Early 944 Temp Sensor Issues

[Tom]

Any chance the scope settings are missing every other pulse? Have another 4 cylinder car around you could use to confirm your set up?

[delgadostarside]

That's a great idea, I actually daily a 94 camry and shes a 4 cylinder too! Perfect. Same type of ignition setup as well with the coil and mechanical distributor. I couldn't figure out the trig setting on this scope & i'm not sure i can actually just select a trig voltage so i'm using a power supply on another channel to set the trigger level in the video. I'll try that out in the morning, Thankyou!

[Tom]

You might also pull one spark plug wire at a time while the engine is running, just to confirm that all four are actually firing.

[Tom]

That's a great idea, I actually daily a 94 camry and shes a 4 cylinder too! Perfect. Same type of ignition setup as well with the coil and mechanical distributor. I couldn't figure out the trig setting on this scope & i'm not sure i can actually just select a trig voltage so i'm using a power supply on another channel to set the trigger level in the video. I'll try that out in the morning, Thankyou!

Worth trying, although it wouldn't explain why the tack also reads low...?

[delgadostarside]

Well, it would at least confirm if the oscilloscope setup is reading right.. If it isnt the oscope, i'd have to attribute it to something else causing the half firings. I'll try out the pulling plugs too with the oscope on it and see any changes as well. The thing is, the tach matches what the scope is getting so it has to be working right and thats what concerns me, almost like the dme isnt firing the coil right.

[Tom]

Any chance the tach is right?

[delgadostarside]

right relative to engine speed or the pulses? by the pulses it matches it seems, but engine speed, no way. That idle in the video is definitely not 500rpm, and when i rev it up high it never goes above`1200 rpm on the tach and its definitely way above 1200 rpm when ive revved it high. At the end of the video when i rev it, it shows a little less than 30 Ms which would coincide with ~1000 rpm but its definitely way higher than that in actuality.

[Tom]

If the other car gives you expected pulses, maybe turn off triggering on the 944 to see if maybe every other pulse looks different? Sharp enough to create a spark, but not sharp enough to trigger the scope or tach. Kind of grasping at straws here

[944er]

I get 50 mS between pulses looking carefully (i.e. frame by frame) at the beginning of your video, so an idle speed of 600 rpm. On cold start, my tach reads 625, and the engine sounds just like yours. I don't think your scope is deceiving you.

[delgadostarside]

I get 50 mS between pulses looking carefully (i.e. frame by frame) at the beginning of your video, so an idle speed of 600 rpm. On cold start, my tach reads 625, and the engine sounds just like yours. I don't think your scope is deceiving you.

The thing is, this is after warming up just under op. temp. Another thing, in the video i rev it up pretty good till you can here it breaking up a bit in the end. At that point the tachometer reads around 1100-1200 only as well and never goes past that ever. I'd prefer not to redline her but i've gotten it up probably 1k under redline with the tach still reading around 1200 only so i don't think it is right at all. I want to confirm this using a different test method, i bought one of those laser tachometer readers with the reflective tape. Thing is, lately it's been so cold here in New York no matter what i adjust i cant even get the car to fire once at all. Might have to wait till the spring now, really a bummer. I also keep forgetting to test against my camry ignition coil I'll try that one out tomorrow as well as the laser tachometer on it since that at least runs