sync loss at startup

[Yves]

Was doing some fine tuning with regards to engine startup. Noticed a drop in rpm right after the engine fired and reached normal rpm, like it missed a beat and then picked up. The only thing that I see happening at that point is this is exactly the point that I let go of the key and the battery voltage goes back up again.

Is this some sort of noise or something else.

Msq and log attached.

[grom_e30]

its at the same point as you went from half sync to full sync

[Yves]

its at the same point as you went from half sync to full sync

didn't notice that. Thanks.
So this is camshaft sensor related. Any thing that can be done ? I use the halve moon type there.

[billr]

Try changing the "Check at tooth #" (presently is 0) in trigger/tooth settings.

[Yves]

See attached log.

It didn't want to start with it on 1.

[billr]

That 0 to 1 may be right at the edge of the cam "moon". Try some numbers quite a bit different, like 90, to try moving the interrogate moment way out into the on or off zone.

[Yves]

That 0 to 1 may be right at the edge of the cam "moon". Try some numbers quite a bit different, like 90, to try moving the interrogate moment way out into the on or off zone.

Just asking, but wouldn't that potentially screw up my ignition timing ?

[billr]

Maybe, depending on how close the cam wheel edge is to the present 0 setting. Maybe just that move to 1 degree put you in the wrong engine cycle phase. Use wasted-COP until you get this sorted out if you are worried. That will maintain ignition timing regardless of what the CMP is doing.

[Yves]

I'm unsure what to think of what happened. I remember setting these according the manual instructions for a toothed crank wheel and half moon type cam wheel. The instructions said something that the engine should have been set on the number one tooth and then the cam sensor should be at about 1/2 the relevant open/closed section of the half moon wheel. I remember that I had to turn back the engine to tooth 1 and then set the cam sensor so it was half way a half moon section, then measure what output I had. This was the way I did it. I set all the parameters as described in the manual and left the "0" setting as it was (untouched).
I would think that when the engine would be at tooth "0" the cam sensor should be half way on the half moon and so it should be on the edge of the half moon. I could do de facto check after som disassembly, but it just seems odd to me.

Thanks for helping.

[billr]

My perception is that detection in the "poll level" (half-moon) mode has changed at one point. Also, I think that "check at tooth#" is a fairly recent addition. I have posted before asking for clarification on some of this, but couldn't comprehend the answers so dropped my inquiry. Got it? I'm confused too, just trying to help you think it through.

[grom_e30]

post a comp log

[Yves]

My perception is that detection in the "poll level" (half-moon) mode has changed at one point. Also, I think that "check at tooth#" is a fairly recent addition. I have posted before asking for clarification on some of this, but couldn't comprehend the answers so dropped my inquiry. Got it? I'm confused too, just trying to help you think it through.

Ok, thanks Bill. Your help is appreciated. I don't understand it completly either.

[Yves]

post a comp log

Ok, will do so asap.

[Yves]

ha, I tried making logs today, but of course it doesn't want to do it again. Kinda strange. Only difference is that I charged the battery. Could this be involved somehow ?

[grom_e30]

my guess is that low battery was causing it to crank slower and the engine started before it saw cam sensor, you had the stumble as the ecu switched over to sequential after detecting the cam signal

[Yves]

my guess is that low battery was causing it to crank slower and the engine started before it saw cam sensor, you had the stumble as the ecu switched over to sequential after detecting the cam signal

Ok, so effectively nothing to worry about.

[grom_e30]

its nothing major. but if you post the comp log of the engine running you may get some advice on the best place to set you ecu to look for the cam sensor. it could be that the ecu is looking for it at a time where its harder to spot.

[Yves]

Attached the logs I made today.

[grom_e30]

comp log does not work for me

[Yves]

I hadn't checked, but apparently for me either Don't know why it didn't work. Will try to make a new one in the following days.