my car was fine all summer, if ever i hit boost cutoff i would need to just turn down my MBC.
now that its winter nomatter how low it goes i always seem to hit it.
i took off my MBC completly and it was fine ( it was also slow as hell)
i only hit it in 4th and 5th gear after pinning the gas for around 4-5 seconds.
i watch my boost guage at it hits around 9psi now ( its turned down) and for some reason i still hit it but the boost gauge never seems to actually go anywhere near 14psi when it cuts.
i was thinking
a. my boost gauge cannot detect the spike for some reason
b. it might not be the cutoff but a leak instead ( but it cuts for a second then is fine for another 4-5seconds)
c. a cheap boost controller
what do you think? thanks!

 

TCV maybe?

 

Maybe you are misfiring?

 

I've had oil soaked air box to turbo hoses collapse and feel just like a boost cut switch. Boost fine to a certain point; go past that point and boom...nothing.

 

thats funny you say that, last night i hit the "cutoff" 3-4 times this morning the car runs like trash..

ive changed the sparkplugs as well as the wires and cap/rotor before winter so hopefully all that stuff is good. what next?
im going to have to check my intercooler lines aswell. im going to go silicone soon enough. i was thinking about this aswell.

thanks

 

I just did all silicone lines a couple weeks ago, and believe me you will NOT regret that. my turbo holds boost better and boosts faster. it feels like i got a new turbo.

 

Did you buy good parts? Like the good Bosch cap and rotor?
Which wires did you get?
How much boost are you running?
What did you gap the spark plugs to?

 

bosch cap/rotor, kingsborne wires, spark plugs i dont remember, but im only running at 10psi..
but its like -6 to -15 degrees celcuis dont know if that changes anything!? maybe weakens the intercooler hose rubbers?

 

It doesn't matter how much boost you're running, plugs should still be gapped accordingly. .028. I would check them. Also, are you running a cheap MBC? That's probably not helping any.

And -15C is only like 5F. It's kind of hard to troubleshoot boosting issues when your boosting in that cold of temperature. Being that cold is going to **** with a lot of things. You just have to imagine how dense the air is at those temps. My friend has a stage III+ S70 and boosts completely normal, however, in really cold temps, he gets misfires, spikes, etc, and it's because it's so cold out.

 

so maybe its best to run no MBC in winter..

 

Nah, it's fine. Just turn it down maybe. Or don't do WOT runs all the time.

 

no, id rather run properly even if that means running no MBC..

 

matt01.......get a tune and you wont have to worry about it ever again.

 

My friend has the IPD Stage III Tune and still runs into this problem every Winter in extremely low temps. But if it's usually above freezing, he doesn't have any issues. Besides, beating on your car when it's that cold is a real easy way to bend a rod. I think I see at least one or two bent rod threads on VS every winter from people boosting too high during extreme temps.

 

Then he is not hitting fuel cut off and it something else. IPD removes fuel cut off from all their tunes.

 

Tech also brought up misfires, and maybe that's what he's getting.

Put in the BCS and see if it's still happening. If it is, it will help you narrow down where to start looking.

Wait, he said he took off his MBC and put the BCS back on and it was fine, why is this still going? lol. put the bcs back on, get a better MBC, and put it back on when it's not -150 degrees outside.

 

matt01, maybe you could explain what the cut off feels like.

I have felt both, the fuel cut off is an abrupt stall. The entire engine shuts off for a sec then runs again. A misfire is more of a jolt or popping noise/feel. Fuel cut off is obvious but misfires are scary and you think damaged something cuz its not a pretty sound.

 

its hard to explain really..

WOT its fine for a few seconds, all of a sudden my boost goes from 10 down to about 2 with like a noise like the engine suddenly stopped, not sure what the RPM gauge reads at this point, i normally look at the boost. it stays "down" for maybe half a second but i seem to lose so much momentum in that time. then the boost builds back up right away and im good to go for another few seconds if i keep my foot in it..

with no MBC it would never "cutoff" but i was only reaching about 7 psi max at that point..


x2 on getting a tune.. im looking for a good used one stage one for 4.4 manual..

 

That's because that's stock boost and you're not boosting high enough to hit cutoff. I bet you're misfiring and it sounds like your running a cheap MBC and that isn't helping. Also, check your gap. We asked before what your plugs were gaped to and you didn't know. You should know what they're gaped to and they should be .028, and then play with the gap from there depending on how the car is running.

 

even with the MBC im not boosting high enough for cutoff. i never boost near 14PSI..
but the gap is worth looking into.. ill check that. if i buy volvo plugs are they pre-gapped.. right now i have bosch or something..