ramans

So I've been chasing a problem for a while where the car seems to run a little rich and if you're coasting down a hill on the freeway it would occasionally stumble when you got back on the throttle. It was intermittent but would happen once or twice a 20 minute drive. Also occasionally you'd get the bucking at very slight throttle like crawling in traffic.

Now it starts okay in the morning but sometimes needs a little slight throttle crack for the first minute then will idle okay, but the above issues are getting worse, sometimes it doesn't even want to come away from a standstill without bogging. After it's sat for several hours at work I go back to the car and it will crank but won't start even with a slight throttle crack. After a minute of trying it'll usually fire up and idle incredibly rough for several minutes then be back to the above.

We tried an idle adaptation before the symptoms got worse, I pulled and cleaned the ISM it didn't seem dirty, and when I attached it to 12v I could feel, hear and see it moving, although the difference between the two states didn't seem huge looking through the hole.

Next up I'm going to pull the airbox the flap there and the throttle bodies and clean them out and put them back, is there anything else I should be looking for?

I've done a ton of search and reading here the only thing I can find like this is the threads that say ISM and one which sounds similar where the AFM needed cleaning they had the downhill coasting issues I see.

thank you.

540964

Have you changed the DME relay?

ramans

No I have not, but it cranks no problem it just doesn't want to run without encouragement.

ramans

Got another DME Relay the one I pulled out was warm to the touch but no difference still runs like crap. Still wants to stall out going down hill.

I pulled the AFM it looks clean and the door moves nicely and springs back solidly, so I don't think that's it. I'm trying to figure out all that has to come off to get the throttle bodies off, but I can't find an adjustment procedure for the butterfly's in the manual.

It does appear that the idle switch is hit at the very end of the throttle throw and it take nothing at all to come off of it, and in fact the butterflys don't open for another few degrees of movement of the throttle cable. I'm trying to find info now on adjusting this.

Duck

Not to say that your AFM is an issue but the fact the door moves fine is not an indication of how well it is working. Do you have a scantool to check for any faults?

Goughary

I had beru distributer caps once. The heads broke loose and the wires were arching all over the place. Take a look at the caps and rotors. And check the continuity of your wires with a multimeter. Each should read approx 3 ohm

And get a set of coils to swap in. They could easily be your issue as well.

ramans

I did a search and can't find a picture anywhere of what the ISV should look like in each position looking through it. mine cycles but the size of the hole doesn't seem appreciably different, does anyone have those photos or a link to the thread with those photos? I'd love to compare.

onceover

Worth checking if there is fuel in the vacuum line attached to the fuel pressure regulator. If there is, the regulator is faulty and could very well be the cause of your problems.

ramans

Tonight I went in to put the stock chip back in to see if that would help things, unfortunately I didn't notice but I pinched the small jumper block wire (I think it sets the ECU mode) under the ECU when I reinstalled it, and when I tried to start the car it burned the wire way back into the harness. So for now I have a larger problem to deal with. Starting to look for threads on people who've fixed that now...

Spyerx

Crap. Search pelican 911 forum. I read a similar issue there a month or so ago.

ramans

You're brilliant I almost never look there for 964 issues: http://forums.pelicanparts.com/porsc...ring-loom.html thank you!!!

Spyerx

That's the exact thread good luck with fix

ramans

I did not have the time to deal with the wiring harness so I took it over to the guys at Chris' German Auto, and they did a fantastic job, we had to replace the harness but were able to source one from e-bay (it burned up the entire wire and did who knows what other damage). In the process they came across three things which may have contributed to the issue

1) The O2 sensor looked "old" so we replaced it, it definitely hadn't been done when the engine was rebuilt
2) Ditto the cap and rotors
3) The previous harness hadn't had the TSB performed for the AFM

Now that I have the car back I've only had the chance to drive it twice but it has exhibited none of the issues it had before, Idle is consistent, and it hasn't bogged down under part throttle at all. I'll need another week or two of driving it to know for sure, but it definitely feels like one of those did it. I'm guessing O2 sensor, but no way to know for sure.