Car backfires extremely loud and idles rough **VIDEO**
#1
Staging Lane
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Car backfires extremely loud and idles rough **VIDEO**
So I'm completing the swap on my 68 Bird. The engine is a LQ9, stock never even taken apart. I've got headers on it, that are mated up to an exhaust that just has some mufflers and that's it! I also have FAST Fuel Rails on it. PCM is off a 4.8 2001 Silverado, the engine is a 6.0L 2003 Escalade.
Any idea what would cause the crazy loud backfire? Supposedly it shoots out flames I was told. It's as loud as gun shots. Not normal for sure... Do I need a tune when running headers and fuel rails? Otherwise fuel injectors stock. 255 fuel pump. 6AN fuel line.
PCM was bought from the company that made my wiring harness. I know that they removed the key immobilizer stuff off the PCM, programmed the tire size and rear end. Not sure if they did anything else.
I also have a P1336 code which I couldn't get done the other day with my friend's high end Snap On. It would just get stuck in the middle of the process..
Any idea what would cause the crazy loud backfire? Supposedly it shoots out flames I was told. It's as loud as gun shots. Not normal for sure... Do I need a tune when running headers and fuel rails? Otherwise fuel injectors stock. 255 fuel pump. 6AN fuel line.
PCM was bought from the company that made my wiring harness. I know that they removed the key immobilizer stuff off the PCM, programmed the tire size and rear end. Not sure if they did anything else.
I also have a P1336 code which I couldn't get done the other day with my friend's high end Snap On. It would just get stuck in the middle of the process..
Last edited by Seymor Butts; 06-29-2014 at 05:11 PM.
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Some more info...
It seems that it only backfires on the driver side exhaust (I do not have a cross over which is how I can tell). It literally shoots flames out the pipe. See video uploaded just now (note the whirring type sound you hear is the intake fuel pump):
It seems that it only backfires on the driver side exhaust (I do not have a cross over which is how I can tell). It literally shoots flames out the pipe. See video uploaded just now (note the whirring type sound you hear is the intake fuel pump):
#3
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Try some new plugs or swapping them from the other banks. also swapping the Coil pack from the other side.
could be a broken plug, wire or coil.. Those would be my suggestion.
Check the wiring connectors and harness of the coil packs. Have you also check the valve train ? Bent push rod or valve, check for broken spring ?
good luck with it. hopefully it will be something simple. I spend some time chasing my mis-fire / Backfire.. turned out to be a hair line crack in one plug.
BC
could be a broken plug, wire or coil.. Those would be my suggestion.
Check the wiring connectors and harness of the coil packs. Have you also check the valve train ? Bent push rod or valve, check for broken spring ?
good luck with it. hopefully it will be something simple. I spend some time chasing my mis-fire / Backfire.. turned out to be a hair line crack in one plug.
BC
#4
Almost certainly an exhaust leak. I once had a car with an exhaust air pump and a bad A/B valve. I use to purposely get on the gas then let off making it backfire in the Sepulveda tunnel under LAX. Every car in the tunnel would brake.
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Thanks all for the suggestions.. Looks like the wire harness for the driver side coilpacks was pooched. Luckily I had a spare sitting around, plugged it in and the car stopped backfiring. The idle is still a little crappy and I couldn't figure it out. It just sputters now when driving along - feel like its a timing issue now. I dropped the car off at a local shop to get it looked at for their opinion.