Higher RPM misfire diagnosis/cure tips?

[pcroyle]

My 2002 Carrera 2 develops a consistent CEL with 0300/0301/0304 misfire/misfire codes at just under 6,000 rpm. Makes track days very irritating. I've replaced all of the plugs and coil packs, car idles smoothly and otherwise accelerates up to just under 6000 without drama/variocam kicking in at 3000. But the misfire codes with CEL persists. I've cleaned the MAF sensor and car idles smoothly, operating normally up to 6000. I do feel that the engine just isn't as "bright" as it should be nor as smooth through the middle rpm range on its way to the CEL at 6000 and beyond.

I suspect a collapsed lifter or a fuel injector problem. My local independent shop wants to do a compression test, check the engine management computer for the most recent software and " . . . go from there." My issue is, I'm afraid to follow him down the rabbit hole fearing that there is no "there","there" a few thousand dollars later.

What should be my order of constructive events in getting to the bottom of this aggravating issue?

And many thanks!

[RFM]

Sorry for the late response, i spend a week in southern France. I would take a closer look in the cat. area, such symptoms at higher engine revs are not uncommon with a cat. on his end.

[DBJoe996]

P0300 Random/Multiple Cylinder Misfire Detected

P0301 Cylinder 1 Misfire Detected

P0304 Cylinder 4 Misfire Detected

Since the cylinders where the misfires are detected are on opposite sides, I suspect it is not one of the catalytic converters going bad (could be both but not probable). I would start again where you left off...plugs, coils, connectors on the affected cylinders, change them out (again) or swap them and see if the errors change to a different cylinder. That might help you isolate the problem to a specific coil pack. Plugs gapped correctly? All the same and correct type? Even the smallest problem with the plug or coil pack (carbon trace) could affect the high RPM spark and throw a error code. When was the last time you ran some Techron through it? Sorry....mainly guessing at this point. A Durametric or the dealer might be worth a visit...

[pcroyle]

The coil packs and plugs are all new, matched and installed by a pro. Had the same exact codes prior and after that. I have and use a Durametric. I seem to have a "lazy" O2 sensor on the passenger side bank 2 and will replace it with a Bosch 16433 part number direct fitment new one later this week. I haven't checked closely but if the O2 sensor installed are not Bosch or are not matched, I'll replace both pre-cat and get that done while I'm at it. I'll have the car back on the ground this weekend and will go out and take some live Durametric readings and run it up to redline under load--if I can get that far--with out a CEL!! I have NOT used Techron yet but that's also on my short list--10 year old car, 34000 miles--and a bit cheaper than sending the injectors off to have them balanced and blueprinted, although that's what I'd also like to do . . . ..

Edited October 8, 2012 by pcroyle

[DBJoe996]

There was another thread about a similar issue here, at least throwing some of the same codes:

http://www.renntech....-start-misfire/

Sounds like your plan is a good one and you are on track. I was wondering...how well did you clean the MAF and have you changed/checked your air filter? Are you running stock or aftermarket air cleaner? The MAF really comes into play at 4000 RPM and above, although it would affect all cylinders. Maybe the live run with your Durametric will give you some further clues. I would go ahead and run the Techron as well, looks like with the low mileage the car doesn't get much daily use and therefore the injectors might be a bit gummed up with old fuel.

Edited October 9, 2012 by DBJoe996

[pcroyle]

The airbox is aftermarket but uses the paper stock filter element. I cleaned the MAF really well with mass airflow sensor cleaner as directed and have cleaned up the throttle body. I've received mixed messages about running Techron through it and have no oil changes planned to rid the crankcase of any that may leak past the rings; so, I may hold off on that a bit longer. I'm just trying to get the things related to the sparkplugs firing "symmetrical" with the same parts, same age, etc. After I've hung my FD Motorsports-modified mufflers this weekend, I'll do some live readings with the Durametric and report if I've been successful in any regard! Thanks for your advise.

