Oh crap. What should I do?
 

Today I was at Road America for a track day. MVP Track Time does a great job, and puts on a great event. It's well run and the instructors (at least the one I was with) are very good.

However, on my third session, coming out of turn 13, I noticed a vibration. I immediately backed out of the throttle partially just to get around the last corner to the pits. I didn't hear any weird noises. When I got into pit lane, I up shifted so I was running at lower RPM, and the vibration went away. So I drove back to the paddock keeping the revs fairly low. I let the car cool. After a while I took the car for a drive outside the venue. Across the street was a country road, and I headed down it. I played with speeds and there was no vibration up to 50mph. Then I turned around and played with RPM. Above about 4000 rpm, the engine felt rough, and gets worse at higher RPM (only went to about 5k). Because it felt very consistent and even, it feels like a vibration. Again, as long as I kept the RPM low, the engine felt fine.

So I packed my stuff up, crossed my fingers and started my 2.5 hours home. Luckily, the drive is almost all highway, so I just kept the revs below about 3500 and drove it. I got home with no problems, and by that time I was thinking that maybe I had imagined the problem, or that it was something other than the engine. I needed gas, so I stopped close to home, and on the way home from the gas station, I drove it up into the 4000 rpm range in 1st gear (slow speed). Yup. Same problem.

When I was driving the track, I noticed a vibration in the car a couple of times before this. In a hard turn that I got into a bit hot, I would get a bit of under steer and felt a vibration that I'm pretty sure was from the front tires. When I had the problem, I initially thought it was the same thing, but it didn't go away when I got going straight again. I've been racking my brains over this, and I'm pretty sure it was a different feeling vibration, but I could be wrong.

No fluid leaks, no funny noises. It really just kind of feels like at higher RPM the engine starts running on 5 cylinders or something. It feels like it's running rough, but it's a completely regular, consistent roughness. It's not something where it runs lumpy or anything. It's not like the mixture is out of whack and the car is just running crappy.

So now I don't know what to do. I'm thinking about changing the oil and maybe getting an analysis (unless I obviously find metal particles, then I know it's an internal failure). I don't know if I should take it to my Porsche shop (Fischer Motors) or what. What do you guys think I should do to ID the problem?

Could be a spark plug or coil, it could also be that you lost a wheel weight. Does the vibration come with a loss of power?

I'm pretty sure that your check engine light would illuminate if you lost a coil pack or a spark plug. I had a CEL illuminate when one of my coils went bad.

I don't think it is a wheel weight. The vibration from a wheel weight would be dependent on the car speed, not the engine speed.

Its not internal. If it was you would have scattered the engine on the 2.5 hr trip home..

Probably a coil pack died or came unplugged and no the CEL won't illuminate in some of these instances. You also could have fouled a spark plug..

Wheel weights come into play when high wheel speeds are high, so if the issue happens in first gear above 4K RPM you can bet its not a wheel weight.

IMO, a wheel weight can play havoc at any speed depending on a myriad of factors including how heavy said weight is. The key is a lost wheel weight may be dependent on a particular speed to experience but will not be intermittent in nature in respect to repeatability.

Thanks for the input guys. It is definitely not speed related, but it is definitely rpm related. A coil pack makes sense. The engine does really feel like one cylinder isn't firing at all above 4k rpm. I think a plug wire would be intermittent. I'm going to pull the plugs today and see if any have a different look to them or smell of unburnt fuel. I may do a spark test on them too.

Thanks again for the input. I'm glad Jake thinks it's not internal. <whew>

C'mon, Mike...is it speed related or not?? :D

:p

Fixed.

So... what was the fix? :confused:

Read his 9:23 post (which used to say, in part: "It is definitely not speed related, but it is definitely speed related.") and my 9:45 post. That was the "fix". (Far as I know, the car still needs work.)

have you ruled out the engine mount?

Well, I kinda did automatically because it didn't seem related to torque. If it were an engine mount, I'd think that torque would cause the engine to rotate (equal and opposite to crank rotation) regardless of rpm. The rotation of the engine would cause some kind of vibration-type feeling.

Does anybody have any suggestion on how I can troubleshoot the problem and identify what's causing it?

do you have a durametric unit??

Nope. Wish I did though.

Here's what I did recently... I bought the Durametric, and showed Cyl misfire #5. So... I swapped coil pack between cyl 5 and 6 and guess what??? The next CEL code threw a Cyl misfire in number 6. Bingo!!!

