McCulla

My CEL investigation is expanding and the next step is likely to be changing lifters. If this means pulling the motor (even a bit) I'll have the LN IMS retrofit done. Thanks!

997_rich

You/They think that you have bad hydraulic lifters? Can you hear any "ticking"? Which code makes you think they're bad?

Yes. you'll have to drop the engine... there's barely enough room in there to do the spark plugs.

McCulla

Yeah, I know...no noise. As I research this, the 0300 code for random misfire can be associated with bad lifters, which don't have to be noisy. At nearly 60 years of age, all my "bad lifter" experiences have been accompanied by noise. Go figure. Since I posted this thread this morning, I have been to visit my tech and he says the lifters can be changed by dropping the mufflers, valve covers, cams and go from there. Hope he's right....

997_rich

Maybe if you pull the mufflers fender liners etc... I'm not sure if there's enough clearance to get the valve covers off- maybe I'm wrong. But then you've got to pull all the other top-end junk before you get to the lifters.

Before I got into this, i'd make sure I investigated all the the other sources- coils, ,ground wire, CPS, etc.

MLindgren

Your car is an early '05 and doesn't require engine removal to install the LNE retrofit kit. Is your car being serviced at a dealer or independent. Is the repair all covered by your additional warranty?

McCulla

Car is at an independent. This stuff is "supposedly" covered under the warranty, nothing has been an issue to date getting coverage. It's pretty expensive stuff and they send a rep to check on site (which hopefully will happen Monday (holiday weekend). Unfortunately, the list of things he's been over (this is the 3rd time for the CEL) is long. Ground, coil packs, injectors, contaminated fuel, plugs, compression, ECU. When I got there today, the car was running, and hooked up to the computer. He pulled up a number of comparison parameters in real time (that I honestly don't understand) to show me my car vs normal. After trying to eliminate the above mentioned stuff, the next things on the list are Vario-cam solenoids/actuators and lifters.

I'm aware that the engine doesn't need to be pulled to do the IMS on this year car, but even if the drivetrain had to be disconnected a bit (like at the trans/clutch area) to get to the lifters, that would justify taking the step to the IMS retrofit. It doesn't sound like that will be necessary for this, but the process is still fluid...if anyone is interested, I'll keep updating over the next few days.

Thanks to everyone for your replies. Great forum.

Byprodriver

I don't believe a lifter can cause a misfire CEL. Vario-cam function can be verified with the proper diagnostic equipment. You should take your car to a Porsche dealer.

MLindgren

Keep us posted. I'm surprised the warranty company hasn't insisted on getting a better diagnosis at a Porsche dealer.

McCulla

There was a thread on this subject within the year that alluded to the fact that a lifter can cause a misfire. Even if I only thought about it logically (and that could be completely wrong..) I can envision a delay in valve opening/closing that would throw some part of the cam consitency monitoring a curve. There has been a long post recently about he "definition " of a misfire. There is absolutely nothing sensory about this problem. I feel nothing in the engine running, at any rpm, load, or idle. There is no stumble or hesitation. The car runs exactly as it always has, but I have a repeated CEL (same code group, including specific cylinders). As I understand it the term misfire as it applies here is not how I would have applied it many years ago, where I would have expected to "feel" something in the way the engine runs. One of the items that is included in the long list of things that can cause "ramdom misfire" codes are the cam position sensors. Mine check out fine. It sounds like the next layer of investigation in that part of the drive train is the actuators and other Vario Cam components. If anyone can confirm the fact that lifters cannot cause a misfire as it is defined in this context, I'd love to hear it---no sense in spending the time, or money if it's a dry hole.

McCulla

MLindgren, your comment about the company insisting on a dealer for a diagnosis may yet happen. Their rep has not visited the shop yet, and I'm sure he could mandate that. I'm happy to oblige. (Wow, this rented Yarus is tough...)

McCulla

Here is the post I was referring to about the lifters/misfire:



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Quote:
Originally Posted by s2Rick
OK.,Maybe 6000 miles on an engine that went through an ims bearing failure. New chains,L&N updated shaft and bearing new gaskets etc. Everything drove fine for about 5000 miles. In the process of putting on a fixed wing the car sat in my garage for 3or 4 wks.During that time we received 8 inches of rain in a weeks time,but the car stayed dry.Started mis firing when started driving after this wing addition Also purchased the wiring harness to by-pass the power from the original spoiler. Thought maybe moisture and ran additives to dry any possible water in fuel.Then put in new plugs,then new coils,then a new maf sensor no change in mis fire and new air filter. It shows up on the scanner in different cylinders and # 1 cy. seems to also misfire on a regular basis as mis fires on low rpm's especially when first starting off in 1st gear but can run in 4th gear and slow speed to 30 or 31mph and it will mis fire. at higher speeds it seems to run great. It does'nt do this every single time but the cel will flash when the problem is worse than other times.I did not put on the cold air take till after this problem started. Do not use any kind of lube for any air filter. My indie thinks it may be fuel related as stated before. He wants me to leave it with him for a few days to check out. Also sprayed some on the engine while running to check for vacuum leaks. any ideas? Thanks

