1G CAS and Random misfire and CAS inaccuracy

[aero_sallee]

So I was having trouble today with getting megasquirt to sync and pick up an RPM signal. Took apart the CAS to test it, found it had gotten wet and not getting a CAM signal out of it.

In the process of trying to figure out the issue, I think I observed at least part of the issue that causes the random misfire codes to pop up. At first I thought maybe something was wrong with the CAS or cam slot, but I tested two separate heads and cam sensors like this I got the exact same amount of play while eyeballing it.

I'm not sure if the play is in the pin in the shaft or in the slot, but I would guess a bit of both.

Here is a video I took with my phone of the play.

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I'm not sure what would be different with the black top cas that would help prevent it, but I know the 97+ CAS threads into the end of the cam and would help eliminate the play.


Just something I didn't expect to see and had never had the cover off while it was mounted before. Even if its only a degree or two on the head, double that at the crank and I can see it causing issues with the random misfire detection.

Seems like there would be some way to help tighten things up a bit for someone willing to do a bit of work.

 

[turboglenn]

all the CAS sensors do that bit oif wiggling. It apears as though you're running a 6 bolt swap in a 2g car. There's some explantion to that CEL on RRE's website on their write up of the swap and some way to use a potentiometer to eliminate the random misfire CEL.

Personally i love the slotted optical CAS nad hchanged to one from the black top hall effect because i was getting bad misfires from EMF interference or something and even had random RPM readins on a WOT pull (like back tracking a couple hunred to 1000 RPM then jumping back up to where it should be) and the green top hasn't shown that in a single log yet so i'm happy with that

I would say check the RRE thing first (sorry no link) and then look else where because the case is probably fin as long as you get an RPM reading when cranking (the home sensor isn't reall even needed but is usually hooked up on batch fire EMS installs)

 

[aero_sallee]

all the CAS sensors do that bit oif wiggling. It apears as though you're running a 6 bolt swap in a 2g car. There's some explantion to that CEL on RRE's website on their write up of the swap and some way to use a potentiometer to eliminate the random misfire CEL.

Personally i love the slotted optical CAS nad hchanged to one from the black top hall effect because i was getting bad misfires from EMF interference or something and even had random RPM readins on a WOT pull (like back tracking a couple hunred to 1000 RPM then jumping back up to where it should be) and the green top hasn't shown that in a single log yet so i'm happy with that

I would say check the RRE thing first (sorry no link) and then look else where because the case is probably fin as long as you get an RPM reading when cranking (the home sensor isn't reall even needed but is usually hooked up on batch fire EMS installs)

I don't have the random miss code problem since I'm not running a stock ECU. Running MS actually. This was more an observation as to the possible causes of the ECU picking that up. The car isn't actually missing in those cases, it just senses what it thinks is minute changes in crankshaft speed and throws the code. What I'm observing with this play, could easily be picked up as that variation in "crank" speed, especially when combined with timing belt slop etc. Although since the black top CAS helps people avoid it I would lean to something in the sensor, rather than just timing belt slop. I would love to see the top removed off a black top CAS and see if it has the same amount of play in it.

I did have the problem on another car, the potentiometer on the baro wire from the maf just prevents the ecu from looking for the random miss since it sees things are out of spec. Have to retune for that too, since it throws off the AFRs when tweaking it.


I don't recall anymore what standalone are you using?

Just thought it would be interesting to see what people thought.

 

[turboglenn]

ok, i got ya and what you're talking about, sorry i was thining you were talking about a stock ECU with ECMlink or something.

i'm running a haltech E6X (got it instead of the platinum series because i like simplicity, plus the dual mapping feature is easy to setup and use)