cec3

997.1 GT3 engine developed a nasty noise at the track the other weekend. Noticed after the end of the session as I was driving back to garage - plugged in cheapy OBD-II reader which read cat faults (aftermarket cats), and misfires of cylinders 1, 4, 6. Oil level, pressure, coolant temp, etc all fine and car ran good on track (no money shifts - I typically short shift it around 8k). Oil filter clean, no metal debris, oil color/translucency good. Put it on the trailer and came home early



engine miles=12k (mostly track)
Fabspeed headers/cats/exhaust, BMC intake, chip (all done very early by previous owner)
number of ignitions, range 1 = 33 (from previous owner - no over-revs in the higher ranges)

shop where I left car is backed up so I thought I'd hit up RL for suggestions

Jamie_GT3

Does the noise change clutch in or out? It seemed to change with rpm...

Maybe clutch related...

cec3

no change with clutch action, only with rpm's

Mvez

You need a new set up spark plugs. It will clear all your misfires and fix your problems.

AudiOn19s

Ched, that's terrible luck. Could actually be something dumb. Check little things that are known to go wrong with these cars.

Plugs are known to come loose. Crank pullies come loose.

As others suggested these things tend to have pressure plate, throw out bearing problems but it would show itself in functionality when driving back into the pits so I doubt that's an issue but at the same time could cause misfire codes since the flywheel has the crank trigger on it.

I don't think any of the old 3.6L cars had issue with cam bolts backing out.

Struggling to think what else it could be...at least anythign else that doesn't end with a trip to Sharkwerks for a 3.9 conversion

Spiffyjiff

check MAF also.

tcsracing1

hopefully it is not your crank case..... it has been known to create sounds before failure...

I couldnt really tell from the video....

M3EvoBR

hard to tell from the video, check any external moving parts as it's rpm related.
like pulleys, belts, anything that can have friction. Hard to tell from the video, if live, it would be easy to identify if it's a rod knock or engine related.

Mvez

I'm telling you, I just had a CEL giving misfire codes, and plugs fixed the problem.

My car sounded just like that. I first checked the coil packs on the misfiring cylinders (and they were fine), so next is plugs, which fixed everything.

I almost guarantee you it's a coil pack or spark plugs (or both).

Also, check your exhaust system for leaks, which causes the accelerated wear of coil packs and plugs.

Check the low lying fruit first.

cec3

Thanks guys - will check plugs n wires

Mvez - u b at PP w/ KyPCA?

Andy - when u at M-O next?

AudiOn19s

good question...I'm transitioning to a new job and I'm not sure about time off in the near future.

I'll be there Labor day for sure for a single day lapping event. Beyond that OVR and NOR's Mid Ohio events are strong possibilities as is KY's Putnam event but I won't be able to do Friday's with any of them for the rest of the year which stinks.

sharkster

Just wondering do you have a LWF as well? In any case I would have someone check your cam-adjusters. See if the screws are backing out (another crap design). At least drain the oil and see if you have aluminium shavings (that'll be from the housing as it gets carved away).

cec3

Alex,
no LWF, will add cam adjusters to the suspects list -thx!

996FLT6

Any loss of power while on track? With a failed coil pack it would be very noticeable power loss. I had cylinder 6 misfire due to bad maf and visually spark plug #6 had a lot of carbon bu. For example normally at brake zone of t1 at thill I'm at 135-138 mph range I was stuck at 114-118 mph. Mike

sharkster

OK with a dual mass it's less likely the cam adjusters but I'd still check when on the lift. The noise is quite distinctive though. The video.. it's hard to tell really