Temporary ignition stumble type issue

[LanceGT4]

Hi all
I was up in the hills near home today mt. biking.

My 05 Turbo ran fine on the climb up to the 2500 ft. level where we started our ride.
It has 69,000 miles and I have plugs and air cleaners ordered.

After the quick ride, about an hour later when I started up the rig to drive out the engine fired up and then started to stumble. We could not tell if it was ignition or fuel issues. After about 20 minutes of head scratching and wire wiggling we tried to head down. It would stumble along at 4 mph downhill.

No Check engine lights. No idiot lights, nothing to indicate a problem.
After couple more stops and starts whatever was wrong seemed to clear itself. the rest of the drive out, 15 miles of logging roads was OK. And on the highway things were fine again.

(Except for the 2 flat tires the Land Rover LR3 I was with had. Or the drive out to get a lug wrench that fit his after market wheels )

It's a Monday. Any ideas or suggestions? No Durametric until after I get the Christmas shopping done:-(

Thank you to all veterans

[Nostril Cheese]

Check the obvious things like loose intake hoses, plugs to the MAFs, etc..

Could even be a battery starting to go out. They do odd things like that.

Durametric is your best bet.

[MysticLlama]

Did it only do it on this trip, or has it started doing it at low speeds on flat ground also?

[LanceGT4]

Today I got a P0441 code when I headed out for another ride. Purge valve. I've seen a write up on RennTech and one here also.

There have been times in slow traffic that it seems to have a rougher idle than I would like. But it will accelerate and clears as I increase throttle.

The plugs and air cleaners got here today from Pelican. 2 days ahead of scheduled. NICE!
I'll spend the next couple evenings replacing parts and researching the eng. code and purge valve.

Thanks! I'll update after I do the plugs and check things out.

[MysticLlama]

If you're getting it in traffic too you may have the beginnings of a cam adjuster blockage also.

I'm going to post a write up on one of the treatments later this week when I get a chance to take some pics. The basic idea is to shock the solenoids with higher than normal voltage to get them unstuck. Made a big difference on ours.

[LanceGT4]

Plugs and air filters are installed.
Either I should buy a lotto ticket or the belly pans are self cleaning. All thumbs tonight. Every bolt and socket I dropped fell right thru and onto the garage floor!

The old plugs all had gaps of around .035. The maintenance pdf I found on the Porsche site specs the plugs at 1.6mm, about .063 inches. They have been changed at least once in the 69000 miles on the rig. Some of the bushing in the coil covers are missing. I've seen better plugs, but I've seen worse too.

I did find that the eng. brace on the right side has a perished bushing on the frame side. I'll have to inspect the other motor mounts, the clearance to get the right filter cover on is so tight I wonder if the motor is where is should be.

The rough idle in traffic is just not what I expect from a tuned engine.
I'll know more after a test drive tomorrow.

thanks for the advice everyone

[LanceGT4]

The plugs spec'ed in the maintenance pdf ( Bosch FGR 6 KQE is a 4 electrode plug (although I find some images showing 2 electrodes)) are not the ones Pelican uses in their Tune-up kit.
It looks like the Beru Z185 should be gapped at .8mm as listed in the box.
If you can't do it right do it twice. More chances to see if I'm lucky or the belly pans are self cleaning.

[LanceGT4]

On the drive to work today I couldn't tell much difference. But it is a 30 mile highway cruise with maybe 3 miles of city streets.
The air filters were not clogged or even very dirty. The plugs are not the most consistent I have seen. But for an engine with a reputation for using oil not bad.
Slight improvement in mileage, I'll know better after a tank or 2.

I still have a dead spot between giving it gas and pulling a way from a stop. It's not missing or stumbling. More like throttle lag on the electronics.
PSM off or on makes a very large difference. It's like installing a stage 3 chip that reprograms the transmission also. Is that normal?

If I do get this stumble again is there anything I can to at that time? open and close tank filler? any kind of recycle I can do? I would hate for it to happen on I-5 in heavy traffic.
thanks
Lance

[MysticLlama]

PSM off, from what I understand is like sport mode on the newer ones with traction control still on. They have a 2 stage, we have a single.

The traction control, etc. will still kick in, but at a higher limit than before. The shift points and throttle response are vastly different though, quite a bit better. I'm sure it eats more gas too, but at least it's not immediately in 6th at 35mph.

If the stumble is the cam adjusters, it'll likely only happen at idle and very low speeds. From what I can tell, the cams get stuck in such a way that it's like having a big cam at idle that's really lumpy, and the computer can't compensate really well.

If there aren't codes, and it's not super consistent, this would be my guess.

I'll actually run down and take a couple pics right now, I need to reshock ours anyway as the first run didn't quite do it.

[LanceGT4]

@ MysticLlama
I saw your post above mine. thanks for the research. I'm glad this never seemed to happen on my W8:-) 3 trannys was bad enough. That car warranty sure paid for itself.

I have an oil change planned for this weekend. I think I'll try your shock therapy before warming up the engine for the change. or maybe warmup shock and then a short drive to flush anything down to the sump.

PSM on in mine shifts to 6th until about 55, usually. PSM off and any enthusiasm results in something that sounds like PDK and full launch mode. Whee!
I better take it in for a full DE inspection before I find longer on-ramps. They are in short supply here in Grays Harbor. But McCleary east to west bound 8 is pretty fun. To bad about that WSP cruiser that likes to lurk around the next corner.