iliasgk74

my 997_4s_mod2006 had misfires and i changed my ignition coils(all of them).
after one week i have again misfires in 3 cylinders (4,5,6).
i start the engine again and have no problem.
then after a ride i used durametric ,erase faults and log misfires in all cylinders and in "Ignition counter misfire detection"
in all six cylinders the result after a quick ride was 0 and in "Ignition counter misfire detection" was from 4 to 2990!what that means?
also mass air flow was 60 to 80 and a few times up to 180.is this normal?

any idea what is going on?
2000km ago i changed my sparks in porsche!

thanks in advance!

atr911

Since they're all on one side it sounds like a coil even though you've changed it. I might suggest running the durametric under real time values and monitor it for misfires.

Is the car running like crap?

Another possibility may be poor gapping on the plugs but that's unlikely considering 3 of them are bad. (To be honest, I'm not sure the plugs you used needed gapping, if it has more than one electrode, they don't).

I too, am curious as to what acceptable numbers on the MAF are. Many cars suffer from decreased performance because of a dirty/malfunctioning MAF. Wonder if the shop manual will have info...

What are the actual OBD codes coming up?

mobonic

change ALL ignition coils!

If this does not work, change all spark plugs again ( I did this too) the plugs cost less than another hour of labor and is a easy change when you are doing coils.

If this does not work it could be a problem in the timing and or top end...

Macster

What are the error codes? P0304, P0305, P0306 and possibly P0300?

If all misfires are on one bank this suggests (with an exception or two I'll note below) the problem lies with one bank.

Generally the last thing touched is the first thing suspected so I'd want to know the new plugs (changed 2000km ago) are the right plugs -- just because someone shoved the new plugs in boxes across a parts counter to you doesn't mean they are the correct plugs: the person could have grabbed the wrong plugs, the plugs could have been in the wrong drawer, or the wrong plugs can have been put in the right boxes -- and they were installed correctly. This also includes the each coil pack securely attached to the engine and to the plug.

(I had a misfire develop with another car and the cause was traced to a loose plug lead at the plug. It took several thousand miles of driving *after* the plugs were replaced (at a dealer in Salt Lake City) for this misfire to appear.)

If the plugs and coils eliminated then fuel supply to that cylinder bank suspect. A fuel pressure and delivery check of that bank's fuel supply should be made.

Of course a test for an intake air leak needs to be done to eliminate that.

Another possibility is the Variocam actuator for that bank is acting up. If it had failed chances are there would an error code, but if the initial stages of this failure are happening maybe not.

Lastly, I came across a Boxster owner whose engine was generating misfires all on one cylinder [added] *bank*. Various things were checked and found to be not at fault.

Finally, and I don't recall what prompted him to do this, he replaced the MAF, and the misfires went away.

So, one possible test is to clear the misfire error codes, disconnect the MAF at the engine wiring harness. Do not remove the MAF. Then drive the car as you have been and see if the error codes come back.

Be sure to give the codes plenty of time. If they were taking miles of driving to come back before, give them the same and more miles. Just a quick run with the engine cold down the end of the block and back is not sufficient, unless the misfires were appearing in this short test drive before.

One more thing: While the cause of the misfires might be something relatively benign, plugs or coil packs, or MAF or even fuel supply, it might be the early warning signs of something more serious. I'm thinking something related to the camshaft drives or VarioCam system.

So, you have temper your attempts at self-diagnosis with the concern that continuing to run the engine to try to eliminate various possible causes subjects the engne to more serious trouble, possibly even damage, if the cause proves to be say the VarioCam system and this finally fails.

Sincerely,

Macster.

iliasgk74

thank you all for the answers!
i have changed in porsche center sparks 2000km ago.
Now i changed all the coils.
in durametric last run gives me faults in real time in Ignition counter misfire detection and not in each cylinder.
i 'll go for sparks and new maf to see new results

iliasgk74

mass air flow was 60 to 80 in real time in durametric and a few times up to 180.is this normal?

Macster

I'm not familiar with the Durametric product.

I'm most familiar with the OBDII error codes the engine controller generates and logs and are read by an off the shelf OBDII code reader/data viewer. For misfires these are P0300 to P0306 or P1113 to P1119.

Briefly, my info is the Ecu constantly monitors the acceleration imparted to the flywheel by every power stroke of every cylinder, in spans of 1000 revolutions, and in the case of detecting possble TWC (3-way converter) damaging misfires (the risk of feeding raw gas to the converters) every 200 crankshaft revolutions.

If the acceleration from a cylinder's power stroke over a span of 1000 (or 200) crankshaft revolutions is below or above a threshold a fault is recorded.

Additionally the CEL is turned on and left on when the misfire rate is above the threshold at which emission limit values are exceeded during two consecutive driving cycles ((USA OBD II) or 3 consecutive driving cycles (European OBD II).

If the misfire rate could lead to damage to the TWC the CEL is flashed.

If the misfire rate is longer reached during the 1st trip the CEL is turned off. If the rate is reached during the next trip the CEL is flashed. If the misfire rate is no longer exceeded the CEL is left steady on.

