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MITCHL · 11-15-2002, 10:12 PM

I have an 87 GT with speed density, GT40 heads, Cobra Intake, 65mmThrottle body, Roller rockers, long tube headers, flowmasters, 3.55 gear. When I accelerate I get a heavy backfiring sound immediately after I have changed gear at low RPM's. It happens in second and third gear and sometimes in fourth. It's driving me crazy! My local speed shop says it could be (1) loss of vacuum pressure (2) O2 sensors are inoperative, or (3) Convert to Mass Air. I don't have much faith in my local shop because their first attempt to remedy the problem was to change my fuel pump to a larger one. $300 Canadian dollars later she's still Backfiring! Please help, what should I do? Is my engine in jeopardy because of this?

11-15-2002, 10:12 PM	#1
MITCHL Registered Member Join Date: Nov 2002 Location: Windsor/Canada Posts: 2	Backfiring Problems! I have an 87 GT with speed density, GT40 heads, Cobra Intake, 65mmThrottle body, Roller rockers, long tube headers, flowmasters, 3.55 gear. When I accelerate I get a heavy backfiring sound immediately after I have changed gear at low RPM's. It happens in second and third gear and sometimes in fourth. It's driving me crazy! My local speed shop says it could be (1) loss of vacuum pressure (2) O2 sensors are inoperative, or (3) Convert to Mass Air. I don't have much faith in my local shop because their first attempt to remedy the problem was to change my fuel pump to a larger one. $300 Canadian dollars later she's still Backfiring! Please help, what should I do? Is my engine in jeopardy because of this?