what went wrong?

[viper11]

hi
this is completely programmable by laptop with everything displayed and adjustable
my tune is very close but the autotune tweaks the fuel tables to match my preset a/f targets it is restricted to 5-10% max
everthing was going good then all of a sudden one cylinder went dead like a dead plug now I can't even start it
jason

[adynes]

I have the same computer on my car. I'm using 36# Bosch design III injectors, and I think they need a cleaning. The base tune was way too rich while trying to fire the engine for the first time, and the plugs fouled. The engine sounded much like the symptoms you describe. After changing the plugs and getting the fuel within range, it ran fine. Then, after adding spark control, I had similar problems, but I think this time the problem is a noisy tach signal, because when I disabled spark control (defaults to the base setting) it cleared up. I haven't messed with it since do to other work being done (paint, turbos, etc).

Have you checked the plugs yet? If that's not it, maybe check your ignition signal wiring for problems, or maybe the computer ground. Good luck.

[ohcbird]

Are you sure that you are 100% mechanically correct? Have you:

1. verified your timing order/plug wires
2. set base timing
3. verified your plug gaps & plug integrity
4. verified fuel pressure during all phases
5. Etc...

Given your 10% correction limit, did you see (or log) which way your WB was pushing? I'd do some solid fuel calculations before trying autotune. I agree w/Jody; I'm NOT a big fan of any autotune feature, as most of the time you'll get a real fat (rich) map. I definitiely wouldn't use it on my twin-turbo'd motor, as tuning for a specific A/FR doesn't do anything for driveability.

[viper11]

hi
since this I have narrowed my problem down, with the distributor removed and fuel pump fuse out I can hear the injectors clicking in time with the vr signal so my distributor vr signal is good
the problem is my spark is very intermittent, 1 out of every 3-4 injector pulses sometimes 7-8, I swapped coils and no difference so its either the ms or the msd6a or between the two.(remember it was running fine last year and earlier this week.
on the stim the ms performs flawlesly with the led's flashing and megatune confirms smooth operation
so how can i check the output signal from the ms to the msd??
how can I check the msd output??
jason

[viper11]

ok the tests and results so far
the msd performs flawlessly when the white wire is grounded(or ungrounded) even when i flick it as fast as possible,it has a nice fat spark at the spare plug.
the coil is good,(verified with a second coil).
the injectors click in time with me spinning my spare distributor, by hand plugged in with the fuel pump fuse out,(indicating the ms is receiving the vr signal) but the spark is very random and weak.
the ign on the stimulator works and flashes perfectly in sync with the rpm,
dwell is set to 50% fixed,
both pots are fully anti-clockwise.and tried2 and 4 turns clockwise
tsel to vroutinv.
sheilded vr wires. all wiring checked and was working fine
all grounds to engine block including msd.
was running and suddenly started by losing 1 cylinder spark.
is there anything I am missing?? if my vb921 was faulty would the stim work??
jason