2002 S Idle/Stall Problem

earossi · 04-07-2013, 05:47 PM

I had an AOS go bad on me and decided to not only replace the AOS, but to go ahead and tackle the IMS bearing replacement that I had planned to do all along. The job ended up spanning over several months, due to not being able to work in the winter on the car. If weather had not been an issue, we would have spent a couple of weekends knocking out the punchlist of work that also included degreasing the engine, and changing oil and filters.

The good news is that we finished up on all the mechanical work this weekend. The car fired right up, but I have an erratic idle. Treating the throttle with "kid gloves" I can get the car to idle at 900 rpm smoothly. But, when I blip the throttle, more times than not, the car will not return to idle......it just dies. I was able to drive the car and it seems fine when you are on the throttle; however, if you let up on the throttle, it sometimes retuns to 900 rpm, but mostly it will stall.

Can someone point me in the right direction of things to troubleshoot to fix this issue? There are no "abnormal" sounds from the engine. Just the reluctance to idle much of the time and the stalling. The engine is responsive and makes good power.

Weve been at it for two days now, so will quit for the night, but would like to map out a path to solve this issue. I'm assuming that it is an electrical issue. The car has been sitting for most of the winter waiting for the hour here or there to work on it, so the fuel is old. Though I did not recharge the battery, the car started as normal on the first try.

I'm just tired and at a loss. Any help would be appreciated.

earossi · 04-08-2013, 05:04 AM

I'm still in need of help. Has anyone ever dealt with and solved these types of issues?

The Radium King · 04-08-2013, 07:09 AM

crankshaft position sensor? therwise, check vacuum. failing aos can cause oil fill tube to crack and affect vacuum. any codes?

thom4782 · thom4782's Garage

Three or four other possibilities come to mind: throttle position sensor, dirty throttle body, vacuum leak. I'd look for a dirty throttle body first given the AOS failure.

earossi · 04-09-2013, 05:07 AM

As you can see in the attached photo, we found a hose that had slipped off the flange of what we believe is the throttle body. So far, my son has been unsuccessful in getting the hose to move back onto the flange. We have removed the clamp seen in the picture and attempted to force the hose into place. For some unknown reason, Porsche has made this hose extremely difficult to install. Any ideas why this would be and are there any tricks to get the hose to slide onto its mating flange?

The Radium King · 04-09-2013, 06:31 AM

i've heard of folks making a 'come along' out of wire and pulling them together in that manner. ie, a loop around the pipe to a loop around the throttle body and back. tighten the wire and they pull together.

funi · 04-10-2013, 12:19 AM

I greased both the flange and hose loosened clamp almost all way up and used a heat gun on hose (on low) and managed to use a pry bar to get mine back on good luck

earossi · 04-10-2013, 05:27 AM

Thanks for all the responses guys. I keyed on the suggestions made by Radium and funi, and used a heat gun to warm up the hose. It's still cold in Idaho, so the heat gun was the solution. A couple of minutes of heat,and the hose became noticeably more flexible/stretchable, and the hose popped right onto the throttle body flange. No grease or vegetable oil needed. Not even a lot of force.

Put the clamp on the hose, and fired up the motor.......and she runs perfectly! It is still a mystery why a leak in the flow path between the air filter and the throttle body would cause an erratic idle and stalling, but the car is definitely cured of those issues now.

As my son says (and he is doing all the wrenching)......."I had forgotten just how much fun it is to drive this car!!!"

Thanks to this wonderful forum.

Hatzenbach · 04-10-2013, 06:02 AM

Quote:

Originally Posted by earossi

It is still a mystery why a leak in the flow path between the air filter and the throttle body would cause an erratic idle and stalling, .

Well, because you got no airflow at all on the MAF, which means the whole DME goes haywire

earossi · 04-10-2013, 09:42 AM

Quote:

Quote de earossi

It is still a mystery why a leak in the flow path between the air filter and the throttle body would cause an erratic idle and stalling, .

Well, because you got no airflow at all on the MAF, which means the whole DME goes haywire

My dumb! Did not visualize the flow path. Thanks.