If misfires started after wing installation while I'm not familiar with the job one has to suspect something disturbed during this operation. An non-spoiler related section of the wiring harness possibly damaged, one that perhaps connects to a camshaft positon sensor or VarioCam Plus camshaft solenoid.

Or a fuel pressure regulator vacuum line/connector/wiring harness got damaged. A fuel pressure check out seems called for. (More on this below.)

That you have replaced the plugs, coils, MAF you have eliminated the more common sources of misfires which suggests the failure resides elsewhere.

The sitting around weeks unused then the symptom appearing does by itself have some significance. It does add considerable weight to your tech's opinion the symptom may be fuel related.

If the fuel filter is a servicable item it may be worth doing this. But before I did this I'd consider draining the gas tank and refilling it with fresh fuel. It may be worth while, worth cost to open the fuel system as close to the injectors as possible and at the same time a fuel system pressure and delivery test performed.

Another check out worth considering would be removing the oil filter housing and carefully dumping its content of oil and filter into a clean drain pan and looking for any evidence of debris of a sinster nature.

That the engine experienced a IMS bearing failure and was resurrected could mean -- it depends somewhat upon the rep of the shop who did the engine -- that some IMS bearing trash ended up in one or both VarioCam Plus actuators.

With the proper diagnostics computer the tech can control both the camshaft advance/retard feature and the variable lift feature and observe the various sensor activity (O2 mainly) to know that this system is working properly.

Briefly, while this is from a Turbo reference I think it may of some value: a Cycle of 1000 crank revs is evaluated. For misfiring that puts the TWC (3-way converters) at risk, 200 revs.

If the misfire rate is greater than the threshold value a fault is recorded.

The CEL is turned on and stays on when the misfire rate stays above the threhsold value at which emissions limits are exceeded during 2 consecutive driving cycles..

If the misfire rate may lead to TWC damage the CEL flashes. If the misfire rate is not reached during the first trip the MIL goes out. If the rate is reached during the 2nd trip the CEL flashes. If this misfire rate is subsequently no longer reached the CEL changes to a steady on state.

Misfiires are not recorded if the fuel tank is nearly empty.

In the event of a short circuit to B+ or ground in the O2 sensors ahead of the TWC, teh mixture becomes too lean or too rich. This can cause misfiring. If an O2 sensor fault is stored in DTC memory the cause of the O2 sensor fault needs to addressed first the faults cleared and the vehicle road tested.

Ok misfire possible causes...

Ingition system fault.

Injection system fault.

Flat-base tappets (valve lift fault).

Mixture too rich.

Mixture too lean.

Valve lifter chattering. This is caused by dirt in the lifter. One might hear this chattering during the misfiring. (To hear this over the noise a misfiring engine makes almost certainly requires listening to the engine camshaft covers with a mechanic's stethescope to detect valve noises.) The mixture adaptation values [long term fuel trims I think] are normal.

Now this chattering, if (big if) caused by dirt, this dirt might come from debris from the IMS bearing having gotten into the valve lifters. (My info is that when a Porsche tech evaluates an engine that has experienced an IMS bearing failure he checks for IMS metal/debris on the 'clean' and high pressure side of the oiling system, for instance checking scavage pumps in the heads. If any metal debris found in these then the metal debris has gotten into the lifters, lifter bores, etc. and the engine is not a candidate for rebuilding.)

However, the manual does go on to say remove the lifter bores [lifters I think] and check for damage and blow out the oil passages. Replace all lifters. During test drive listen for lifter noises.

Another possibility is the camshaft control times. No chattering noises occur. The DME signals misfiring for bank 1 or 2. The mixture adaptation values in the idle speed range differ from bank 1 to bank 2.

(I observed this in my Boxster while its VarioCam solenoid/actuator were acting up.)

The mixture ranges in the upwer and lower load ranges were generally normal.

(I observed this in my Boxster while its VarioCam solenoid/actuator were acting up.)

There is more, serveral pages worth (at least) that cover testing the VarioCam timing/lift action and fuel pressure/flow and so on. Best for you and me if you want the info PM me with your email address and I'll make a PDF copy and send it to you.

Sincerely,

Macster.