Hoonigan Diagnoses C4 Corvette Misfire

Hang out with the Hoonigans as they diagnose this buget-friendly, barely-running C4 Corvette.

The Hoonigan Bonus Youtube channel has a video of particular interest to us. It features a long-dormant C4 Corvette project car, and the Hoonigan gang’s efforts to get it back on the road.

Hoonigan editor Kyle Stuart says, “We were thinking, like, engine swap and all these ideas, but…we just need to get it legal, first.” The car starts and runs well enough, but it likely won’t pass strict California emissions. Still, there are some promising signs. The air conditioning works, for example.

The first step is diagnosing the misfire issue, and Stuart’s co-conspirator, Vince Dan, gets to work. It’s pretty simple as the first cylinder seems to be the problem. After some additional testing, it’s determined that the plug wires are in good working order. That’s very good news, as anyone who has worked on these cars knows how difficult of a job it can be to replace them. With the distributor mounted behind the water pump, replacing spark plug wires is no fun at all.

Before replacing the spark plugs and having another go, the decision is made to drain the old fuel. It’s a smart choice, as, apparently, the car has been sitting for a few years. Anyone who has had to clean out their lawnmower carburetor in the spring will tell you that fuel breaks down as it sits, even for relatively short periods of time.

Unfortunately, one of the spark plug wires breaks in the process of changing the plugs. They do manage to get it back together, and the car does seem much healthier when it starts up with fresh gas and new plugs. There’s still a small misfire, but Vince advises that they let the car run for a little bit. “So when cars sit for a long time, say one of the intake valves is open, or one of the exhaust valves is open, they will develop rust on the face of the valve, and they won’t seat correctly.” He hopes that, by letting the engine run for a while, it will knock the rust off of and help the valves to seat better.

Unfortunately, that doesn’t fix the issue. After one more test – swapping fuel injectors – it’s clear that there is an internal engine issue causing the misfire. Vince explains his diagnostic process, and how he came to that conclusion. “When you’re looking for misfires, you’re looking for three things: either ignition, fuel – air/fuel ratio, or compression.”

Unfortunately, that means that this Corvette has an internal engine issue that can’t be handled in this video. However, Vince and Kyle were able to make some progress on the Corvette and get it one step closer to being back on the road.

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