Saturday - cold started & drove normal
Sunday - 1st attempt cold started and clunked. Turned it off and it ran normally.
Monday - This morning I attempted to start and it ran very rough bucking so I turned it off and tried again. Now it will turn over but not run so I left it in the garage. Tonight I try again and it did the same start and clunking. No leaks just knocking.

I researched rough idle, starts, and knocking but nothing really pinpoints my anxiety. Before I take it to the shop any ideas? Battery is good. Maybe is it's the gas? CPS? Vacuum leaks?

 

DON"T CRANK IT AGAIN.

There is a chance you have coolant in a cylinder or two from a blown head gasket or a more ominous crack.

If enough moisture is in there, and your crank it, your engine might be hydrolocked and you could bend a rod or damage other components. Water and coolant will not compress. They possess the wonders of hydraulic power... which is bad news for your engine... such that it could prompt a redbuild.

When you drive, your are expelling enough moisture... but at shut off just enough builds up that upon starting the water is enough to almost hydrolock the engine (CLUNK).

If enough gets into a cylinder, nothing will compress it. If your starter is strong enough, you will cause critical damage.

CLUNK.... PLUS rough running = STOP doing that

.

 

Clunking sounds from your engine are never good. Have the car trailered to your mechanic for a proper diagnosis. Further starting attempts would be ill advised.

 

cheap and quick: disconnect the MAF and try again. if smooth running with it disconnected, there's your issue. happened to me last year. i barely made it home, having to restart at every stoplight after conking out. CEL ablazing.

but so as not to totally disagree with the other poster, use your judgement - if it sounded localized (i.e. maybe one cylinder? maybe IMS? maybe a camshaft or something?) DONT START IT AGAIN. but if it sounded like a general problem, like an all over kinda thing ("bad gas", "vacuum issue", etc), then try the MAF diagnosis. when i had my issue, i was pretty sure it was the entire engine having a fit and decided to chance the short drive home.

 

If there's enough coolant getting into the engine to hydrolock it, is there enough where some would have been expelled out the exhaust during the previous restart attempts? If so, OP, any drips back there or under the car?

 

Water can also be ingested by running thru standing water. Usually at a good clip and with water being sloshed up like a boat wake.

Anyway... cant diagnose.. but clunk at start and rough running means flatbed time unless you can determine issue without cranking it again. Can always pull the plugs and crank.

 

Could be any number of things. Bad gas (really bad gas), probably with some water in it.

Failing fuel pump.

The list goes on.

I'm with those that say to not start the engine again.

My advice would be to arrange to have the car flat bedded to a Porsche shop (dealer or indy, wherever you are most comfortable with and believe will give you the best service) and let a pro Porsche tech figure out what's going on.

If the problem is an internal engine problem not starting and running the engine may be the difference between an engine that is salvageable for a reasonable amount of money vs. one that is rendered into scrap that wouldn't even satisfy a replacement engine core exchange.

 

Thanks all. Car was flatbed towed this morning but no word yet.

 

Picked up car from dealer today and it ran like a champ. They said two issues..

• low oil
• clutch switch adjustment

They adjusted the clutch release and topped off the oil (inspected oil for shaving but none present). Doesn't sound right to me. I'm going to talk to my Porsche guru.

 

Not to me either. How low was the oil?

 

they love changing that clutch switch. you'd think it'd be more expensive. i.e. you'd think the stealerships would be making a ton more $ / have a super huge margin on this repair considering how frequently we've heard about this incorrect "diagnosis". mine was changed a couple wks ago when i brought it to them for starting issues (and no it's not the cable, the cable tested fine). i only let them change it because, in addition to them running many other elec diagnostics as well as fixing another issue i had as a courtesy, it was relatively cheap and it's an 8yr old tracked car so it can't hurt to do it as a preventative.

my bet is still on the MAF.

 

low oil clanking my be related to valve lifters, but that is not exactly 'clank' sound, empty lifters sound like somebody hits a skillet with a metal soon, high pitch metal 'clank', very audible at low rpm.

good solid heavy 'clunk' from the motor is usually not very good news.

 

I had a similar problem once. Very rough running on startup and clunking sound. Sounded horrific. The engine was misfiring on multiple cylinders. This happened a couple of times but was not consistent. They replaced all the ignition coils and the problem went away for good.

If you have the same issue, it will happen again eventually. Consider if this is a misfire situation and replace the coils.

 

Porsche doesn't have a replacement schedule for coils but they should be replaced with the plugs IMHO. My car was driven in then SW (dry and warm) and well taken care of but the coils didn't look very good at 40K. Plugs looked like new after 40K but not the coils, they started developing cracks.

 

What the low oil warning light on?

About all I can offer is if the low oil level and clutch switch were not the cause of the behavior the behavior will return.

That the engine has not gone boom by now suggests that the problem is not a severe internal engine problem, if that is any comfort.