some dme assistance, very odd issue
 

Gents,
I have a 99 boxster with a 3.2L from a 2001 boxster s. The car runs the standard 99 5.2.2 dme and associated wiring harness with the new motor. Everything was plug and play, only change was the addition of the resonance flap in the intake which was wired as per the pelican instructions.

The dme was updated by softronic for the swapped engine.

The car runs good, no check engine lights or driveability issues generally. Revs to 7200 rpm when a standard fuel cut limiter is introduced.

After exactly 30 minutes of run time, however, the car will start to break up at about 6000-6200rpm and will not rev through that rpm. With this exception it runs totally normal otherwise. If you stop, turn the engine off, and restart, the car has no issues until another 30 min.

Battery voltage is good
Maf flow voltage appears normal and the maf was swapped for a known good unit with no change
Maf is in the 3.25" sampling tube from a 987
02 sensors new and reporting fine
Crank sensor new
Fuel filter new, no apparent fuel pump issues
Engine coolant temp reporting normally
Engine oil level reporting normally
Hitting the lower rev limiter has no effect on overrev counter
Tps replaced by known good unit
No apparent vacuum leaks as per smoke test

Im absolutely befuddled and it leads me right to the Dme work but scott at softronic denies its a dme or software issue.
The indy i occadionally use seems to be out of their depth and not super willing to help.

Anyone have any ideas?

Thanks very much

well, the odd thing is the *exactly* 30 mins issue. perhaps the car is having issues transferring short-term fuel trims to long-term fuel trims? can you log your trims and see what they are doing? the problem then shows up at 6000 rpm because the car will not go into open-loop?

or, the problem at 6000 rpm is a variocam issue - can you actuate your cams w durametric?

Ltft seem normal, stft fluctuate as usual.

Cam deviation is under 2 when warmed up havent tried actuation. If it was variocam u would think it would be throwing a code but i can try. Why would that happen right at 30 min though?

Last time I looked, a 2001 engine ran a 7.2 DME, are you sure that isn't your issue? The 7.2 is much more complex than the 5.2.

not sure - perhaps there is a warm-up period tied to engine temp which takes about 30 mins to get to? you mention the problem on restarts - cold starts also?

really, once someone has been in messing w the ecu then all bets are off. the fact that you are running a 987 maf holder means they have done some black kung-fu in there, as others have been told by them that you cant change the maf conversion map (in a 7.2, anyways; perhaps more flex in a 5.2.2?).

can't think of what else works on a timer to make it screw up at exactly 30 minute - secondary air system perhaps?

The pre 2002 3.2 motors still use the same variocam units so the whole thing is plug and play. Its pretty much the same motor as the 99 carrera 3.4. Reading all the swap guides im told this shohld not be an issue.

Happens after cold starts and warm restarts so that to me rules out a temp issue. The 5.2.2 dme also runs the 3.4 on the 99 carrera with a 3.5" maf tube so definitely able to utilize a bigger sampling tube. I believe there is some sort of checksum or maf scaling error that causes the car to enter some sort of limp mode but no one seems to know. Id love to send the dme back to softronic for a look but
This was not presented as an option. Kinda sucks aftwr paying 1300 bux for the tune

if you like, pm me your email and i can send what i have on the bosch FI system; perhaps there is something in the literature about a timer or countdown, or the scheduling of info writing or something.

Sputtering at high rpm when the engine is hot is a classic fuel delivery symptom.

It might be worth the effort to test the fuel pump when hot.

Other thoughts: injectors, injector wiring, debris in air intake/snorkel.

Just curious why you didn't put a matching DME and immobilizer (with key fob) from a 3.2 in your car when you did the swap? I think I would try the correct DME first before spending a ton of money on parts and trouble shooting. You should be able to source a set for around $500. Of course, I suppose the immobilizer wires might have changed from 99 to 01 but easy enough to test if you order parts that can be returned.

its an entirely different DME and harness.

The 5.2.2 dme can easily run the larger motor, given that its used on a 3.4L carrera from 1999. The ability of the DME to run the engine is a non-issue.

You might be able to extract some useful information on what the 5.2.2 is actually monitoring and doing each cycle by reviewing this 5.2.1 diagnosis PDF. I found it interesting to be honest - about 1/2 way through the PDF.

https://www.nanocom-diagnostics.com/uploads/downloads/Bosch%20Motronic%20M5.2.1%20EMS%20ECU%20Guide.pdf

It's not plug & play to connect a 5.2 DME, 99 IC, 99 BCU / alarm system and a 987 MAF to a 01 3.2S engine.

They have done some eletronic and software mods for shure. That often means that you don't get an DTC because the DME/system gets fooled by intention.

What transmission do you have in the car? AT, MT6, MT5? If AT, that could also cause problems.

Regards, Markus

no no,
lets be clear.

99 everything, including the maf (not a 987 maf). Think of the motor as an upsized 2.5L with a intake manifold resonance flap.

The SIZE of the maf sampling tube has been increased, but that is adjusted with maf scaling.

Tranny is a MT 5 speed.

The car runs perfectly fine for 30 minutes, and runs perfectly fine up to 6000rpm after 30 minutes, and then runs fine after shutting it off for another 30 min.


If the car didn't run, or ran crappy from minute one, Id think a lot of points are valid.

Will review that document porsche-eh.

Thanks everyone for your comments.

Just to be clear, is this 30 minutes exactly or around 30 minutes? When you say shut it off and it runs fine, you mean you can just cycle the key off and right back on and everything is fine or you have to shut it off for let's say a minute or 10 or what?

I cant tell you 30 min to the sec, but its not 28 and its not 32...repeatably.

No wait time necessary, key off, no delay, restart, problem gone for another 30. So its something where the memory clears on a restart

One other quick question, does this happen instantly or does it come on slow like it starts breaking up at 6500, then won't go over 6?

instant as if a switch is thrown.

Well, it certainly pretty much eliminates anything mechanical and it must be in the DME. I don't know it well enough to guess what comes in after 30 minutes but perhaps you can do some logging to figure it out. Does the EVAP solenoid open or something like that and it tries to purge the tank pressure ??? I have no clue but logging all parameters would maybe point to something that opens or changes at that interval. There are some codes that cars won't throw till a 2nd or 3rd drive cycle or a drive cycle that is over a certain length of time, I don't know what that is on the Porsche as I am a mechanic but not Porsche specific or that familiar with it.

https://www.youtube.com/watch?v=Zv3wx-6bAgE&feature=youtu.be

video of the situation.