M20 starting issue(SOLVED)

[F34R]

So my mother is having an issue with the m20b27(5spd) starting. It will turn over and everything, but sometimes it just does not want to start. Fuel pump and all lines are working, I am guessing a sensor? It will sometimes just die on the highway but you can turn off and turn back on then pop start every time. This weekend it has been starting and driving with no issues, but did it again this morning.

Also if you rev it sometimes it will cut right out and die. If you put load on it to speed up it will buck or kill out. It will crank and crank then catch then die out, crank some more then catch give it some gas and you can tell it is burning extra fuel after it starts. I am thinking maybe some little spark or sensor.

Spark plugs are good, so are wires.

Things I have done so far:
Plugs and wires
Checked fuel pump and lines
Pump relay and main relay were changed out for 100% known working.
All grounds, I did swap the engine over about 2 years ago. All the hose were cleaned and flushed clean with new clamps. So I am ruling vacuum leak out MAYBE. Who knows in 2 years.

I have no changed the coil or the cap, do the CPS go bad?

Is there a way to test the sensor on the AFM?

[Gregs///M]

So my mother is having an issue with the m20b27(5spd) starting. It will turn over and everything, but sometimes it just does not want to start. Fuel pump and all lines are working, I am guessing a sensor? It will sometimes just die on the highway but you can turn off and turn back on then pop start every time. This weekend it has been starting and driving with no issues, but did it again this morning.

Also if you rev it sometimes it will cut right out and die. If you put load on it to speed up it will buck or kill out. It will crank and crank then catch then die out, crank some more then catch give it some gas and you can tell it is burning extra fuel after it starts. I am thinking maybe some little spark or sensor.

Spark plugs are good, so are wires.

Things I have done so far:
Plugs and wires
Checked fuel pump and lines
Pump relay and main relay were changed out for 100% known working.
All grounds, I did swap the engine over about 2 years ago. All the hose were cleaned and flushed clean with new clamps. So I am ruling vacuum leak out MAYBE. Who knows in 2 years.

I have no changed the coil or the cap, do the CPS go bad?

Is there a way to test the sensor on the AFM?

You can test the sensor in the AFM only with a Oscilloscope. See my signature "services" section for what its signal feedback should look like.

[Killacortes]

I have had this issue on my 86 325es. My car did not have a CPS it had two reference sensors instead. Turned out my coil was bad. I would drive it and would die after sometime but after replacing the coil it ran great.

[F34R]

I have had this issue on my 86 325es. My car did not have a CPS it had two reference sensors instead. Turned out my coil was bad. I would drive it and would die after sometime but after replacing the coil it ran great.

That is my thoughts, I have not replaced that yet.

[yert315]

inspect your reference sensors as well.

[F34R]

Already did^ and it was the coil, that was the next thing on my list. Just had to get the spares from the shop. Thanks for the reminder Killa.