Q: Backfiring from throttle bodies when under load. 1984 Chevrolet Corvette

asked by on January 27, 2017

So the car was running fine one day. Next time I go to drive it, i hear a popping type noise coming from the engine bay. Sounds like a backfire coming out of the throttle bodies/intake. Car has the crossfire engine, a mild cam, hypereutectic pistons and bigger heads. Not sure of all the specs on it. Also has a hypertech chip installed in the computer. I say this because I did add an octane booster to it the night before this issue started happening but I did drive it that day and it ran fine. I pulled a valve cover, lost a washer in the head (oops), and had to pull off intake to get the washer from the lifter valley. While doing that, also had to pull out distributor. When putting the distributor back in, it would not line up correctly, as if it could only go one way. I am not Familiar with timing, I figured if the cap and rotor were inline as they were before it would be fine, even if the distributor itself was turned? I feel like I'm wrong on that now. Any advice?

My car has 161000 miles.
My car has an automatic transmission.

Hello - backfiring can be caused both by timing issues, as well as air leaks (unmetered air) into the intake. I would first have the timing set to be sure it is correct - since there is some reason to believe it may not be. If you still have backfiring, check for air leaks in the intake (starter fluid or smoke test metod). The Crossfire manifold system is complex enough for any of us to get right! For assistance, I recommend a backfiring inspection performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.

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Hello - backfiring can be caused both by timing issues, and by a leaking intake (un-metered air getting into the system. I would first get the timing set correctly, since this can be done without taking things back apart, and there is some question as to whether it’s correct now. The Crossfire intake is tricky enough for most any of us to install and seal properly. If you still have backfiring after getting the timing correct, I would test for leaks in the intake system (starter fluid or smoke test techniques). Worst case, remove and re-install the intake manifold to be sure there are no air leaks since this was the last engine maintenance. For assistance, I recommend an engine backfiring inspection performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.

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