gio_73

all the coils are brand new, and i have also tried swapping the new coild around. Misfires are random on all cylinders.

I have not tried replacing the MAF sensor, nor cleaning, however would I still be getting a good range in the readings and no code when scanning if the MAF sensor was malfunctioning?

utkinpol

range by itself is not an indicator - maf reading should accurately correspond to current engine load.

but, you know, it is difficult to speculate of what happens there. i just say - to wash MAF sensor is a simple DIY job and who knows, it may help. realistically you need to have car on a dyno with PIWIS connected to it and run tests under load to see what is going on - a bad DME, bad valves, coils, plugs, who knows.

a guy i knew here in MA had similar issues with random misfires and his problem was an acting valve lifter (1) as it was causing those issues. if car is off warranty it is an expensive problem to assess, unfortunately. good luck, i hope it may be something simpler than valves.

ask dealer to try to swap DME if they have one around to see if it fixes it. who knows.

Macster

The manifold might be ok. My dealer's parts department manager tells me that all parts (and fluids) are linked to a car's VIN. Have the parts department look up the part number for the intake manifold for your car based on the car's VIN.

If the part number on the computer screen agrees with the part number on the manifold... Well, that's one thing. If the part number is different then I think the right manifold should be installed.

Now it could be the wrong manifold was installed by a previous owner or a shop he took the car to, though why the manifold was touched at all is a puzzle.

Or the manifold part number was changed when Porsche changed (upgraded?) the manifold, maybe to address the misfiring symptom. The dealer's parts/service manager or one of the senior techs should be able to tell you if the manifold was upgraded.

In either case the manifold wants to be installed sans any leaks of any kind and any hoses and such checked for damage or age or incorrect installation and this includes routing.

Sincerely,

Macster.

Macster

It is possible that a bad MAF could result in no MAF related error codes. I also point out that there are error codes -- misfire related -- which could arise from a bad MAF. The MAF is a complicated piece of electronics and under some failure conditions can deliver incorrect values but with nothing to compare these too the DME may not flag a problem.

You have IIRC eliminated most other possible misfire causes and absent any other error codes (other than the misfire codes) that could point to a VarioCam problem or something else the MAF has to come under suspicion.

You can try cleaning it. My experience is they don't get dirty. I've driven over 100K miles with no MAF problems so dirty is not something these things get as long -- and I must stress this -- the stock filteration system is in good working order. If you run an aftermarket air filtration system....

You can also disconnect the MAF from the engine wiring harness, clear any codes to reset the long term fuel trims and other things back to their defaults, then drive the car as you did before to see if the misfires return.

If at any time the engine starts acting up, making noises, and so on, shut off the engine and get the car to a qualified shop for a professional's diagnosis.

Sincerely,

Macster.

utkinpol

great tip about disconnecting MAF - it switches ECU to 'default' timing map and it is a simplest way to check if you have any issues related to that. OP - i assume you also made sure your air filter is new and there are no issues with air flow?

997_rich

remember misfires can mean something wrong with the coils/electrics or they could mean that there's something wrong with the mix or timing. If the ECU gets confused by bad data from The MAF, O2, cam/crank position sensor it will fire the plugs at the wrong time or with a poor A/F mix. This would also cause misfire codes.

My point being: misfire codes do not necessarily mean that there's something wrong with the ignition system. In fact, I would say it's unlikely that it's an ignition problem since you have random issues with every plug.. unless its something like a bad ground at the engine.

You might want to make sure you have a good ground at the engine. there should be little to no resistance between the engine block and the negative terminal on the battery.

gio_73

i will defintely try disconnecting the MAF once my manifold is back on. It doesnt cost anything.

The last time i asked the dealer to switch out the DME, they kept it for 3 weeks and didnt touch the car.

I am told the right amount of power is getting to the spark plugs, and the ground is good.

As for the manifold, my vin number brings up a 997 manifold. This is why we asked questions. We've decided to stop questioning this since the fittings and harness match.

Question of the day: Since the injectors were out, we had them inspected by a specialist. At first glance, he said it was bizare that these injectors had no filters.

i truly appriciate the attention from all of you... It makes me proud to be part ofthe Porsche community. And i need the encouragement since my first Porsche isnt as good experience as i thought it would be.

Cheers!

xxxreme

Any update on a solution to this issue?

I just picked up a 05' C2S and have been having the same issues. I had the DME programmed with the updated software and still had the same CEL show up reading a misfire in all cylinders.

I just had all the plugs replaced and had a few vacuum leaks fixed which made the car run smoother but about a week later, the same issue has arisen.

