M20B25: Tach Goes to Zero Engine Still Running

[Quinthirty]

Hi,

This happened to me twice already.

The first time happened a few days back. I was about to enter the freeway so I started accelerating when I noticed that the car bucked and the tach went to zero. The lights didn't go on, and I thought that the engine went dead but I could hear the engine running. But in the midst of it, I put it on neutral, switch off the engine, and re-start it on the fly. I shift to D and drive continuously to avoid an accident.

The second time happened today. In similar circumstances, I was accelerating when it bucked again, tach goes to zero, but this time I held the accelerator in place and didn't let go. I noticed that the engine was like on limp mode not wanting to rev, and it was still running. After a few seconds, power kicks back in and it drives normally.

What should I check, gents? Fuel pump? Dirty fuel tank? I have a refurb AFM, and coil.

Thanks r3v.

[AwakenNoMore]

check your crank position sensor and the connection for it. Had this same issue.

[jlevie]

Yep, sounds like a loss of timing data to the DME (bad CPS or engine harness) or a bad DME.

[Quinthirty]

Thanks. I will check this.