The Durametric might (as I mentioned above I'm not familiar with this product) might be displaying the on-going misfire counters. These can accumulate misfire counts, misfires which are natural under some conditions, which is why the Ecu checks for the misfires over a span of time (represented by crankshaft revolutions, which of course depending upon the speed at which the engine is running means the time varies).

Only if this misfire count exceeds the threshold deemed by the Ecu to be indicative of a real misfire problem and pontentially damaging to the TWC does it turn on and possibly flash the CEL.

If you are getting these working misfire counts from the Durametric tool you mght be chasing phantom misfires. They are real, but their number has not exceeded the threshold and advanced into misfire counts worthy of triggering a CEL, steady or flashing.

If I'm right of course about what the Durametric tool is providing you, or what you are asking it to provide you.

So, again my question is what OBD II error code(s) is (are) being generated? Does the CEL come on? Does it flash?

Sincerely,

Macster.

iliasgk74

the cel come on and flash when engine is cold.
then i turn off engine and start again.no cel but obd errors P0300 to P0306 as i remember

Macster

Ok. Let's see...

Is fuel tank empty? Could it possibly be empty? If so fill gas tank, clear error codes and road test vehicle.

Are there any O2 sensor faults? If a sensor ahead of the TWC (3-way converter) experiences a short circuit (to IIRC B+ or ground) the mixture can become too lean or too rich and this can cause misfiring. (Since the CEL flashes the misfire is probably a too rich condition.)

The recommendation is to correct the sensor fault (replace) or if you want swap left and right sensors and see if the fault follows the sensor.

If you replace the sensor of course clear the error codes and road test the vehicle.

If the error does *not* follow the sensor -- if you opt for the swap sides course of action -- then the fault likely lies elsewhere. It is not a sensor fault.

Then other possible sources of the problem are: fault in the ignition system (coil packs or possibly spark plugs); fault in the injection system (dirty, contaminated, or even worn injectors); flat based tappets (valve lift fault); mixture too rich (duh); or mixture too lean (double duh).

Mechanical causes: valve lift fault. Let's leave this alone for now. If you need this info ask and I'll reply with it.

Camshaft control times adjustment and VarioCam does not switch over completely: Same comment as above.

Check for air leaks in intake system.

Check spark plugs. Gap: 1.6mm +/- 0.2mm.

Check spark plug connectors.

Check coils: Measure resistance between Pin 1 and Pin 15. Reading should be 0.3 to 0.7 ohms at 20C.

Check all spark plug/coil connectors for proper contact (no loose connections) and corrosion.

Check fuel pressure. Engine off pressure should be 3.8 +/- 0.2 bar. Engine idling fuel pressure should be 3.3 +/- 0.2 bar.

The closure cap on the fuel pipe is removed and the seal or sealing ring should be replaced. Tightening torque 2.5 +/- 0.5Nm.

There are other tests but some most appear to require a PST2 (Porsche diagnostics computer).

If you want send me a PM with your email address and I think I can make a PDF copy of misfire trouble-shooting and if so I'll send you a copy to refer too.

Otherwise, I'll have to type in pages of test instructions.

Sincerely,

Macster.

utkinpol

at idle maf shold be in area of single digits - 5-6 or so, at open throttle - up to 200. i do not have my aim videos riht now so cannot confirm for sure but it does change a lot.
it should not 'dance' too much if your car sits at idle. if you have constant idle RPMs like 600-750 but MAF 'dances' - take it out (you`ll need torx bit) and wash it with maf cleaner aerosol. as a rule of thumb give it a bath every time you change air filter - applies to any car brand.

iliasgk74

what can i say!
many thanks!
i''ii send you my mail

Spoddle

Bringing this thread back from the dead to thank Macster. I just ran into this fault on my 997 and am hoping to diagnose it using your posts.

Upon startup the check engine light came on, flashed, then stayed on. I'm hoping it's just bad gas.

Bosch Digital Motor Electronics Motronic 7.8.1

Fault Codes
P0300:Misfiring checksum error
P0301:Misfiring cylinder 1
P0303:Misfiring cylinder 3
P0305:Misfiring cylinder 5

atlast911

I had these same fault codes after the car sat for 1 month without starting. The idle was rough at start and there was a noticeable valve tick. My Indy said the lifters "pump down" when they sit so long and driving it should clear the code, it didn't so I did with the Durametric. The car runs perfectly. My question is will the code stay on until the shop (or you) clear it? Once I clear it and it doesn't come back does that mean everything is cool? Again the car runs perfect.

Spoddle

I'm still troubleshooting this exact issue and am picking up my car from my local indy this evening. Time will tell whether their solution fixed the issue.

I've cleared the code in the past and had it come back upon cold start. So far I've replaced the following components.

- Spark plugs + coil packs
- MAF
- Crank position sensor (replaced by indy)

My local porsche dealership also suggested that I replace the valve lifter solenoids.

atlast911

Does anyone know if the CEL and fault codes can clear on their own or does they need to be reset?