onspeed

put back the venturi lines and ISV... still not working. ISV is working cause i can feel it vibrating when the key is turned to the ON position. and the venturi lines aren't cracked or anything. going to test AFM now.

Adonay

That does not mean it works. My ISV was broken and i could not tell other than guess based on fixing everything else. My car would die every time i let off throttle after the ISV change no problems the car can idle.. The ISV may also have a huge vacuum leak btw

onspeed

Interesting. I've ruled out the AFM. Turns out my dad put in a MAF sometime ago... it's a pro-flow pft77 - which i searched for and apparently pro-flow is now autothority? I always had a feeling he did some modifications to the car... maf + a VDO boost gauge i found in the garage a while back. guess that explains why i was dead even (on boost) with my brother's 6speed ls1 trans am? I couldn't find any vacuum leaks with the ISV or venturi pipes, i just blew into them while holding the other end close. So either the ISV is broke... or DME maybe? possible water got into it and screwed a solder joint?

black residue coming from the tail pipe.

jmj951

The black soot out the exhaust is just from running rich.

Going to be really difficult to diagnose with an aftermarket MAF (that might not even be supported anymore). Without extensive diagnostic experience on this car, you're probably going to need a working 'donor car' to start swapping parts. Good luck, I'll be following the thread, I'm interested to find out what the culprit is.

When my TPS went out, it idled just fine, but stumbled badly on acceleration.

Have you tried the steps listed on Clark's Garage for rough idle?

onspeed

pulled the DME, some evidence that water was once in it. going to clean it up a tad, see what happens. i've already checked through clarks-garage for possible causes. from what my search tells me, pro-flow makes nearly all 951 mafs. supposedly even lindsey's. the lindsey unit looks identical to mine actually... pro-flow has been around i guess. think they're called pro-m now actually. but in any case, the car has run for years with this maf, only 45k, but the maf was installed in like the early 90s.

jmj951

That sounds more promising, though even the Bosch MAF's in 996's fail in considerable numbers so I don't know how reliable MAFs generally are in the long-term. But my 24-yr old AFM in the 951 is still working. I had to replace the MAF this year in my 11-yr old 996 and found in the 996 forums that it was not uncommon. I don't want to lead you on or get you scope-locked, but the MAF failure in my 996 wasn't severe yet, and it still made the car idle rough and run rich (some white smoke out the exhaust, CEL code pointing to MAF), and those problems disappeared after changing the MAF.

onspeed

will keep that in mind.

cleaned some corrosion off the DME board, car idles a lot better now. no more sputtering or anything. however, same symptoms occur when i try to give it gas.

uploading a video. when i just barely open the throttle, the car almost stalls out. and as i give it more gas, it'll rev, but not freely or quickly as it's supposed to. also, maybe i haven't heard it in a while, but something sounds different about it.



those few revs, are at maybe half throttle. it should rev all the way up with that much gas, quickly too. the last part where it dips down a lot, is with me touching the gas as lightly as possible. just barely turning the TPS. i don't get it though, ohm tested the tps as clarks-garage states, checked out fine. plus this is a new (used) one that i put in after it stopped working a year ago.

onspeed

i'm stumped. started the car again an hour later, back to running like crap. i didn't see any bad solder joints on the dme...

at "idle" the boost gauge stays about 3/4 the way to the middle... should be at .4 right?

onspeed

waking up early tomorrow to check the following:

DME temp sensor
injector leakage (not sure how... maybe i can disconnect one at a time and see if it runs differently from another or something)
fuel return line (read that if there's a blockage at the level sender or something, it'll cause high fuel pressure.. or dampener failed? but it was replaced just a few years ago)
connect a vacuum hose directly to FPR
reference sensor.

Grandpa#3

Check out the link below.

http://www.texasblake.com/porsche/index.html

Cheers,
Larry

onspeed

good read. didn't see anything on there that could help me out though (beside service manuals, but i already have them). Is that guy on the board? I know we have a few active houston members... myself included.

onspeed

found the problem. jmj951 - you almost called it. MAF sensor was broken. the inside plastic had become brittle and broken it, caught a large piece right by the turbo inlet, i assume some smaller pieces hit the turbo... hope the propeller isn't screwed. its from autothority from 1994, came with chips. sending it in to pro-m and they're gonna get me going again. temporary installed the old AFM setup, found it in storage, and car "ran." obviously the AFM isn't compatible with the MAF chips, but i started her for just a few seconds, ran MUCH better... no smoke everywhere. i have the stock dme/klr chips, but i think i'll just get started on the clutch while pro-m fixes me up with another MAF.