Thread: help diagnose engine dying

I tried to narrow it down, although I didn't have an oscilloscope to hook up. I couldn't get it to stumble or die idling or driving normally, but if I rev the engine up to 4,000 RPM it would start to cut out like a rev limiter. But I don't think the PCM will rev limit at 4,000 RPM even in neutral. I put it in first gear and floored it and would get cutouts that were sharply on-and-off, not at all like a fuel pump getting weak which in my experience is more like running into a pillow as engine power falls off. Also I had my son sit in the back with his ear to the pump. There wasn't an audible indication the fuel pump was having trouble.

So I do think the CKP (service manual term) is a likely candidate. Service manual also shows it is a PITA to replace, requiring one pull and re-install the harmonic balancer. And if one pulls it, it should probably be replaced with a new unit as the rubber often fails with age. And belts. Maybe the tensioner too. Guess I should change the water pump while I'm in there . . .

I'm thinking I should be absolutely sure it is the crank position sensor first, given the work and expense involved. I was thinking of bringing an oscilloscope home from work and probing the 3X and 18X signals while revving the engine to 4K. I don't suppose there is an easier way to confirm the failure.

Originally Posted by Lifespeed

I tried to narrow it down, although I didn't have an oscilloscope to hook up. I couldn't get it to stumble or die idling or driving normally, but if I rev the engine up to 4,000 RPM.

This is because there is a rev limiter at 4k to keep you from over reving it and blowing it. The limiter is increased when in gear.. but there's still limiters

Originally Posted by BillBoost37

This is because there is a rev limiter at 4k to keep you from over reving it and blowing it. The limiter is increased when in gear.. but there's still limiters

Is there anything I can do to confirm the cause of the problem before spending time and money on this repair? It doesn't appear to reproduce on demand, but I know if I my son takes it out driving around it will leave him stranded.