Sputtering on boost...

[LTCol]

need help guys...

the car just started sputtering when hitting boost...normal acceleration is fine though... what could it be?

** i checked the coil wires for damage but i dont see any damage.
** i checked the plugs, its running 'Bosch +5 HR7DC' - not sure if this is the right plugs to run for my setup (previous owner installed it)
** could this be vac/boost leak?

thanks!

E30 M30B35 GT3582r topmount Tial 44mm wastegate Tial 50mm bov 3" straight exhaust

[Brad D.]

What is plug gap? What are you using for engine management and what is the air fuel ratio when the sputtering occurs?

[LTCol]

ill check the plug gap when i get to work, using MSPNP and af around 12-13 when sputtering occurs

[turbodan]

Plug gap, wires, cap or rotor are most likely. Wires aren't something you can check visually. They may not arc at idle either but under boost with a much denser mix in the combustion chamber they may be leaking. If you've never replaced them or its been a long time they are a possibility.

I was running around .024" on the gap I think. Not much but it didn't cause any driveability issues. It may have helped that I was running an MSD Blaster CDI instead of the stock inductive coil.

[Brad D.]

Plug gap, wires, cap or rotor are most likely. Wires aren't something you can check visually. They may not arc at idle either but under boost with a much denser mix in the combustion chamber they may be leaking. If you've never replaced them or its been a long time they are a possibility.

I was running around .024" on the gap I think. Not much but it didn't cause any driveability issues. It may have helped that I was running an MSD Blaster CDI instead of the stock inductive coil.

With the stock coil and cap/rotor I was running 0.025" with no problems up to 12 psi. Anything more and you may have problems depending on boost level. My feeling is that it is likely ignition related.

[marc79euro645]

I would suspect the vr signal might be dropping out. You should datalog it happening and study it. Tuning the two pots can help stabilize the vr signal, mega manual has a chapter on it.
good luck
marc

[EricF]

One lesson learned in the Volvo world is that there are a number of variables influencing the gap you can run at a given boost level. Even with a good baseline sometimes its difficult to open the gap up. And anything over a certain gap will blow out.

I have had cars that will run .025-6 easily, and those that I couldn't open past .023. The other thing to keep in mind is that copper plugs wear very quickly in boost. I used to re-gap every other oil change, and needed to.

[LTCol]

Thanks guys! found the culprit! 2 foul plugs and a small hole in the vacuum hose to the wastegate.

cheers! lets boost!