So...

1. read your code on the Durametric
2. swap coil packs on adjacent cyl AND...
3. swap plugs on OTHER adjacent cyl
4. clear the Durametric code
5. drive car, run engine up to the 4k+ RPM
6. let engine cool, drink a beer (or two)
7. read the code again and see which cyl the problem follows
8. order parts
9. take girlfriend out to dinner

This procedure took me an hour or so. I'm assuming you have ignition issue, and guessing a fouled plug. My coil pack issue wasn't rpm related, it was intermittent. I hope this helps.

:cheers:

I owned my NB for about two years before I bought Vag-com. Durametric will be one of the first tools that I buy most likely before I buy my 986. Most certainly if it tells me that rev history on the engine.

"Does anybody have any suggestion on how I can troubleshoot the problem and identify what's causing it?"


Jack up your car, pull the spark plugs and inspect the plugs and coil paks. The misfire cyl spark plug tip will be discolored (usually black or wet) compared with the other 5. Inspect the coil pak on the offending cyl and look for cracks or signs of arcing. Replace failed parts. Easy breezy.

The Durametric is nice but any simple $60 OBDII reader will also give you misfire codes that identify which cyl. is the problem.

One simple thing I forgot to mention... stop by Autozone and get them to read your code with their Actron. Not as detailed as a Durametric, and dont think it can clear codes, BUT you might get an early indication while you're waiting on your $300 Durametric to arrive in the mailbox :)

I don't have a CEL so AFAIK, I won't have a code.

I do have an AutoTap, which is supposed to work on all poast-'98 cars. So that should give me diag info. I'll try it this weekend.

I hooked up the AutoTap today. Even though it doesn't show a whole heck of a lot on this car, it did show me two codes. I'm getting
P1313 - misfire, cylinder 1, emission relevant
P1316 - misfire, cylinder 4, emission relevant.

So at least I know the cylinders involved right now. I still have no CEL, and it seems to be running fine now. Looks like I'm going to have to swap the wires and plugs and see if I get any more problems. I'm a bit worried that I'm not going to find anything since the car is running fine again.

Do you guys think it could have been bad gas? I filled up just before I got to the track. So I probably drove about 30 miles after filling up before the problem. I filled up again when I got home and haven't driven it much, but probably about 30 miles give or take.

Well, it died today. I've had to drive it to work even though I haven't fixed the problem. It's been running fine though (I've been avoiding high revs). Today, on the way to work, it started running rough at lower revs. When I exited the tollway and pushed in the clutch, the car died. I restarted it and it just ran rough. Something was making a squeaking noise (it sounded like an exhaust shroud squeaking). I turned off the road, shut it off, and coasted to a safe place. Waiting for a tow truck now.

The plugs are 4,000 miles old, the MAF and O2 sensors are about 15k miles old. Not sure what I'll find out.

When you changed the plugs did you do coilpacks too? How many miles on your car? If you have 40k or more and are on the original coilpacks I would have them changed. I have had two other Porsche's (996 and Cayenne) with higher miles and in both cases the coilpacks were shot. I do not think they are that much money and should be considered a wear item every 40-60k in my opinion. When they start to go it can be very intermittent and it is just better to replace them every couple of years. IMHO

How old are the O2 sensors? Did you google those codes to see what other people did to resolve them?

I did not change the coilpacks when I changed the plugs at 60k. It's got 63k now. The O2 sensors are about 15k old, same as MAF.

A set of coilpacks are almost $300! That's not like changing the wipers.

Wouldn't a port reader direct you to a certain coilpack to inspect? Have you pulled the plugs again? An inspection of the plugs might give you a lead on which cylinder is firing unlike the others. Three bills does sting but look at it this way, if you have to play a bit of "replace and pray" at least it isn't at $100.00 an hour with someone who doesn't love your car wrenching on it.

The logical next step?? Or... take it to your favorite local mechanic. My money is on cracked coil paks. :)

You were all wrong. It's a bad main bearing. :barf:

Not sure what I'm going to do, but I suspect I will be selling the chassis and eating what I owe on the car rather than putting thousands into the car and having no guarantee that it will be any better than the car is right now.

I feel for your predicament having a major breakage like that. I think Porsches fitted with the M96 engine that are tracked really need the deep sump kit that helps prevent oil starvation under high cornering loads.....
As a matter of interest, how was the main bearing damage diagnosed?
You say that the car has been "running fine" after the initial vibration & rough running - I would have thought that you would have heard a bad main bearing, even at low revs.

