New engine boost issue

rustfarmer

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Hi everyone, finally got my fresh 7M GTE running and at first all seemed well. Cranked with fuel disabled to build oil pressure, then fired right up. 1st test drive seemed good until I decided to do some WOT runs from 30MPH in 3rd gear up to about 60 or 65 MPH. First few runs were good, but 4th or so had a sharp stumble at mid rpm then climbed normally. Further testing shows issue getting worse, and runs poorly as soon as I get to 5 pounds of boost at any rpm in any gears. During 1st several runs I noticed boost would build to 10 lbs rather easily. Car has driftmotion 3" exhaust and downpipe, stock turbo and wastegate, greedy BOV, aftermarket intercooler and pipes. Car sat for 2 years during build, but I think I had added sta-bil to fuel and it smelled OK. Would bad gas trashing injectors or fuel filter act like this? Don't think it is ignition, but perhaps stock AFM is causing issues. Did not have this problem before build (done for spun rod bearing). Any help most welcome.
 

rustfarmer

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More information. When turbo was rebuilt I don't think anything was done to the wastegate so it is a stock 25+ year old unit. Perhaps the spring slowly gave way and now is broken. Could this cause my problem?
 

hvyman

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Drain the gas and put fresh gas

And check all inter cooler connections
 

rustfarmer

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One more part of the puzzle, noticed when we first ran it that under fair throttle it was showing 10 more lbs of boost. This also makes me think the wastegate may be faulty.
 

suprahero

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Double check all intercooler pipes like mentioned above.
 

hvyman

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Stock wastegate not known for going bad although it could happen usually it would fail in the not holding boost. But if the hose to the wastegate was missing or fracked that could cause a over boost and you would hit fuel cut.

Also bad hose or clamp from the air flow meter to tb could cause exactly what your describing
 

rustfarmer

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FIXED. Hose clamp missing on lower intercooler line and hose had worked itself almost all the way off. Now runs strong and pushes 11 to 12 lbs of boost then hits fuel cut. Should stock wastegate allow this?
 

Supraflymk3

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With an upgraded exhaust and intercooler your engine breathes better which in turn you'll get a few extra pounds of boost over stock which is normal. Typically fuelcut can happen anywhere from 12 to 15 psi.
 

suprarx7nut

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It's not normal to hit fuel cut without a boost controller in my experience. Are you hitting 12 PSI without a boost controller?
 

rustfarmer

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It's not normal to hit fuel cut without a boost controller in my experience. Are you hitting 12 PSI without a boost controller?
Yes, it hits 12 psi at about 5K rpms. I know many go fast folks would say "great, just do all the fuel system upgrades and enjoy" but just not in my buget right now.
 
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rustfarmer

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Looks as if the new IC pipe was hitting the wastegate linkage and preventing it from operating. Still get 10 to 11 psi at full revs (guessing since I have not done the tach fix yet, but resistors are on order) and not hitting fuel cut so I think it is FIXED
 

suprarx7nut

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Nice, good news. Thanks for the update. I didn't think the stock CT could hit fuel cut without a failure or modification and this is a data point in favor of that train of thought.