Looking for help/advice.

Have a 2002 Turbo with 140k miles bought last year only mods are 200cell TechArt ‘Racing Exhaust’ and Cobb Accessport with OTS Tunes.

I’m having a few CEL lights and I’m trying to hunt down the cause.

CEL are P0171, P0174 and P0507 along with can’t get a ready status for fuel tank vent on Durametric.

I’ve replaced the O2 Seansors and new crush rings on the exhaust to turbo when changing the Exhaust.

Two weeks ago replaced the Plugs and upgraded to 997 coils and changed to SRM Billet DV’s

I’ve done a full pressure test from the turbo inlets, zip tied everything, including FPR line, three on left of Plenum. After two rounds of pressure testing, replacing both #21check valves (both Bad), fixed bad #9 Venturi tube, replaced TB O-ring, zero leaks could be heard, no air coming out of pipe going to turbo inlet pipe, so I suspect check valve #16 is okay.

Last year when this started was also having ABS/PSM problems, So I replaced the MAF with TPI brand from pelican. Well that was a bad idea, did not fix the ABS/PSM that turned out to be bad wheel speed senor harness. TPI MAF made the car run worse, so put back in the BOSCH MAF that came with the car marked 2011.

Now that leak test has been done car runs great like never before, Boost readings from Accessport from target boost to MAP reading are matching.
So getting to the point need help getting the rest of the way.

So with the P0507, cold start idles fine, but after drive into work (30min) in drive it’s at 800rpm, put it into park jumps up to 1,100 rpm. Turn the A/C off climbs again to 1,200 rpm.

When looking into EVAP problem could it be the EVAP purge valve (#14) in the engine bay. I’ve activated it in Durametric and can hear it clicking so not electrical, but I cannot move air in either direction from the long pipe coming off it, either with car on or off. Or could it be the #16 Valve stuck closed?

P0171 and 74 I have no clue about, I’ve everyting about them and everything comes up with air leak but I’m sure I don’t have anymore.

Threads researched.
https://rennlist.com/forums/996-turb...-question.html
https://www.6speedonline.com/forums/...alve-16-a.html
https://www.6speedonline.com/forums/...st-stalls.html
https://www.6speedonline.com/forums/...odes-help.html
https://www.6speedonline.com/forums/...cuum-leak.html
https://www.6speedonline.com/forums/...uum-leaks.html
https://www.6speedonline.com/forums/...ode-p0444.html
https://www.6speedonline.com/forums/...cs-inside.html
And many more.

Any suggestions or advice would be greatly appreciated.

Thanks, Jason.

 

0171 is suggestive of a vac leak. given you've seemingly chased down those ( and if you have pressure tested from the turbo's? a bad #16 would've been revealed ) my "hunch" as simple as it is? is to replace with a NEW BOSCH ( #124.00 ) maf.

and good luck.

 

Few hours after posting this ordered a new Bosch MAF from Amazon will be here Friday, I'll update with results.

 

New Bosch MAF = Same result .

As soon as car is warmed up high idle. Don't have enough drive cyles to know about the lean codes yet.

So frustrating.

 

an idle "hunt"? i.e. up/down from 750/1000? back down?

did you do the TB "reset" after to you replaced the MAF? ( you must )

I'm going back to square one. a VAC leak. a pressure test is next, if you put in a new maf AND reset the throttle body. again, GL.

 

I did do a TB Reset after do it any time I change MAPs or disconnect anything.


Its not hunting, on a cold start will stay at 750-800 in park or in gear, then after warmed up stopped in gear will stay at 750-800 put it in park will climb to 1100 and stay there, unless I turn off A/V then will go up to 1200.


In the near future I'm replacing my ICs and Boost Hoses and will do another full pressure test.


Dose anyone know if from the turbo pressure test will show leaks in the EVAP system up front of the car?

 

pressure test is the ONLY way to isolate/identify VAC leaks in these cars. faulty components are another story. however, cel codes usually point you to the few issues that could exist. absent soft or stored codes? = anyone's guess. sorry i couldn't be more helpful. gl.

 

I'm curious if you ever figured out the cause for the P0507 code. I have had the same issue on my 996 GT2. (54k miles) I've tried various attempts to find the air leak (not the smoke test yet) but no success. I've had the plenum off and cleared everything on the intake It idles normal (800'ish) on first startup but once warm I get a high idle although with the AC on it does idle fine which is the only way to check the oil level.
My wrench says it is the idle sensor and not likely an air leak. I don't sense any performance issues just the CEL and the high idle once warmed up. I do need to see what/where the idle sensor is but haven't had a chance to look at the manual yet.

 

​​​​​​Yeah mine ended up being the the vent hose from the oil tank to plenum had a big hole in it sucking in un-metered air and causing the high idle. Pressure test didn't find it becuse the check vavle in the plenum found it while the car was running and reaching around back there and felt the air sucking in. Got the hose from dealer.
The evap leak was the car connection to the evap tank under the front wheel well was not connected.

 

anytime i have had idle surging that was eliminated by having the a/c on - then would no longer fluctuate. it has always simply been a faulty maf. although those symptoms do mimic a vac leak.

 

Interesting, thanks ! That gives me a few more possibilities to check out. The MAF doesn't seem to be the problem, but could be. The vent hose to the oil tank is also possible although I checked it. Other than being a PITA, the car still runs great.