Today as I was accelerating on 3rd gear from about 2,500 rpm, the car turned on a check-engine light at around 5,000 rpm. Otherwise everything seemed normal until then. After the CEL came on, the car is driving seemingly fine, with the exception that the boost doesn't get above 0.6 BAR anymore. It was consistently hitting 0.7 BAR before then.

This is a completely stock TT, with only an aftermarket exhaust.

I know that I need to pull the codes to really get going with the troubleshooting (which will happen on Tuesday with the mechanic), but I was hoping that you guys might be able to give some tips on things that I might want to look into in case we have trouble diagnosing the issue.

So far, my personal guess is that it may be related to the diverter valves (as far as I know they are still the original ones), but not sure if there is another spot for a potential boost leak that might be going on instead...

Thoughts?

 

BAD MAF.... or a boost hose got loose on the ICs... nothing to do with DVs...

 

Thank you very much for pointing me in a better direction. I'm a newbie to the 996TT's and trying to learn as fast as I can.

If it is a MAF, what is the recommended fix in terms of the part (i.e., should I get OEM MAF, or is there a better aftermarket solution)? I'm assuming that replacement is the only real "fix", if it is the MAF sensor...

 

Yep..probably in limp mode. New MAF is about $200 or so...good to have a spare one with you and the tool to change it...2 minute job.

 

Hi,Usually when the hose comes off the intercooler it would not idle to good if at all..Atleast when it happened to me..
Good Luck

 

0.6 Bar is normal for a base TT. I some times see .7 but only for a second. Not seeing above .6 does not indicate an issue. Check the code with a scanner and go from there. It could be anything from a missfire to bad o2 sensorm.

 

Based on suggestions here, I followed the steps in the thread:

https://www.6speedonline.com/forums/...about-diy.html

...to test the MAF output pin 5 voltage. And based on that test, I may have a bad MAF. With engine off and key in ignition I see ~1.05 V (which is ok), but with the engine warmed up and running I'm seeing ~1.65V (I understand it should be ~1.4V.) I tried cleaning the MAF sensor per suggestions in the DIY, but the voltage did not budge. So right now I'm thinking that this might be at least "a" culprit, if not "the" culprit. (I have not yet seen the codes from the system--ordered the durametric, but won't have it for a couple of days...)

 

The thing is that my car was hitting 0.7 consistently (every time I put my foot down)... until the CEL came on today, and then it would only go to 0.6. This made me fee like there was something more to this than just "stock" performance...

 

really it is best to diagnose the CEL with actual codes...until then we're all guessing...and that can be expensive.

 

Ok. I have the code P0420
Something about Catalytic Converter Efficiency - Bank 1

Can this just go away on it's own? or any advice on troubleshooting further?

 

Possible fault cause
♦ Oxygen sensor ahead of and after TWC exchanged
♦ Valve lift fault
♦ Aged oxygen sensor after TWC
♦ TWC faulty

Most likely the O sensor...either faulty or the connection is bad (try cleaning the connector, check the wires first)...reset the code and see if it comes back.

 

This is where I would start as well.

 

My info on this is if this code is accompanied by aging O2 sensor codes to replace the indicated sensors, clear the codes, and drive the car.

If the P0420 code comes back then the converter is bad.

I have not had any issues with my Turbo but my 02 Boxster generates a P0430 code every once in a while.

What I have tried and some of which helps...

First, be sure you do *not* let the plugs remain in service too long. While I let the ones in my Turbo stay in for 60K miles -- I lost track of the miles at which they were last replaced -- and no problems arose not all engines/converters are the same and you might have an engine/converter a bit more sensitive. No need to replace plugs weekly but at least change them out when they are due on if not on miles on time.

The Boxster plugs are kept reasonably fresh that is changed when they are due.

Also, what I can tell you helps is to use a bottle or two of Techron according to directions. I like to do an oil/filter service after the last tank with Techron in it is down to say 1/4 level.

No need to use Techron more than a bottle or two. Once you have used it then what follows is what keeps you from having to use it again.

Switch to and stay with a top tier gasoline. I tried discount station gasoline a few times when gas prices got sky high but the error code would appear more often. During a drop in gasoline prices I switched back to using Shell (not a recommendation just that it is a station very convenient to me and offers competitive prices compared to other top tier stations in my area) and the frequency of the code appearing dropped.

I have managed to get the car though smog checks now for several years though eventually I will have to replace the converter indicated by the error code.