sacman

You are right. The CEL comes back on my way to the smog check station and now i'm tempted to clear the code using the GoPoint BT ODBII reader now. I'm at lost now. All belts (distributor and engine) were replaced, new plugs, new wires, new air filter, obvious air hoses checked. I have until 7/16 to get the car smogged.

QN

Steve Weiner-Rennsport Systems

Failing DMF's can also trigger random misfire codes so if you have close to (or more) than 100K on a DMF, thats one thing to test.

nine9six

Ha, Steve beat me to it...(DMF) Dual-mass flywheel

They certainly can. Coil wires, cap, rotor, coils, ect...anything that transfers spark signal.

fsa

I had cel appearances and 3-misfire codes appear recurrently after fan and alternator belts were replaced with Dayco, not Porsche. Are your belts oem?
This stopped when swapped for Porsche belts. Steve has written about this on this Forum.

nine9six

See OP post #12

pp000830

I Don't get too disheartened, I am sure it is something very simple, did you run the diagnostic codes. Knowing what the code(s) was should point to your problem directly. Also clearing all your codes won't make the problem go away so there is no point in clearing the code as it will result in resetting your readiness codes.

pp000830

Would he be experiencing a pronounced rattle when shutting down the engine if this is the case. If not I understand the test is rather easy by connecting to the flywheel sensor and observing erratic signal timing.

sacman

Thanks for the encouragement. This is what I hate about OBDII and smog in california. The codes I got before the belts change were P0302, P0301, P0305, P0304. Now, I'm getting P0302. I do have a Sachs clutch kit (clutch and pressure plate) ready to go but i'm dreading the cost or the time if I have to diy. I bought them 2 years ago when I notice a ratting at idle from the shifter ****.

QN

Steve Weiner-Rennsport Systems

Not necessarily, no. Misfire codes occur long before it becomes damaged enough to rattle.

pp000830

Since your codes are random and from multiple cylinders, I would go ahead and have the flywheel tested:
Dual Mass Flywheel - This is a very very uncommon issue. - IF your car seems to idle a bit too rough and you have been experiencing:
 The check engine light and;
 A reoccurring non-cylinder or;
 Multiple named cylinder “emission relevant misfire OBDC code.
AND you have addressed the other less invasive sources of this such as:
 Run the quick, unplug-the-primary-distributor, belt test,
 Verifying there is not a vacuum leak on the engine,
 Cleaning the idle valve,
 Replacing the distributor caps and rotors and,
 Addressed any cylinder specific reoccurring misfire codes, wires, plugs, and injector (done after the items above and a clearing of the codes with the misfire code still returning).
You may have a problem with the dual mass flywheel (DMF).
I am told the litmus test for a failing DMF is to use the PSTII (Porsche tool), put the car in the air and with the car in gear, read the speed sensor directly. I'm told that it will rapidly slow and speed up out of sync with the engine RPM. Also LuK offers a DMF testing tool that physically tests the flywheel once the transmission is removed.

IainM

Have you got good fuel pressure? Maybe a clogged fuel filter or pump in early stages of failure? Possibly DME relay?

For the drive cycle you need to be 25-75% tank level for EVAP to set.

sacman

I double-checked the service history and there's no record of DMF replacement. I'll probably have to take it to the shop for this.

QN

pp000830

I would have it tested first before committing to the big expense of dropping the transmission. Be aware on a 993 one does not need to remove the engine to do a flywheel or clutch. Some shops will charge labor hours for this. Also if you have never replaced the power steering belt it is easy to get to with the transmission out. Also, inspect the wire insulation to the secondary air pump as it becomes brittle from heat. The wires are easily replaced if they look cooked. Two of the very few while-you're-in-there items I would go along with.

sacman

Just a little update and I'm getting more clueless on the cause of the CEL due to misfires. I put a can of Techron and a can of liqui moly jetron in the tank on the way home from work yesterday. Today, I took it on a little road trip of 400 miles roundtrip. The tank was 1/4 full when I filled it up before heading out. As soon as I got on the freeway, the CEL went off and it stayed off until I got to Carmel, about 200 miles from Sacramento. I gave it the italian tune up along the way pushing it near 6000rpm. However, on the way back, the CEL stay ON until I got near home then it went off and back on within 10 miles. Issue like this where there's no clear debug steps are driving me bonkered being an engineer. Yes, I am ready to do a full clutch job to address the possibility of DMF being the culprit but not knowing exactly where the problem starts is just mind numbing. The thought of dealing with this every 2 years before you can register and drive the car took the fun out of the ownership. Sorry for the rant. And yet, I love every minutes of my road trip.

pp000830

Have it tested first, it's a non-invasive procedure and should only cost a diagnostic charge to have done. Did you clean the idle valve?