[pcroyle]

I just replaced what obviously are the original pre-cat sensors. Bank 2-the one the Durametric identified as "lazy"--was black with carbon; Bank 1's was nice and dull uniform grey. Leads were frayed through the insulation on each but wires otherwise looked good. Now good to go. I hope that balances out the harmonics between the banks and eliminates my general and cylinder 1 and 4 misfire codes so that I can really enjoy this thing up high in the rev range where it belongs . . .. If not, a can or two of Techron is next step.

[pcroyle]

Just replaced my O2 sensors while my mufflers were out at FD Motorsports being "hacked." Put the car back together this afternoon. Mission largely accomplished! My misfire/CEL now comes on at just under 7000 rather than just under 6000 and of course the car sounds sweet with the FD muffler mod. So, on to the next step--a can or two of Techron. But it looks like the car is now ready to hit a racetrack here in Florida without further issues if I can exercise some discipline with the rpms.

[pcroyle]

After a single bottle of Techron, I still have the same codes as reported above that trip a solid CEL at 6600 RPM consistently. I doubt another bottle of Techron will make any difference so I will not use another at this point. With the plugs, coils and O2 pre-cat sensors all changed out, I've improved my situation from a CEL at 5800 RPM to now a solid dash light at 6600 RPM. I'm only 500 RPM short of fuel cutoff; so, my question for all of you simply is this: If I ignore these consistent 0300/0301/0304 Durametric codes, DON'T rush home to clear them and otherwise go about my business, do these codes set off any response in the DME that reduces performance in any way while the CEL is lit or that cause a condition that will eventually harm the engine/peripherals if left uncleared or solved? Your input most welcome and thanks!

[pcroyle]

I'm installing a new MAF tomorrow. Stand by . . . . .

[pcroyle]

No joy . . . . Same flashing CEL at 6800 rpm on a single run up to that level last night that doused itself in the next quarter mile or so of more "normal"driving. Guess I'll live with it--for now. Tracking the car at Sebring 1.19.13.

[pcroyle]

Well, had a blast at Sebring 1.19.13---while it lasted. Around 3:30 p.m., my #6 piston let go at the wrist pin. Flat tow, AAA assisted, back to Boca Raton and am almost done with the installation of a donor engine from a totaled 2002 (bent tub; otherwise damage unremarkable). Engine is bone dry/never been opened up/factory work still obvious. Swap and all related work being sourced and performed by Mike Alves and Elli Weiss, Boca Tech Auto Center, Boca Raton, FL. Best little independent shop in town for all of you readers within reach of Boca Raton.

Since we had the opportunity, an LN Engineering IMS bearing installed, 160 degree thermostat, LN rear main seal, new plugs, fresh radiator expansion tank and injectors balanced and blueprinted by Marren Injectors in Connecticutt. Porsche fluids for tranny and radiator; Joe Gibbs DT40 engine oil that will go out for analysis at LN at 6 months/5,000 miles. LN magnetic drain plug as well. We have a GT3 Cup shifter cable installed and are waiting on either used or new rod ends for the interior end of the cables in order to get the car drivable again. Can't wait to try out the Numeric Racing short shifter, also installed.

And that, as they say, is that . . . .

Edited February 22, 2013 by pcroyle

[EleCTriCT]

pcroyle

"We have a GT3 Cup shifter cable installed and are waiting on either used or new rod ends for the interior end of the cables in order to get the car drivable again."

What are the advantages of the cup shifter - as I dont get to see many "Cup Car" Parts. is it like a factory short shift kit?

[pcroyle]

The advantage to the Cup cable is the additional stiffness of each cable--about 1/3rd larger in diameter than stock. It's only available through dealers/shops/race shops aligned with Porsche Motorsports. My car has a shift feel now that seems as though the transmission is right below and connected to the lever in the cockpit. But I"m also using the Numeric Racing short shifter inside the car. It's plug and play and amazing. Check it out.

Disadvantages to the Cup cables--because the ends are metal and not buffered through plastic, at each end, it's transmitting alot of noise into the cockpit--enough that I'm likely to change out the Cup cable for a modified cable that Numeric sells that has some buffering materials at each end. The noise is noticible, I don't think I can get used to it (and I'm pretty hard-core) and I haven't even suggested that my wife and I take it for a drive since I got the whole car home, it's that noticible!

I'll give it 30 days more . . . .