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Misfire

ThomasL

By ThomasL,
in General Automotive Discussion

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ThomasL Enthusiast

ThomasL

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Having some trouble after the engine rebuild. The engine misfires and won't rev over 5200 rpm.

The fuel mixture is very rich, about 10-10.5 A/F.

Any ideas what could be wrong? Something that can be easilly missed maybe?

www.gt-r.nu/specs.txt

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ThomasL Enthusiast

ThomasL

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Too hard to say with limited information, have you tried leaning it off? are you running standard boost? have you made many changes to the engine and accessories during the rebuild?...

Leaning it off how? At the moment I have no boost controller attached so it should be standard, but haven't got more than 0.4 bar I believe.

The engine has been bored 1 mm, the crank has been straightened and balanced, both the block and the head has been polished/leveled, new bearings, forged pistons, ARP rod bolts, oil cooler, blow off valve, Tomei metal gaskets and timing belt changed/added. Everything else from the list were before the rebuild.

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ThomasL Enthusiast

ThomasL

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Reason for misfire was an airleakage - a turbocharged car most common problem :+)

Nevertheless there is an issue with the airfuel value with very big variations of the afr value - even at idle (~ 11-17 ) . I do not know how the Blitz ECU handles it but on a Montronic there is a feedback of the lambdasignal resulting in variations between 14.5-15 with a periodtime of about one second. Lambdaregulation is on the Motronic active if rev is below approx 3000rpm and load is light (typically vacuum in the inlet) - and conditions above that its using preset values only but again Im not familiar with the function of the GTR/Blitz ecu so if anyone could fill me in I would appretiate it.

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