Q: I missed a shift from 3d to 4th and over-revved the engine. There is now a misfire in every cylinder.

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Missed gear going into 3d and over revved engine and misfire every cylinder

My car has 157000 miles.
My car has a manual transmission.

Unfortunately, this could mean you have bent some valves. The best test for this is to put air pressure into each cylinder and see where it leaks from. You can utilize an expensive leak down tester or simply modify a compression tester to put around 50 psi of compressed air into each cylinder, one at a time. You will want to do either one with the the piston at top dead center. Sometimes you will need to hold the crankshaft by the crankshaft bolt to keep the piston from moving from TDC (Top Dead Center). TDC is important to make sure the valves are in their closed position. With the piston at TDC, compressed air in the cylinder, listen at the tail pipe, the intake manifold through the throttle body and remove the oil filler cap and listen in the crank case. You are listening for a significant rushing sound of air. If you here this at the exhaust, you have a bent exhaust valve, if you hear it at the intake, you have a bent intake valve, if you hear it from the crank case, you have a piston problem.

Most likely you will not have a piston problem. If you do, there will a lot of other problems besides a misfire. It is also possible the timing belt has slipped a tooth or two. While your checking for cylinder leakage, you can do a compression check in each cylinder. If you find some cylinders have very different results and the valves in the suspect cylinder are not leaking, it is likely the timing belt has skipped a tooth or two. The only other way to check the timing belt timing is to disassemble the front of the motor as you would in preparation to replace the timing belt.

It sounds like you were driving quite hard when this occurred. Somehow you have determined all the cylinders are missing as a result of the over revving, and if they are all missing, the most likely cause would be bent valves or camshaft timing. Hard driving can foul and damage spark plugs. So when you are doing compression and leak down tests, I would definitely take note of the condition of the spark plugs.

If you should need further assistance, I recommend having one of our mobile technicians come to your home to perform a misfire inspection and help you make the necessary repairs to your vehicle.

Good luck!

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