earossi

I had an AOS failure on my 02 Boxster S several months ago. I decided to not only replace the AOS but to tackle the install of the LN Engineering IMS bearing at the same time. Since winter is not the best time to work under these cars, the job has taken several months to complete. I also did quite a list of maintenance items "while I was in there", including fixing a few oil leaks, and changing oil and filters. I also degreased the entire engine compartment.

The good news is that I completed all the work and the engine fired up on the first try today. Unfortunately, I have an erratic idle, and when you blip the throttle, the car will die when attempting to return to idle. I was able to drive the car, and under load the car sounds and pulls just as it did before any of the work was performed.

When I can get it to idle, it will idle smoothly at 900 rpm. Once you begin to manipulate the throttle, the motor does not want to idle smoothly and will most of the time just stall (no load on the motor). The engine sounds fine. No unusual noises. The IMS bearing that I pulled was fine, but there was some slop in the assembly. The car has about 70k miles on it.

Any suggestions to track down the issues would be appreciated.

gfl

I would begin with the basics- vacuum leaks, loose connector wires, etc. If the MAF connected? I knwo there's another FI/ECU connector that plugs on the back of the throttle body area. But it sounds like a air/fuel mismatch problem to me.

Grant

Davebrossi

Hi There,
I know the Ignition Coil leads are secure on the lower end (at the coils) but one thing that I seem to recall is a lead that ran near the AOS valve. Am I misremembering things? or is there something there I might have disconnected to keep 'out of the way' as it were? Unfortunately the rebuild became more organized only after I'd removed the AOS (Never again!) Sorry for the confusion, my dad there trying to help out by posting the initial query :-)

terbiumactivated

If it was running great before you wrenched on it then the first step is to recheck all that work and any connections you might have loosened, it also tends not to point to a coil unless you disturbed one during the work. The easiest way to track it down is to get the codes read.

Davebrossi

To help me rotate engine during the IMS Replacement I removed the ignition coils. When I initially restarted the car only four cylinders were firing and I found two of the ignition coils not properly plugged in. After that the car seemed to idle perfectly, but when I'd blip the throttle it'd die on me, or let me rev until I let off the throttle, at which point the car would stutter and die. I'll check the breather hoses off the AOS this evening. One thing I do remember being a PITA however was the air intake line that went from the throttle body to the air filter. It didn't seem to fit properly to both ends. Could this contribute to the problem? I've got a Durametric reader on the way, so in the long run I'll run the codes. I'll also check the wiring for the MAF. I'm getting pretty good at pulling the enging covers I think :-)

Macster

All I can add is the time I removed the throttle body in seeking to find the cause of the symptoms that proved to be due to a bad AOS the intake tube was a real bear to get installed again.

I resorted to vegetable oil and a heat gun to soften the plastic just enough to let it slide on the alum. TB.

Check everything but check that intake tube/TB connection twice.

gfl

...of a vacuum leak.

earossi

Well, we found a disconnected hose. See the attached picture for the hose. Having said that, the hose is extremely difficult and does not want to slide onto the throttle body. What is the trick to get the hose to slip over the flange edge? We are going to clean everything up and use a little bit of oil to coat the ID of the hose, but we first tried to force it into place and it was very difficult. Putting the clamp on is another issue.

Does this hose explain the stalling?

Davebrossi

I should also add I did use a very basic code reader which identified the two cylinders tied to the poorly connected ignition coil wires, and a low voltage reading on the MAF

earossi

Putting that hose back onto the throttle body flange was a challenge. Thanks to gfl and Macster for suggestions. A couple of minutes with a heat gun did the trick. It's still cold in Idaho, so the heat successfully restored flexibility and "stretchability" to the hose, and it slipped right over the TB flange. Did not even take a lot of force. I am still wondering why Porsche made that one connection tighter than others I've seen on this motor?

Hose on, clamp installed, and we fired up the engine. Problem fixed! Thanks to all both here and on the Pelican forum for suggestions and especially the tip to use a heat gun on that one tough hose joint!

This is a wonderful forum. Thanks guys.

Davebrossi

Hi there! Wanted to also say thank you to everyone. You folks are great! Now that I've managed to do the tear down and rebuild, hopefully I can be of help to others.