02 Boxster idle issues

[The Glademister]

My wife's '02 Boxster is experiencing some issues with idle. A couple of weeks ago she said it was having troubles backing out of the garage after a cold night. So I started coming out about 15 minutes before her leaving for work and giving it a good warm up. But I didn't notice any problems after starting up. Then last Friday it threw a code with the check engine light. The Durametric revealed this...

So I clear that code and instantly the idle goes to crap So I looked at the real time readings and nothing is really jumping out at me (low voltage on O2 sensors, MAF, etc) The only oddity is the two TPS show different readings - TPS 1 is low at idle .5 V and TPS 2 is high 4.5 V (both approx.) So I take the car for a drive to watch those readings and at 1/2 to 2/3 throttle those move toward each other which I believe is normal. And, when I get back to the house after a few minutes, the idle is mostly smoothed out (fluctuating about 250 RPM). So I called a trusted mechanic and after describing everything he's thinking vacuum leak. And because it's both banks, he thinks pre-throttle body. Cold weather here so I take great care opening up the engine compartment by warming up the car and garage (don't want to have to by a new top ). Nothing amiss in there. All readily accessible hoses tight and secure. I sprayed some ether around some of the junctions trying to affect idle but no changes.

So do these symptoms sound familiar to anyone? Are there any vacuum hoses prone to leaking in cold weather? My mechanic buddy says they've been seeing a lot of cars with leaking o-rings in cold weather.

[paulv]

Here are the areas to look at:

-- Incorrect signal from MAF sensor
– Intake air system leaking
– Fuel pressure too low
– Volume supply of fuel pump too low
– Fuel injectors fouled
– Exhaust system leaking

Do in order:
1) Check MAF
2) Check for exhaust leaks
3) Check for intake leaks
4) Check fuel pressure/volume

Since you have the Durametric check the actual values of the MAF sensor:

Ignition on, engine off: 0.9 to 1.1 volts
Engine on (at idle): approximately 1.4 volts.

Regards,
paul...

[The Glademister]

Originally Posted by paulv

Here are the areas to look at:

-- Incorrect signal from MAF sensor
– Intake air system leaking
– Fuel pressure too low
– Volume supply of fuel pump too low
– Fuel injectors fouled
– Exhaust system leaking

Do in order:
1) Check MAF
2) Check for exhaust leaks
3) Check for intake leaks
4) Check fuel pressure/volume

Since you have the Durametric check the actual values of the MAF sensor:

Ignition on, engine off: 0.9 to 1.1 volts
Engine on (at idle): approximately 1.4 volts.

Regards,
paul...

Outstanding. Thank you very much Paul

[paulv]

PM sent

Regards,
paul...

[M711]

My 02 started generating a CEL along with some error codes -- I can't recall them now -- that had me thinking MAF. I was so convinced after some weeks that I replaced the MAF. Turned out the problem was a leaking oil filler tube cap.

Another time on a cross country drive the CEL would come on and the error codes -- as above I can't recall them now -- had me thinking MAF. I decided to press on and the 3rd day after reaching my destination upon cold engine start the exhaust billowed oil smoke. Not MAF. AOS.

[The Glademister]

Originally Posted by M711

My 02 started generating a CEL along with some error codes -- I can't recall them now -- that had me thinking MAF. I was so convinced after some weeks that I replaced the MAF. Turned out the problem was a leaking oil filler tube cap.

Another time on a cross country drive the CEL would come on and the error codes -- as above I can't recall them now -- had me thinking MAF. I decided to press on and the 3rd day after reaching my destination upon cold engine start the exhaust billowed oil smoke. Not MAF. AOS.

And that's exactly what it turned out to be on Jami's car. AOS. What clued me in was the oil residue on the exterior of the intake pipes post AOS line connection. I also read Wayne's book and he mentions that. So I got a replacement AOS and a buddy and I did the job. Not pleasant at all. Those OEM clamps on the flex tube from the crank case suck We replaced the bottom clamp with a good 'ol screw type. I also cleaned the MAF and we buttoned everything back up. I put the Durametric on it and cleared the codes again. This time the idle did not go to crap. But on subsequent driving trips we've had it stall at red lights. I believe this was just the DME re-learning the idle (which is much leaner). Those stalls have gone away now and the Boxster appears to be running great