w6grace

I accidentally posted this in the 996 forum. I received good feedback but wanted to get input from fellow Boxster owners.

I have a 1999 base with an slightly erratic and high idle. Idle RPM is around 800, with occasional moments of 700 or 1000. It seems to "switch" between the 3 RPMs every 2-3 seconds. I guess I would say it is hunting.

I took the TB apart and it was very dirty, with black trails of carbon, little bit of oil. I cleaned the TB, and the ISV. It made the car perform a little better but little/no effect at idle.

The only other defect I know of is a small oil leak coming from the oil filler where it enters the engine. I am assuming I have a slight vac leak at the filler that is leaning out the motor and not allowing it to get town to idle. I also expect the excess airflow through the AOS is ringing a little oil into the TB. I don’t have white smoke when running so I dont think the AOS is busted.

. I did the "spray carb cleaner/starter fluid around the vacuum tubes and listen for any change" trick to no avail, though I didn’t get under the car to test around where the oil is coming out (its only one or two drips a day). I am planning on temporarily covering the oil leak with electrical tape to see if this solves the issue, if not I am looking for recommendations as far as troubleshooting.

Macster

Reads like the early stages of AOS failure. My 02 did the same hunting idle thing, had the same oily TB sign, when what proved to be the original AOS was going out.

The impossible to remove oil filler tube cap -- due to extreme low pressure in the crankcase -- and the smoking exhaust came only later in the end stages of the failure.

Shortly after those symptoms -- I'm told -- comes the very likely possibility the engine will experience hydraulic lock from the engine ingesting, make that sucking, its oil from its own crankcase.

w6grace

Upon further inspection I have noticed the oil filler pipe (middle one) connection to the lower pipe is leaking and maybe has a vacuum leak. I have removed the metal clamp but cant get the pipe off... Is there a trick?

I took off the J pipe and blocked both ends, this resulted in no change in the RPM issue... I have ordered a new AOS but maybe that is not the culprit?

Macster

There have been a few reports of the oil filler tube cracking/splitting and causing an intake leak.

Before you replace the AOS you need to be sure the problem isn't just the tube leaking.

I am not aware of any trick to remove this, or its clamps, etc. But that doesn't mean there are none. With my Boxster the tube has not been a problem. But my car has gone through 2 AOS's.

w6grace

2 AOS, wow that is no fun. I removed the clamp and it feels like the pipe is shrunk onto the plastic tube that enters the engine. I may try to get some WD 40 in there and see if I can shift it. I put a smoke machine down the filler and it instantly started pouring out just past the bulkhead (exactly where there is a nice oily mess all over my engine compartment. If I cant get it off easily I am going to try to temporarily block the leak with electrical tape to see if it resolves the hunting idle.

w6grace

As a side-note I noticed my power steering unit is significantly the noisiest unit at idle. Is this normal for boxsters of this era? Its hard to diagnose anything with that thing whining away at the top of the motor. Could a bad power steering pump cause the engine to run at a slightly higher RPM?

Macster

These cars do not appear to have any noisier power steering pumps than other cars. 'course the thing is right behind your right ear, albeit between a bulkhead panel that is covered with sound deadening material.

If the pump is making more than normal amount of noise that's not a good sign.

My info is a power steering pressure relief valve can fail and route too high pressure fluid to the rack. This can force fluid out past the rack seals. The dust boots on the ends of the rack catch this fluid so initially there is no leak sign.

The power steering fluid level drops. The power steering pump gets noisy. Running with low fluid damages the pump. Often the first clue the owner has there is a problem is pump noise. But by this time it is (probably) too late.

My best advice is to check the pump fluid level and if low add fresh power steering fluid (Pentosin IIRC) to bring the level up to where it should be. Do not overfill!

If the pump quiets down you may have dodged a bullet. Check the rack dust boots for fluid. Give them a squeeze. If they feel like breast implants…quit your grinning and start your spinning, wrenches that is.

The repair for this valve failure is expensive. New pump. New line with the failed valve. New rack.

If the pump fluid level is not low I do not what to say. If the pump is overly loud I'm not sure what that means. Power steering pumps have proved to be quite robust provided of course this valve doesn't fail.

Besides a few succumbing to this valve failure the next most common failure mode involves tracking. The pump overheats during tracking.

A fluid cooler seems to be the best solution. (I'm not a fan of fitting an under drive pulley to the crankshaft as this slows the rotation of the water pump, which seems simply the wrong way to go when tracking a car.)

As for the pump having anything to do with the engine's elevated idle speed, while I do not think the engine idle is elevated because of the pump I can't say for sure it is not due to this.

But more likely the RPMs are high because of an air leak.

w6grace

Ok, so I checked fluid level and its exactly where it should be, so I will assume for now that PS is fine.

I removed both clamps from the middle oil filler hose... but it wont come off from either end. I am guessing it has shrunk on.... Is there a trick to getting this hose off or should I cut it?

w6grace

Ok, so I checked fluid level and its exactly where it should be, so I will assume for now that PS is fine.

I removed both clamps from the middle oil filler hose... but it wont come off from either end. I am guessing it has shrunk on.... Is there a trick to getting this hose off or should I cut it?

w6grace

Ok, so I changed out the oil filler hose (middle one)... What a PITA it was to get out. I ended up hacking it to bits as it didn’t want to come out even after the clamps were removed. The new pipe went in really easy. The car seems to be running a little smoother....

Now I have a new discovery. There is a slight hissing sound coming from my oil filler. I also noticed there was a vacuum leak at the J tube to the AOS. I sprayed in some starting fluid and no RPM change. Is it possible that the air is flowing towards my AOS from here? Is that normal at idle?

I can still remove the oil filler at idle so I don’t think the AOS has failed... but what should I check next?

There is always a small oil leak for about an hour after I drive (usually about 5-7 drips on the RH side of the engine somewhere...