I would hate to run down the same path of replacing coils, cam sensors, etc only to not have the issue resolved.

Any updates would be greatly appreciated!

McCulla

Oh man, xxxreme! At the risk of making you freak out, I chased this issue for 4 years and nearly $15K! Everything from changing the lifters (about $5K) to changing variocam actuators to reprogramming DME to air-oil separator, on and on and on. Probably 20 times in the shop. Probably 60 days out of service. Interestingly, after the AOS replacement, the CEL has gone away for the longest time to date. I would frequently trip the CEL on cold start if I let the car idle for more than about 10 seconds. I was very fortunate that I purchased an extended warranty for the car when I bought it (05 base car, I got at 25K miles). I got the same CEL you have, random misfires on all cylinders. Macster has an amazing rundown on the potential causes of this issue, do a search. I'm sure I posted a dozen times whining about my problems to the forum! Sorry to relate this story, I'm just relating it so you know it's been a problem for others here. Good Luck! (Find a good, trustworthy shop)

xxxreme

Thanks for the quick reply. You may have hit the nail on the head with the AOS needing replacement. I have noticed a puff of smoke at startup intermittently. I have also heard the "whining" sound from the motor occasionally, usually when I'm pulling up to a red light and throw it in neutral. It sounds like a whining humming noise which gets quieter as it idle's longer.

Thanks again for all the suggestions, luckily I have a trustworthy Indi who I've been emailing back and forth on this issue. I think a good cleaning of the MAF is in order also.

I'm also searching for a stock air box as I hear the K&N air filters cause more headaches than anything else.

nuccio

Hi guys. I have been troubleshooting misfire codes and oxy sensor codes for ages. I will cut a long story short. After replacing many known culprits I purchased a $50 smoke machine and pumped smoke into my 2001 carrera intake and Presto! Significant smoke emerged from all 3 LH injectors where they go into the intake plenum.
I replaced all 6 oring seals on that side with the engine in the car. A very difficult job but having a hoist helped a lot.
The car now has never been quieter and smoother. When starting in the morning it just purrs nicely. The old o rings were soft and flat. Don't know why.
So thanks to every one that has helped me on this forum. Hope this helps in your own trouble shooting.
Also, just for info. I carried out the replacement of my IMS bearing and installed the technofix direct oil feed. Nice kit. My dual row bearing was like brand new when I took it out but I have peace of mind now.
Cheers

xxxreme

My independent used a smoke machine to locate and fix several vacuum leaks in my K&N intake and a broken vacuum line. Even after all that, a week later another CEL popped back on indicating misfires in all cylinders again.

I ordered a stock intake since my independent recommend it (K&N was put on prior to my ownership). A few weeks ago, it had rained and the roads were wet. As I was getting on the on-ramp, I accelerated hard through first and second gear. This caused my traction control light to come on (as it should) and after taking it near redline in RPM's, suddenly, my CEL went away and has been gone since then.

I ran a bottle of Seafoam through the fuel tank and through the engine oil for a week. I then had the oil changed and the car has never driven stronger! I just returned from a 275 mile trip and no issues and my MPG increased from 12 MPG when I bought the car, to 16 MPG after sealing the vacuum leaks, now at 19 MPG after running Seafoam through the car.

During the oil change, they checked the codes and said it's running fine now and no new codes have popped up besides some trouble with communicating with instrument panel momentarily?

gio_73

I haven't been on here for a while, so here's a long over-due update.

After coming to terms with the fact that throwing money at the problem was not a solution, i drove my car for 2 more years trying to undermine the intermittent CEL. Before this i spend over $4500 on spark plugs, ignition coils, injector cleaning, strengthening the wiring to the ignition, and overall diagnostics.

Throughout my many hours of research, one of the many possible culprits, especially on the 993 forums, was the DMF. The symptoms described in these cases were very similar to those on my 997 (shake at idle, CEL).

End of season 2013, my clutch started slipping a little. At that point, i decided that when my car would come out of winter hibernation, i would get my clutch replaced, along with the DMF and IMS bearing.

Early season 2014, clutch, DMF, IMS bearing and new motor mounts and everything i had hoped for came true! The shake is almost non-existent and it hasn't thrown a code ever since. No wonder why, the DMF and clutch were in really bad shape.

This is still the topic of many of my discussion with friends as to how the flywheel can trigger misfire codes, but in the end, all i know is that i can enjoy the car as it is meant to be enjoyed.

Spoddle

Interesting, I've read that a bad DMF can cause misfire issues. Good to hear you finally resolved your problem. I'm still trying to resolve mine.

Petza914

Where did you find a decent smoke machine for $50 as I'd like to have one? Thanks.