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NK 6G74 DOHC missing butterfly....

Posted: Wed Feb 24, 2010 5:41 pm
by selaga
Took the Paj for a 130K service, took the manifold off to replace the plugs and check the coils, and then I look into the inlet manifold and there is one butterfly missing (5X) ? Look into the lower manifold and it is not there, strange ??? One owner before me, car is running sweet apart from the leak at the front bush at the manifold.....

Has anyone removed the shaft and butterflies and welded up the front hole ? Haven't rang dealer as yet, but my guess is the manifold will be pushing $1000......

Any insight/info/advice is greatly appreciated.

Cheers,

Posted: Thu Feb 25, 2010 11:14 pm
by scooby_74
The whole design of having the butterflys is to create a smoth idle and lower end torque.
When the engine gets higher in the revs it opens to allow maximum air flow in as straight a line to the engine as possible allowing top end power.

I know if the butterfly is held open the vehicle lacks light thortle drivability, but is not too bad, fuel economy apparently does suffer a little as the air flowing into the engine is not smoth.

Posted: Fri Feb 26, 2010 4:16 pm
by steverisingsun
scooby_74 wrote:The whole design of having the butterflys is to create a smoth idle and lower end torque.
When the engine gets higher in the revs it opens to allow maximum air flow in as straight a line to the engine as possible allowing top end power.

I know if the butterfly is held open the vehicle lacks light thortle drivability, but is not too bad, fuel economy apparently does suffer a little as the air flowing into the engine is not smoth.

I have had these things rattle off and sit over the valves, so take care!

Posted: Fri Feb 26, 2010 5:29 pm
by Bitsamissin
Yeah a lot of the US guys remove them completely and report that they still drive ok. Others have made up a much better bushing arrangement for the shaft. There have been a few instances of them falling off and causing major damage.
I think the 3.5 SOHC had a different design to address this issue ?

Posted: Wed Mar 03, 2010 1:56 pm
by selaga
Guys thanks for your input...

I picked up the car today from mechanics, I drilled out the first two steps where the shaft goes (left the last step so that welsh plug can rest against it) to M12, then put in a bit of Loctite and a M12 welsh plug.

Assembled it all back together and took it for a drive.

My initial observation is that below 2500 it has lost some of the torque, and the top end is as good as before....Not really an issue, as torque converter stall masks it, it would probably be more noticable in a manual.

I didn't notice any effect on the idle, it is a smooth as before......

Would I do it again, this way, or spend $800 for a new lower manifold ? I would do it all over again, small loss for a big piece of mind (not chancing other screws/butterflies coming off)....

If someone need any spare butterflies (X5), let me know........