i got on the long, sharp-turning on-ramp it sloshed the gas towards the drivers side of the car, and the baffle in the tank was dry, then when i went to get on it, it ran out of gas for a second, then when it received gas it backfired. This is just a therory, but its starting to make sense.

Any thoughts guys?

J.D.
08-29-2004, 06:09 PM
I thought that backfiring was caused by wrong spark timing, not fuel starvation.

fastsc92
08-29-2004, 06:12 PM
My thought was that it was adding a lot of spark, but there was no fuel to back it up at the time. Car acts normal now. Hmm...any more thoughts? :confused:

J.D.
08-29-2004, 06:33 PM
Looked up backfire in the dictionary: "Premature explosion in the cylinder of an internal combustion engine OR an explosive ignition of gases in the exhaust after the cylinder has misfired". So if there's no fuel there cannot be any explosion or backfire.

fastsc92
08-29-2004, 07:54 PM
I'm surprised Webster even lists that. Anyhow, If the timing is advanced just like it would under WOT, with no fuel, that could cause a backfire.....right?

David Neibert
08-29-2004, 08:16 PM
I would think you are more likely to get a backfire if the fuel keeps flowing and the ignition shuts off then quickly comes back on.

Kids used to make their cars backfire to scare someone on the sidewalk by turning the ignition off and then back on after a second or two (works best with manual trans). It sometimes blew the muffler right off the car.

That's probably why our rev limiter cuts the fuel instead of ignition.

David

fastsc92
08-29-2004, 08:56 PM
Makes sense Dave. Just still baffled as to what happened. Maybe the eec tuner cut out for a min? Who knows, runs good now. Cause it fell on its face almost like it was out of gas. Thats why i figured it might have been a loss of fuel, while the spark was advancing and the engine ran lean for a split second and then backfired. :confused:

XR7 Dave
08-29-2004, 08:58 PM
I would think you are more likely to get a backfire if the fuel keeps flowing and the ignition shuts off then quickly comes back on.

Kids used to make their cars backfire to scare someone on the sidewalk by turning the ignition off and then back on after a second or two (works best with manual trans). It sometimes blew the muffler right off the car.

That's probably why our rev limiter cuts the fuel instead of ignition.

David

Speaking of rev limiters, I have heard all kinds of bad things about a fuel cut rev limiter but I accidently had mine set at 5500 and hit it pretty hard a few times. It is actually very smooth. The car just flat falls on its face, no jerking, popping, or any other kind of scary stuff.

People worry about it going lean, but IMO, if it shuts fuel off completely, how is it going to go lean? The fire's going out. Period.