problems under boost! - Page 2

dean · 08-20-2006, 04:26 PM

So you have a wide band O2 meter? What does it do when the motor cuts out?

The vac retard unit on 930's depending on the year of the motor does nothing while boosting. If it is a later motor it might be a boost retard unit.

I would guess it is the fact that the plug wires keep falling off or a bad MSD box.

dean · 08-20-2006, 04:29 PM

Woops

What is the vacume at idle?

I would do a comp test on the motor. Sorry Chris. Ask Todd for more money

9dreizig · 08-20-2006, 04:38 PM

Dean, I"m feeding him lunches as fast as he can eat!!

9dreizig · 08-20-2006, 04:43 PM

Dean, the engine was running fine before the valve adjustment. I think the compression is probably pretty good. I'm assuming there is a vacuum retard on the distributor therefore it should have some effect right?

9dreizig · 08-20-2006, 04:45 PM

Oh Dean, the motor doesn't cut out just lunges/jerks, still continues to pull with full burst,, only it's kinda ugly.. A/F is 12.5 under boost 13.5 at idle.

dean · 08-20-2006, 05:32 PM

Quote:

Originally posted by 9dreizig
Dean, the engine was running fine before the valve adjustment. I think the compression is probably pretty good. I'm assuming there is a vacuum retard on the distributor therefore it should have some effect right?

The vacume retard, retards with vacume. So it makes no difference on boost.

If one plug isn't firing on a 930 it makes a HUGH difference in the way the motor runs. So I would focus on the plugs and the wires.

pjv911 · pjv911's Garage

Do you have another MSD box to try ? Could be cutting out under demand/boost .

Kurt Williams

9dreizig · 08-20-2006, 06:36 PM

Nope, just the one that came with the engine.
Why would it cut out under boost ??
T

pjv911 · pjv911's Garage

When cylinder pressures are higher there is more spark energy required to jump the plug gap. Possibly the MSD can no longer store and rebuild voltage fast enough to properly function. Closing the plug gaps to .016" or so as a test may show a difference. Im guessing you know the firing order is correct. You do know that cyl # 1 is the one closest to the distributor right ? Also if you using a shop manual for the wrong model year make sure to be aware that starting in 1978 the ignition rotor rotates the other direction.

Kurt Williams

9dreizig · 08-21-2006, 04:28 AM

Thanks Kurt, I"m putting new plugs in today.. We'll see if that makes a difference.
T

mark '87 930 · mark '87 930's Garage

see next post

mark '87 930 · mark '87 930's Garage

did you fix your problem? Mine does the same.. but when I disconnect the O2 sensor... she runs great.
When mine 'bucks" there is tons of black smoke going out the tail pipe... so I know it's not burning the fuel. Runs fine while not on boost though. I also know my plugs, wires, cap, rotor are all new (I know this because I changed them).

9dreizig · 09-21-2006, 05:27 PM

No it's still doing the same thing. I've been traveling on the west coast so have not had alot of time to work on it. Hopefully this week I'll get some time with it again..