Very rough idle, exhaust backfiring...
09-22-2006, 05:44 PM
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Car: 88 GTA Notchback
Engine: Edelbrock'd 5.7L TPI
Transmission: Stage 2 Trans go 700R4
Axle/Gears: 3.27 9 Bolt BW
Very rough idle, exhaust backfiring...
Well as the title says...engine is idling very rough, and backfires a lot.
Engine is a 350 with edelbrock TPI package on it, and performer aluminum heads. Car ran OK when I had my cast iron distributor gear on it but that got chewed up by the crane power max 2032 cam that has the steel gear on it...Replaced the gear with a bronze one and thats when all the problems started happening with backfiring and popping at idle and in gear.
I had the exhaust redone and sealed and checked so no apparant leaks in the exhaust. I have checked with a hose up to my ear and felt around the header/head and there was no buzzing of escaping exhaust gas (sound is kinda hard to describe but it buzzes sort of when theres a leak)
I have set the fuel pressure anywhere from 30psi to 55psi and it still backfires and pops. My O2 sensor readings constantly flip between rich and lean but generally lean out at idle, then a pop or backfire occurs then the computer dumps fuel in, and then it pops again because it just got dumped on, then it clears up a little bit. I do have a walboro 255lph fuel pump that makes a hissing noise through the fuel rails when it's priming.
I have current timing set to 8* BTDC, all new NGK iridium plugs, my old wires, checked the firing order and also replaced the ignition module.
The drivers side injectors tick noticeably and you can feel it, but on the pass side its really difficult to tell if they are ticking or not, but if you disconnect the injector harness off any one of them the engine stumbles. I cleaned the inside of the cap and rotor of the corrosion on the brass terminals which cleaned up the idle a lot.
Injectors have about 9000 miles on them, Accel 24#s and seem to be running OK.
I haven't checked the spark plugs yet though but will be doing that in the morning when it's cooled off.
Im wondering if anyone has any ideas of what else to check that would cause the rough idling and exhaust popping.
I dont have the neccessary tools to do a leak down test but im wondering if that might shed some light on what would be causing the lean/rich thing that's happening...
Any help is appreciated!
Engine is a 350 with edelbrock TPI package on it, and performer aluminum heads. Car ran OK when I had my cast iron distributor gear on it but that got chewed up by the crane power max 2032 cam that has the steel gear on it...Replaced the gear with a bronze one and thats when all the problems started happening with backfiring and popping at idle and in gear.
I had the exhaust redone and sealed and checked so no apparant leaks in the exhaust. I have checked with a hose up to my ear and felt around the header/head and there was no buzzing of escaping exhaust gas (sound is kinda hard to describe but it buzzes sort of when theres a leak)
I have set the fuel pressure anywhere from 30psi to 55psi and it still backfires and pops. My O2 sensor readings constantly flip between rich and lean but generally lean out at idle, then a pop or backfire occurs then the computer dumps fuel in, and then it pops again because it just got dumped on, then it clears up a little bit. I do have a walboro 255lph fuel pump that makes a hissing noise through the fuel rails when it's priming.
I have current timing set to 8* BTDC, all new NGK iridium plugs, my old wires, checked the firing order and also replaced the ignition module.
The drivers side injectors tick noticeably and you can feel it, but on the pass side its really difficult to tell if they are ticking or not, but if you disconnect the injector harness off any one of them the engine stumbles. I cleaned the inside of the cap and rotor of the corrosion on the brass terminals which cleaned up the idle a lot.
Injectors have about 9000 miles on them, Accel 24#s and seem to be running OK.
I haven't checked the spark plugs yet though but will be doing that in the morning when it's cooled off.
Im wondering if anyone has any ideas of what else to check that would cause the rough idling and exhaust popping.
I dont have the neccessary tools to do a leak down test but im wondering if that might shed some light on what would be causing the lean/rich thing that's happening...
Any help is appreciated!
09-23-2006, 09:58 AM
#2
When you installed the bronze distributor drive gear, did you check the axial play in the disributor shaft? Add or remove any shim washers? Check the interference of the reluctor and pickup coil?
The pickup coil poles should not be in contact with the moving pole piece (reluctor) and the topr of the reluctor should be at about the same level as the poles in the pickup coil can.
The pickup coil poles should not be in contact with the moving pole piece (reluctor) and the topr of the reluctor should be at about the same level as the poles in the pickup coil can.
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