Car still misses

[mb911]

Ok here is what I have done.

81 sc engine
checked fuel pressures all are good
timing is perfect
rebuilt distributor (igintion)
new wires
new plugs
new green signal wire
compression 165 all cylinders cold

Could it be?
brain box?
Fuel distributor
wur??

again all fuel pressure were right on for an 81

Please help before I pull out a shotgun!!!!!! And start blasting hole in the side of the car

[mb911]

souk? anybody?? I am going to load the shot gun

[Gunter]

Sounds like fuel related. Misses at idle? Low RPM? Any RPM?
Mix setting at 3-3.5% OX?
Freq. valve is working?
Check spray pattern of injectors?
Small vacuum leak?
CDI module can fail intermittendly, not just completely.
Can you borrow a Bosch CDI module from someone?

[SC-targa]

I'm having the same problem with my 82, but I've just set the car aside for a while and worked on other things. Can you describe the miss? Doe sit occur at part throttle, full throttle steady state cruise or at idle? Does the car start well and idle?

You didn't mention checking the coil. I assume that you hear a whine from your CDI box when the ignition is on.

I don't think this is it, but do your injectors have a nice spray pattern? Does you fuel pump make enough pressure? How old is your fuel filter?

Good Luck,

Jerry Kroeger

[IROC]

Just a wild guess, but how about the CD box? I know the typical failure mode is *complete* failure, but...

You say "all pressures were right". I assume that means the control pressure responded correctly as the engine warmed up? (eliminating, most likely, the WUR).

Sorry I can't do more than offer some random guesses and sympathy...

Mike

[mb911]

Thanks guys
I have msd ignition new box and coil
Fuel pressures and good through the whole range check several times. Co I am sure is off as I have checked this then messed without the proper tools.

The car starts and idles perfect so it is part throttle that I experience this at ;and it is not noticable WOT but that does not mean its not doing it.

Fuel filter Is 3000 miles old, Patern was checked 3000 miles ago but I should probably recheck. I also will check to see what type of voltage I am getting to the ignition box when running at break today

Please keep rolling with input

[mb911]

just checked voltage its 13.5 so we are good there

[IROC]

Time to shoot it. :>)

Mike

[Eric Mckenna]

Did ya try the cap and rotor?
not that it IS that but, I didn't see it on the list of things you have repaced..


-Eric

[911mot]

Inspect cap for cracks/tracking marks

[Mike Andrew]

Well, I'm glad that I haven't ordered the signal wire yet. I'll just follow this thread for awhile.
Seems to be a common SC problem, though. I would think somebody here has it figured out & knows the proper fix.

[mb911]

just drove it it runs ok wot but misses every where else. ANyone want a free 911?? It mi9sses rich it misses lean so whats up?? Does the brain just not work properly?? o2 senser?? Or should I just junk it?

[mb911]

see my new post with the answers to the question

[mb911]

Finally found the issue. While working with my dizzy on a dizzy machine we found that the distributor would advance over its spec by as much as 5 degrees at any given rpm. So we are currently adjusting the dizzy and will final run tonight. We are also going to be offering this service in the near future as we feel there probably are a bunch of dizzy's out there with the same problem

[sammyg2]

My guess is that it has something to do with the mechanical advance on the dizzy coming in too soon. check the springs

[mb911]

Yeah that's what I said! Not trying to be mean but Thats what I tried to say. We are tweaking the tangs accordingly