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Cutting out under low boost

PNW760

Member
Joined
Jul 8, 2015
Location
St. Louis, MO
I?m having an issue with my 93 940 turbo where it?s cutting out almost where it feels like fuel cut or a fuel pump that just ran out of gas and struggling to die when under lower boost. I don?t have a manual boost controller setup so I normally hit 7-8psi stock based on my boost gauge I have set up. Under 6-7 and I?ve had it occur also around 4psi on the freeway where it will cut out as I?m attempting to speed up (3/4 throttle to full throttle), it bucks and stops building boost pressure. As soon as I let off, it goes back to normal. I can cruise to highway speeds and have no problem driving, just under acceration under those conditions...

I?m at a loss as I have a full tank so I?m not running the fuel pump dry or something, pumps are both under 10,000 miles new, no performance exhaust or anything crazy. Only big modifications are an Mitsubishi Evo 8 all aluminum intercooler and due to sizing and spacing, I had to remove the stock airbox and fit a cone filter to work with the hoses that go to the intercooler inlet.

Any ideas?
 
Are you able to monitor the AFR's while this is happening?

to verify fuel pressure tape a test gauge to the windshield and test drive.

You may (probably have 2 pumps), a feed pump in the tank and a high pressure pump.
 
After driving it more tonight, it's begun to misfire under any amount of boost. Needle for boost pressure stays constant so I don't think it's vacuum related, either fuel or electrical.

I can't get it to go past 3000 rpm freeway driving or on the street at low speeds.

Could it be my Fuel Pressure regulator?

I just replaced my cap and rotor so I have no reason to suspect those...I think..
 
Air cone directly onto the MAF?
This seems to be a problem sometimes.
A cut off or slow down? Slow down will be the sucked pipe between MAF and Turbo.
Check the sparks and gap. Which spark? Brand and heat range?
Not enough informations from you about the car, sorry.
Good luck, Kay
 
You need 90 degree bend in hose before AMM like stock also make sure your pre turbo air hose isn't collapsing from the sucking of the air in. THat is a common problem also. It clamps shut and then your motor bucks.

The bucking description makes me think collapsing intake hose.
 
I might have a 90? bend of aluminum that I can put on before the AMM. Also will try to find a known working AMM and see if it makes a difference.

Just changed plugs and all 4 were extremely fouled and all white. Let it run a bit and it still seems to misfire with new plugs but will go for a drive here shortly to confirm.

Sbabbs: I’m running a DO88/iPD pre-turbo air hose and it’s strong new silicone so I don’t think it’s collapsing..
 
To reword that, that is the hose coming off the AMM going into the turbo, NOT the intake side, coming off intercooler going to the intake manifold
 
It sounds like a misfire complaint....

I would do a smoke test for air leaks and throw cap, rotor, Bouigcord wires, and properly gapped NGK copper BPR6ES plugs at it.
 
Cap and rotor were done literally just last weekend with bosch units, it currently has good looking bougicords, and I just installed a set of NGK BP7ES’s gapped to 0.028 an hour ago. Got in to drive it and it was misfiring at idle. Previous plugs were all fouled terribly. I’m thinking it might be MAF/AMM as mentioned above.

I just left for class so I can’t text it now but I think I have a good one at home I will try once I get back
 
It could also be a misfuel based misfire or a mechanical. So it did this right after you were in there...?
 
In my stupidity setting up the cone filter, I wrapped a whole bunch of electrical tape around the MAF to ensure a snug fit from the semi loose cone filter. What I didn't take into account was the heat that would cause the crappy electrical tape to lose adhesion and slide...and slide covering half the MAF screen...

47415656742_d62ec9c550_z.jpg
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Secondly, As I was looking, i caught this plug wire arcing on Cylinder #1... This could have been to improper installation as I didn't notice it last night while i was checking but I'm assuming that this is the other reason it's misfiring...

IMG_0934[/IMG]

Gonna stop by IPD tomorrow and grab some new wires, should I do their performance wires or Bougicords?

MAF looks okay so I'm going to attemp to fit the stock airbox back in...if not, a 90 degree bend after the MAF will definitely be done.
 
Well airbox won't go in with the Evo 8 intercooler so I might have to end up running a cone filter, but the cone filter won't fit around the 90 degree pipe... the opening in the air filter is too big, and I really don't want to do electrical tape again...
 
Try the stock box if you got it and it fits still. Or what does fit the AMM intake is other turbo boost hoses. Cut a piece of that to make an adapter or use that as your intake 90. I do and I put a piece of exhaust pipe in it to keep it from collapsing. Let me look for a pic.

conefilter.jpg
 
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