I didn't ask how he determined it was the bearing, but he did say it was scored. He said he didn't look at the crank. Not sure how he got a look at the bearing, especially since they didn't start looking at the car until late in the afternoon. I'm going to ask him tomorrow.

When it did finally stop running, I did hear a bearing noise.

Everybody told me that I only needed a deep sump if I had slicks. They said you wouldn't generate the Gs with street tires that could cause scavenging. I guess they were wrong.

Actually the engines that fail on the track only appear to fail from starvation...

Most fail because their oil temperatures soar and the oil doesn't have the capability to protect the components or maintain pressure at these temperatures that are generally 250-265 degrees.

Here are some examples from one of our test cars running a bone stock 3.2, just purchased in May of this year from Porsche. The oil was Mobil 1 10/40 for these tests, we used these for baselines for ongoing lubricant development.

When an engine dies due to a lack of oil pressure from overheated oil, the symptoms will fool many into believing the issue is starvation. This data suggests oil that is being cooked well beyond the point where pressures drop off significantly.

That said, I may have a buyer for the car with the blown engine.. I have a wait list of those who are looking for a car to equip with an upgraded engine who don't care if the engine is currently scattered.. It won't bring much, but at least you can move it.

Thanks for the info Jake. I may be giving you a call tomorrow.

BTW, I don't know that the oil was an issue. I didn't have any warning lights when the problem first occurred.

You won't. Thats because their is no warning light for overheated oil and the oil pressure has to be at a point where the pressure is so low that the engine is already dead before it illuminates.

They call them "idiot lights" for a reason :-)

Ah. "Illuminating" (pun intended).

So, if the oil overheated, and there was insufficient oil pressure, that means not only is the bearing shot, but the whole engine probably suffered severe wear. Right?

I also wonder what could be done to prevent that. Would a center radiator cool the engine enough? Would the 160 degree thermostat be enough? Or is there an aftermarket oil cooler? Seems like that would be the best solution, though I image that would increase oil pump requirements, and capacity requirements pretty significantly.

What happend to you (and Jakes printout confirms) is why Porsche do not use the M96/97 engine in their serious performance or race cars. Especially without some major internal upgrades
The engines in the 911 Turbo / GT2 / GT3 are completely different to the M96/97 series Boxster / Carrera cars, being genuine dry sumped 70 series engines, originally from the GT1 racecar.

Note that the coolant temps were just over 210F, normal.. A lower temp T stat would have helped a tad, but not much as the oil temps are at such a great differential to the coolant temps.. Oil temp is just that, oil temp.

The key is:
1- Run an oil developed to operate at temperatures in excess of 250F for sustained periods of time without a loss of pressure or lubricating properties

2-Run an external oil cooler.

NOTHING else is going to be the answer.

The reason why these engines run high oil temps is their tight clearances coupled to tons of friction from 24 valve springs, 5 timing chains, 7 main bearings and etc... The engine is a friction nightmare, so its hard on oil.

Adding a larger oil pump won't make the issue any better, thats just going to make the oil HOTTER!! Bigger pump= even more friction.

Some oils can run 250F+ sustained without issue, but these oils need to be changed every 5-700 miles and cost 13-15 bucks per quart. They do not work well at lower temperatures. Thats the difference in a "race oil" and "street oil".

Either keep the temps down and pressure up or use an oil that will maintain pressure at temperature.

Either way, the issues we see with failed engines on the track aren't from G force aggravated starvation.

But isn't there some additional
 

steps you can take to prevent oil starvation at high-G forces on the track with track tires?

Things like running a baffled sump? Deeper Sump? Additional oil pick-ups? A device that mounts in the trunk and accumulates oil at pressure and then feeds it to the engine when it senses starvation (accusump)?

If you always keep oil between the metal parts, won't the engine temp be lower and the "water" have to work less hard to get rid of the heat?

I'm all for the third radiator and the bigger oil/water heat exchanger too, BTW. Just wondering if there aren't many preventative measures needed.

I have been following this thread and I am very curious now how a "scored bearing" results in:

"P1313 - misfire, cylinder 1, emission relevant
P1316 - misfire, cylinder 4, emission relevant."

These issues may both be true but certainly seem unrelated. Anyone have a clue how these very different conditions might tie together? :confused:

I've been wondering the same thing. Haven't talked to the shop again yet. I'll ask when I do.