DavieGravy

I went to start my car this morning and noticed a vary loud slapping noice from the engine. It was also idling very rough. Classic oil starvation symptoms.

I immediately shut the car off and checked the oil. It's full, although the oil is a little brown. It was changed 5000 miles ago by a reputable German car shop.

I started the car back up and left it idling. I continued to hear the noise for about a minute and then it went away completely. After driving the car around the engine sounds totally normal again.

The last time the car was started was just briefly to back it out of the garage to clean the carpet. I'm not sure if the short engine run and then letting it sit for 4 or 5 days had something to do with it.

The temps here haven't been cold at all. Very mild. 60s to 70s.

Is this a sign of the dreaded cylinder scoring? Will the problem likely get worse? Should I trade it in before the problem becomes catastrophic?

PCA1983

You forgot to mention how many miles on that engine. You should be aware that higher mileage engines can benefit from higher viscosity oil. Depending on the mileage and climatic conditions, you may need one other than what Porsche recommended when new. Check the allowable viscosities in your owner's manual. My 09 GTS with 74k miles still sounds good on cold starts in Florida, so I'm not changing yet.

DavieGravy

It has 104k miles. What viscosity would you recommend? I will change the oil myself immediately. I have no idea what the shop put in there. I assume 0w 30

J'sWorld

If you know what slap sounds like or something was definatly not right, of course you need to check it out for lots of reasons

A compression test is cheap and easy and a scope may be second in order if low compression is found. If its still running well your time may be limited.

This has nothing to do with oil viscosity. Oil is there to lubricate not fix mechanical ptoblems.

DWPC

Search for "scoring" posts. I'm not clear on whether a leak-down or compression test would verify the cause. This is why used car lots are a major market for Motor Honey and STP.

endless_corners

What about fuel pump(s)? When mine was starting to go out and getting starved for fuel it make some weird noises from the hood.

DavieGravy

I'm just going to change the damn oil myself. I have no idea what type of oil was put in on the last change and if they even bothered to replace the filter.

J'sWorld

No, but it will verify either rings(scoring) or valves(seats), or confirm that is NOT a problem.

How about instead of guessing, follow a logical workflow and eliminate possibilities. The compression test is cheap and easy and never a "Bad" idea.

DavieGravy

I changed the oil myself using a wix oil filter and mobile 1 0w 40 synthetic. The engine is now smooth as a baby's rear end. The shop that changed the oil last time overfilled it which I think could have been the cause of my issues. My oil level was always over the max which can cause frothing and result in a loss of lubrication. Now, it's half way in between on the dipstick.

J'sWorld

So oil starvation from frothing from being overfilled caused a very loud slapping sound and very rough running on a cold engine? Oil frothing immediatly after startup on a cold engine? In your op you said when you checked the oil it was full, not overfilled. I can tell you without a doubt that due to the crankcase design on the 4.5 your not going to get any frothing due to windage from being overfull. The crankshaft and rods are separated completely from the oil pan by the bottom of the bottom half of the crankcase. Solid alum. You came and asked for help because loud sounds scared you. I gave you a cheap easy check to rule out cylinder scoring and lost compression. Loud sounds happen for a reason. Cayenne engines arent cheap. Good luck.

DavieGravy

A mechanic would just say nothing's wrong with it after charging a bunch of money for this "cheap" compression test; assuming they would even perform such a test without wanting to do their own diagnostic work and finding other things to charge me money for. And let's say that there is scoring or lost compression; not cost effective to fix anyway so what's the point? I appreciate the advice but I've decided against it for now. If it happens again I will look into getting the engine checked.

deilenberger

Aside from possible physical damage - checked for as Mr. Haney suggests, you may want to have the ECU scanned for misfires. If the coils are marginal (and they ALL appear to be on the V8 engine), and one misfires and allows a plug to foul on cold startup.. which would be more likely if the engine was run briefly (as you describe with backing the car out of the garage to clean the carpet - leaving a VERY rich mixture in the intake..) it will idle rough and sound like crap.

BTDT MANY MANY times on fuel-injected cars. Volvos can do it so badly that they won't start. BMWs can do it with ease, and I see no reason Porsche is immune.

I make it a rule - if I start the engine - it at least idles for 5 minutes or so to allow the rich mixture to be sucked out of the intake. That prevents the next cold start from fouling plugs.

If you read the codes the ECU stores, it should show something like "Misfire with injection shutdown on Cylinder ##" and give a time it happened. It may also show "Fault not present now" - that's your clue. Probably time to start thinking about new plugs and coils.

Oil had nothing to do with it - I'll have to agree entirely with Mr. Haney on that, but don't immediately assume ebola because you have a fever.. usually it's just a cold (hope the analogy is understood.)

J'sWorld

Ummmm, the "point" is to unload the car while its still running well.
Ummmm, if you can change your oil the you can do a compression test. Obviously your to lazy and negative to google "compression test" to see whats involved. Loud mechanical noise on startup is never good. Im not screaming ebola, but if you have been around people that are likely to have it, you may want to get tested.

deilenberger

Sure you are. You've seized on total engine failure without the facts to back it up. Could it be? Sure.. but before panicking it would make sense to check the easier/cheaper/simpler things first.. and that involves hooking the P!G up to a code reader and looking for stored misfire faults. If you've been around P!Gs for long - you'd realize that is WAY WAY more likely a scenario (especially given the clue of starting and shutting the car off to move it out of the garage) then a scored cylinder.

Sometimes it IS the simple stuff. I like to start there and save panic for when it's needed.

BTW - calling someone "lazy" could be construed as a personal attack on most forums - and usually isn't much liked, by other forum members and the forum management. It also turns everyone off to whatever else you might have to offer, which might actually be good information.

J'sWorld

I guess time will tell.