Micro Vapor Leak P0442 2001 3.4 Carrera 110k Miles

[01slvr996]

Hey all,

 

I'm having a weird issue with my car, hoping someone can lend some advice to the fuel/evap system.

 

3 weeks ago i was sitting at a light on my way home from work and my CEL came on. I got home, ran the duramatric on it, and it came back as P0442. I figured I was a bone head and cleared the code and tightened the gas cap. About 250 miles later the exact same thing happened, sitting at a light and boom the CEL came back. My buddy has a Cayman, so we swapped gas cap's and I cleared the code hoping I could narrow the problem. Here I am 25 miles later, and the light has yet again returned when; low and behold I was sitting at a light. Where do I begin with this one? Is it strange the light only comes on when I'm in stop and go city traffic? Can the duramaertic test vacuum lines or the canister purge? I did a little research and it seems like this error code can be a handful of things, anyway I can avoid a smoke test or several hundred in parts by just replacing the whole system?

[JFP in PA]

Hey all,

 

I'm having a weird issue with my car, hoping someone can lend some advice to the fuel/evap system.

 

3 weeks ago i was sitting at a light on my way home from work and my CEL came on. I got home, ran the duramatric on it, and it came back as P0442. I figured I was a bone head and cleared the code and tightened the gas cap. About 250 miles later the exact same thing happened, sitting at a light and boom the CEL came back. My buddy has a Cayman, so we swapped gas cap's and I cleared the code hoping I could narrow the problem. Here I am 25 miles later, and the light has yet again returned when; low and behold I was sitting at a light. Where do I begin with this one? Is it strange the light only comes on when I'm in stop and go city traffic? Can the duramaertic test vacuum lines or the canister purge? I did a little research and it seems like this error code can be a handful of things, anyway I can avoid a smoke test or several hundred in parts by just replacing the whole system?

 

Gas cap issues rarely throw this code, it is more often a small leak somewhere is the fuel tank ventilation system (EVAP system, EVAP purge system, shut off valve, EVAP system lines, etc.).

[01slvr996]

Any tips for trouble shooting with a durametric?

[JFP in PA]

Any tips for trouble shooting with a durametric?

 

You are not going to be able address this issue with the Durametric system, you are going to need to be looking at the EVAP system flex lines for cracks or breaks, and removing and testing the components for their integrity under vacuum.  Good old fashion hands on diagnostics for this one.

[01slvr996]

Oh boy.....  Jeff any useful insight as to what hoses to start with? I assume with the passenger wheel liner off I need to pull the evap canister and check all of those? Any other hoses I should be aware of? Any in the engine i should check?

[fpb111]

There are three valves that control the evap system. One vent valve on the charcoal can, one on the fuel filler and one above the alternator in the engine compartment. Under certain conditions the evap system is tested for leaks. Something like, fuel between 1/4 to 3/4 full, engine at operating temp,etc... The two vent valves are closed and the engine mounted purge valve is opened to build vacuum in the system. Purge valve closed monitor vacuum. If leak detected throw a code.

I would check the valves first as they are moving parts that wear. Of those the purge valve on the engine is the most active. Also If you do a search for 996 vent valve you will see a tutorial on the fuel filler mounted vent. That seems to be the one most folks change first.

"Porsche 996 fuel vent valve" on Pelican parts tech articles. Good luck, don't forget to tell us what fixed it for you.

Edited August 19, 2015 by fpb111

[JFP in PA]

That would be a good starting point, but I would also look at all the flex lines as we often find small cracks in them as well.

[01slvr996]

All great info. Jeff, are you talking about the flex lines on the canister? 

[JFP in PA]

Yes, plus others scattered around the system.

[01slvr996]

"scattered" sounds terrifying is there a diagram or something i should be cross referencing as I begin tearing my car apart?

[JFP in PA]

"scattered" sounds terrifying is there a diagram or something i should be cross referencing as I begin tearing my car apart?

 

This is one for the Boxster, but the basic components are pretty much the same:

 

[fpb111]

Smoke test should be able to expose compromised lines much quicker than visual inspection of each line. 

[JFP in PA]

Smoke test should be able to expose compromised lines much quicker than visual inspection of each line. 

 

Correct, but most DIY'ers really cannot justify the nearly $1K price for a smoke generator, which leaves them the "hands on" approach.

[01slvr996]

Hey all,

 

Just wanted to follow up, I have a question only a porsche master can answer (JFF looking at you) I got a vacuum tester from autozone and started checking lines and valves for how they would hold pressure/if i hear any air leaking. Almost immediately I noticed that the the air purge vent valve, (P/N 0280142380 the little can thing in the engine compartment that connects to the throttle body) won't hold solid pressure, it loses air, roughly 1psi every 45 seconds I want to make sure of 2 things.

 

1. Is the flow of air front to back? IE I should be pressurizing this thing with airflow going into the throttle body?

 

2. With the car off, should this valve hold pressure? any help or insight would be great.

[Ahsai]

While waiting for the Porsche masters, I can try to answer :)

1) yes and you should apply vacuum to the valve on the side that connects to the throttle body

2) yes, when engine is not running, that valve has no power to it and it should hold pressure and remain closed

[01slvr996]

Wonderful!

 

Ahsai, the pump type that I have can only pressurize going "out" if that makes sense. So if i put it on the end the connects to the TB it can only "blow" air back towards the evap, and test that pressure. Is that the correct way to test?

[Ahsai]

Unfortunately to be conclusive, you need a vacuum hand pump to simulate the natural pressure applied to the valve (vacuum from the throttle in this case). Also, you may risk damaging the valve if too much positive pressure is applied as vacuum is at most ~14.5PSI. The other thing is sometimes a leak can occur under vacuum but not under pressure or vice versa.

Edited September 27, 2015 by Ahsai

[01slvr996]

Thats exactly the kind of pump that i have, a vacuum hand pump and I've tested with max PSI of 15. But isn't it only testing vacuum under out load? IE its a "pushing" vacuum test, not a sucking one.

 

My hand pump was hooked up going to the end that connects to the plastic line that comes from the evap. I filled with 15 PSI and watched as it dropped as i held it.

 

Ahsai, are you saying i need to pressurize from the other side of the valve? From the valve that hooks into the TB?

[Ahsai]

I see. I think that should work as the pressure differential on the valve is the same as if you apply vacuum on the throttle body side.

[01slvr996]

Ahsai, is it a safe to conclude i should spend the 250 and special order this part? Anyone else have anything to chime in?

[Ahsai]

Since the part is not cheap, I would hate to see you replace a good part due to mis-diagnosis. Can you borrow a vacuum pump (from Autozone or O-reilly??) to test it the normal/proper way so you don't have to second guess the diagnosis? Of course you will have to test the vacuum pump itself to make sure it's accurate and don't give you false reading.

[01slvr996]

Good call, I'll go grab one this week and report back.