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'99 996 cab tip: misfire & stalling - *valve problem!*


slknv
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5 hours ago, Zelrik911 said:

Could this be a sticking valve / lifter issue??? Seems to be a common 996 problem - based on lots of Web info. Maybe its something you can fix yourself.

Hopefully a valve isn't bent.

Most likely diagnosis so far I think

 

2 hours ago, tomo said:

The lifters are fairly reliable according  to those that know , Failed chain tensioners,  or bore scoring is usually  the culprit according to those in know. 

Have scoped the bores and they all look good, will probably drop the sump and check underneath to be 100% sure.

1 hour ago, st3ve said:

Yes, perhaps tensioner blade failure (aka variocam pads, see the entertaining rebuild series on YT by 'Man in a garage') which allowed unstable cam timing initially and more recently jumped a tooth or three and bent one or more valves.  If that's all it is, and the contact was not too severe, then a minimum but quite acceptable solution could be just removing the one head and repairing the affected valve/s.  New chains and guide rails both sides (other head can stay on) and you'll be motoring again.

Of course nicer to split the case and replace pistons, rods bolts, rods, install new crank bearings and IMS chain/paddle etc etc, but that's in the mission creep department.  It's the variocam pads that seem to go way sooner than other stuff in the 3.4's.  A 15-20yr or 1xx,000km service item even?

Man in a garage is excellent! Depending on quotes I get for head work (lol) I'd be satisfied doing that. Car isn't worth investing $xx,xxx to get it mint, if it needed that much engine work I'd cut my losses and sell it as is. Just gonna have to ring around a few places in Melbourne and see what further damage that will be.

 

26 minutes ago, tomo said:

Yes, Do a bore check with one of the cheap camera jobys you can get for sixty  $ then you can eliminate the big $ fix.

Done and done - check out #6 - obvious stuck open valve marks on piston head. Cylinder walls all good though and no munched metal debris that I could see.

 

I've got a Z on the way next year 🤪 , so can bench the 996 for however long I can put up with it taking up room in my garage

 

20210812_15_52_00.png

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2 hours ago, slknv said:

, will probably drop the sump and check underneath to be 100% sure.

I've got a Z on the way next year 🤪 , so can bench the 996 for however long I can put up with it taking up room in my garage

 

Yeah - dropping the sump is probably the best first-start. Lots of plastic debris will give a good indication !!!

What type of Z is coming? I have a JDM G37S (which wifey will ride in with me), Its been a VG & fast 2+2 car

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On 21/08/2021 at 18:12, Zelrik911 said:

What type of Z is coming? I have a JDM G37S (which wifey will ride in with me), Its been a VG & fast 2+2 car

New Z - I've put a deposit for a yellow one, but thinking I might change to blue... hard decision, both look amazing! Wife is already upset, saying I've already got too many cars I never drive... but you know the saying, happy husband, happy.... something? This is gonna be the last of the breed, twin turbo true manual JDM sportscar, absolutely cannot wait for it!

Might use Victoria's never ending lockdown as a good time to strip the head off and get the 996 back on the road - will start this weekend!

 

Nissan Z.jpg.ximg.l_12_h.smart.jpg

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