4AGZE ignition control issues

[mhiscott]

I've been driving my car for the past week or so with these issues, but it's a pain to drive and the erraticness of the ignition system is making tuning difficult. Here is the setup:

-MS-I v2.2
-MSnS-E 29q2
-MegaTune 2.25
-OEM CAS with 2 teeth filed
-MS ECU in center console, MS relay board in engine bay
-LM1815 + two vb921s outputting spark to two msd coilpacks

Anyhow, heres the issue. First of all, I'm getting tach spikes, mostly around 2200 rpm or so, but at higher rpms under throttle as well. The stutter at ~2000 rpm occurs even at next to no throttle. When the engine is shut off, the coils will intermittantly fire and megatune will show wierd things like the rpm being 83, or 2000 or whatever for a split second while the engine is actually off. This causes the fuel pump to kick in and the injectors to open for no apperent reason. So from that, it seems that there must be something whacky with the RPM input or the conditioning circuit. The LM1815 seems to have a good reputation however in comparison to other means of ignition control like the HEI4....
As far as grounds, my MS is grounded through the relay board to the frame rail in the engine bay, I have also grounded my LC-1's two signal grounds to this location. My other LC-1 heater ground has been grounded to a frame rail location about ~18 inches from the MS grounds. The NE negative signal from the CAS (which goes directly to the MS in the centre console) is grounded near the ECU by the centre console, and the vb921s are grounded directly to the MS pcb.
I was thinking of redoing the grounds in the following way. Have the head of the engine grounded to the frame rail with an 8 guage grounding cable, have the block grounded in the same way. Have the MS relay board ground (main ground for the MS) grounded to the intake manifold, as well as the 2 signal grounds from the LC-1, as well as the CAS negative pin. Basically, I'd route all my grounds to a single point on the intake manifold instead of different locations. If it matters at all, my battary is relocated to the trunk and is grounded to a rear strut tower with 4 guage wire. My main power wire is 4 guage from the battary in the trunk to the front of the car. Any ideas as to what could be causing this? I've got a dyno booked in another province for a week from now and if I don't figure this out by then it will be a wasted trip.

Thanks!
Mike

[jsmcortina]

The ground from your CAS needs to run right into the MS board. Either to one of the grounds on the DB37 or even better right onto the circuit board beside the LM1815.

James

[mhiscott]

Thanks, I'll try that, should I ground the sheilding of the cas wiring to the board as well or just ground that to my main ground point on the intake mani? The tin foily type stuff I mean around the 4 CAS wires.
-Mike

[lmr052]

The G- should go to the LM1815. The shielding can go to a general earth.

I would strongly recommend you either remove the G1/G2 pickups or put 220 ohm resistors across both G1 to G- and G2 to G-.

I have seen significant cross talk on the NE signal from the G1/G2 triggers because of the shared G- and perhaps because they are in the same shielded cable.

Regards, Richard