I have a 1986 Toyota MR2 4AGE NA. I replaced the plugs, wires, distributor cap, and rotor button a few weeks ago and, until yesterday, have been enjoying excellent performance and gas mileage.
Yesterday afternoon near the end of a 25-mile drive, I heard a knock coming from the engine. It sounded a little like a rod bearing, but it only occurred when I loaded the engine (accelerating or going up hill). The sound disappeared at idle or while coasting. I also noted a corresponding significant loss of power.
Attempting to isolate the problem to a cylinder, I disconnected the plug wires from the distributor one at a time. Disconnecting any wire resulted in the car stalling, except when I disconnected #2, which ceased the knocking and brought a slight but perceptible increase in power.
I have spark to the #2 wire and, though I haven't checked the plug itself yet, I suspect it's firing because disconnecting it causes a change in sound and performance. So that narrows it down to fuel (bad injector?) or compression (bad valve?). The knocking (some kind of internal backfire?) makes me suspect a valve problem. Does that make sense to anyone else? Anyone seen this before?
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