930 Stumbling When Warm

[RarlyL8]

I don't think the WUR is your problem but it is real easy to find out, simply replace it with another one. You may benefit from an adjustable unit depending on what power level you have. Map the AFRs and see where the line can be straightened out. More torque better fuel mileage less cylinder washing.
What specific function of the fuel head or WUR are you wanting to look at as the possible culprit?

[Adam144]

Thanks for all the links and suggestions guys. I have some reading to do.

Originally Posted by RarlyL8

I don't think the WUR is your problem but it is real easy to find out, simply replace it with another one. You may benefit from an adjustable unit depending on what power level you have. Map the AFRs and see where the line can be straightened out. More torque better fuel mileage less cylinder washing.
What specific function of the fuel head or WUR are you wanting to look at as the possible culprit?

I can't understand what other items regulate fuel flow that would cause such an issue? There are 4 fuel pumps so it's not likely that. It isn't spark. We've trouble shooter everything else, the thing holds enough boost to hit almost 1.5 bar on the tell tale gauge so I doubt a boost leak.

[RarlyL8]

the thing holds enough boost to hit almost 1.5 bar on the tell tale gauge so I doubt a boost leak.

This alone will shut down your engine via the overboost switch, if it is still wired OEM.
Why 4 fuel pumps? Are any of these pumps wired in OEM to the overboost switch?

[gsxrken]

Originally Posted by Adam144

- The stumbling isn't just when on boost. The car stumbles and runs rough even down at idle once the issue starts happening.

Electrical components on their last legs usually exhibit issues first only when hot.
Since your fuel system is seemingly redundant (I won't recommend a 5th pump ), it has to still be ignition. MSD boxes are known to flake out in weird ways, and usually when hot. New coils are sometimes bad. Grounds, at the negative cable to body, and the copper one to transaxle should be wire brushed and snugged up.
Good luck.

[Steve Hummel]

Adam, you have a pm

Steve

[Adam144]

Originally Posted by RarlyL8

This alone will shut down your engine via the overboost switch, if it is still wired OEM.
Why 4 fuel pumps? Are any of these pumps wired in OEM to the overboost switch?

I should clarify that statement. The car has a boost controller and had a 1.0 bar spring. The controller allowed the car to make 1.5 bar. So the spring was swapped to a 0.6 and it now pulls only 1 bar. Was simply clarifying that if it were a boost leak I doubt it would've held such steady pressure. It's all new silicone hose as well.

I addressed the 4 pumps earlier in the thread. It has 2 Holley pumps that pump fuel from the ATL fuel cell to an accumulator of sorts and then the two factory pumps do the work from there. Actually the factory rear pump wasn't hooked up and we thought maybe that was part of the problem but it made no difference.

[Adam144]

Originally Posted by gsxrken

Electrical components on their last legs usually exhibit issues first only when hot.
Since your fuel system is seemingly redundant (I won't recommend a 5th pump ), it has to still be ignition. MSD boxes are known to flake out in weird ways, and usually when hot. New coils are sometimes bad. Grounds, at the negative cable to body, and the copper one to transaxle should be wire brushed and snugged up.
Good luck.

I will double check all the grounds and clean them up. The MSD 6-AL is mounted inside the car on the rear firewall. I don't think it gets very hot in there and from what I've been told by a Porsche mechanic who is also an electrical engineer is that they either work or don't work.

I really doubt the coil as I said it had the problem with the slightly used blaster coil and again with a brand new one.

It really feels like a fuel starvation when. Being driven. Like its running out of gas. That's why the focus is on fuel delivery. It doesn't sound or feel like a misfire.

[RarlyL8]

What is your system pressure and warm control pressure when the engine is running well and also when during malfunction?

[Adam144]

Originally Posted by RarlyL8

What is your system pressure and warm control pressure when the engine is running well and also when during malfunction?

The gauge from Pelican just arrived in the mail yesterday. I will post results when I have them.

[550SPYDER]

Adam144, I am having the same issue with my 83 930 and have the same setup you do regarding MSD, Blaster - can you update on what your solution was? Thanks in advance.