AWDGuy

You may have introduced air bubbles, but that wouldn't have anything to do with those codes. Fill her up and drive around with the vent valve stuck open for a drive.'


Check all the connections going to the variocam sensors. Double check all vacuum lines near the AOS.

msteiner805

Brief update:
I started lightly tugging on some of the vacuum connections, and, in the diagram below, I pulled on point B and it immediately came loose from the point attached at the back of the engine. So I have to figure out how to get to that vacuum connection....

Also, I pressed on the vario cam solenoid connection and it was hard to tell if it "clicked" a bit, or, if the noise was some plastic bits falling off. This connection is likely in need of replacement as it was brittle and caked in oil.

msteiner805

Just wanted to give everyone an update. I found quite a few issues that I then needed to dive into:

- In order to get to the disconnected vacuum line, I took off the throttle body.

- Upon cleaning the throttle body, I took off and tested the Idle Air Stabilizer Valve, and, it was completely stuck open with tons of caked on grime. I couldn't see the flap, and, it wouldn't move at all with applied voltage.

-After many Qtips, MAF cleaner and WD40 the valve started operating when I applied Voltage from a 9V battery.

- Upon inspecting the oil filler tube, I found a fairly large crack. When I bent the tube to get a better look at the crack, the oil filler tube broke completely apart! So I had to remove the alternator and pull out the oil filler tube LOL.

So now I have new parts arriving today and this should get me further along the rich/rough running debug process!

Thanks,
Mike

dporto

Ah, the merits of 15 year old plastic that's been through thousands of heat cycles! Good luck with your fixes

msteiner805

Thanks!

Another update.

Last night I replaced the oil filler tube and re-installed the throttle body with all new seals as well as a cleaned out and functioning IASV.

Same problem LOL. The car starts up well, sounds good above 1000 rpms and then proceeds to dip down below 700, then 500, then it starts to stumble, feels rough, idle not constant. Smells pretty rich as well. Unless I open throttle it feels like its going to cut out. I didn't run for more than 15-20 seconds, but, the issue is definitely still there - but the issue seems more pronounced now. I'm thinking I'm poking at a major intake leak here.

Below is how I debugged the vacuum leaks in my 928, will this work for the 996 intake system?

I used an adapter (made from hardware store parts) to pressurize the intake and listen for escaping air. It worked really well for the 928 intake. I think the sizes are about the same, so, in theory, I should be able to pressurize the 996 intake and hear leaks, right?

The picture shows the 928 throttle body off the car, but, the technique worked the same with it on the car. With the 928 all the air/oil stuff is hard to get to with the TB on.

msteiner805

Went home for lunch today and decided to try something... I disconnected the MAF. With the MAF disconnected, the car idled higher, but, it actually ran smoother!!!

So I took the MAF out, cleaned it out, nudged the pins off center a bit (this is to make sure there is contact force upon connecting) then reinstalled. I then cleared the CEL codes via the ODB port and started the car.

At first the idle was moving around, bumpy, but, the idle was less lumpy than before. Maybe the ECU was trying to find the right settings? After a few minutes, it started getting a bit better. After 5 minutes, still no CEL light, and it got pretty smooth. Engine temp was climbing the whole time.

I let the car idle at temp for another 10 minutes and it was a smooth and fairly consistent idle. No CEL.

Revved a few times to 3k. No CEL. Engine even sounded decent....

So either the MAF cleanse fixed this, or, its a cold-engine problem. Anyway, a result!

Not sure what else I can start looking at for the time being...