Thread: Boost Issue
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Dave 86 930 Fl Dave 86 930 Fl is offline
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Join Date: Dec 2005
Location: 1000 Islands NY
Posts: 405
Boost Issue

Iím experiencing an issue where the engine hesitates/stumbles/misses under boost.

This all started when I overfilled the oil during an oil change. Prior to the overfill, the car ran 13.5 afr off boost and high 11ís on full boost and the car ran like a scalded dog. Ever since the overfill, the car runs rich around 10.3 afr off boost and when the stumbling begins, it briefly runs lean (14+) before I get off the gas. Iím curious as to why the off boost afr mixtures became rich after the overfill, but I suspect that the overfill may have caused the problem. I became aware of the overfill issue at the track when the engine started stumbling and a bunch of smoke blew out the exhaust, so I drained some oil off to get the correct oil level. I checked the air box and I had sucked some oil up and it obviously entered the intake past the metering plate. I cleaned up the metering plate, but Iím thinking that any oil on the mechanism may be adding weight to the plate and as a result, the engine is running very rich. If this is true, would an overly rich condition cause the car to stumble on boost? If the problem is the oil residue on the metering plate, what is the best way to clean it?

BTW, the car is an 86 930 with stock internals, K27-7200, AI fuel head, Andial intercooler, .9 bar, B&B headers. I recently had the motor out of the car in order to replace the head studs and everything looked very good Ö pistons, bearings, cylinders, etc.

Regards, Dave
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1986 930 - K27-7200, Andial Intercooler, Tial Wastegate, Electronic Boost Controller, B&B headers, Bodart Zork, Leask Adjustable WUR, Full Elephant Racing Suspension w/Adustable Spring Plates and Von Shocks, Wevo Transmission Mounts, Fuel Safe Fuel Cell, Forgelines (9"/11"), Hargett Shifter, Innovate AFR, Cobra CF Seats, DAS Rollbar, Coleman Floating Rotors, Lightweight Interior, Forgeline 17" x 9"/11", 2800 lbs.
Old 10-27-2008, 03:18 AM
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