So.I thought I had this issue resolved, but apparently it is sporadic, and I am not sure where to start or what to check. Any help will be appreciated...

Car is 997 TT, Tiptronic, Softronic tune, latest OEM software also B42? .... Fabspeed Maxflo, 200 cell cats. Forge BRV's.

So after initial problems, I took off headers and re-installed OEM headers as I did have a slight leak at the turbo flange on passenger side. I re-checked and tightened all connections on the Fabspeed. Dealer updated software to latest software, and I have the latest Softronic tune.

It appears when I accelerate hard for any period of time the car feels like it is missing? Sometimes it runs great....other times missing in regular or sport mode...Short high rpm bursts and runs smooth....stay on it for a bit at times and it sputters/misses. Still hauls @ss..just feel like it is skipping.

Wondering if this could be due to a sticking actuator rod on one of the VTG? If so how to test?

Also have Durametric...what can I data log and what should I look for??

I would like to get a sense of the real problem before I start paying the dealer to try to change parts like coils? etc...Plugs were changed to cooler iridium 8000 miles ago and variocam actuators changed at same time....Could plugs already be bad again? Coil packs?...

Any thoughts ideas welcomed. At a loss

Thanks,
DC

 

I have zero experience with this on my TT, but this sounds like plugs based on my experience with a similar issue on my Evo. Mis-fires due to plugs are most likely to appear at peak torque (high cylinder pressure), which would explain why long pulls are rough but short high RPM pulls are smooth. Just a shot in the dark, and I certainly wouldn't change plugs without looking at other easier/cheaper possibilities.

 

Thanks for the suggestion. It was missing bad when I first tuned it and after plug change it smoothed out. Seemed to start again after I put the new exhaust system, so maybe I loosened some hose up. or??

Hoping not the plugs again at $1000 labor!

DC

 

It is possible that your previous problems have effected the plugs. I had boost issues with aftermarket BRVs (I would not recommend them to anyone) for nearly 600 miles, which after fixed resulted in permanent issues with my plugs (only 1000 miles old).

Point is that any issues that effect fuel/air or timing can effect plugs in these cars.

P.S Couldn't hurt to try the OEM diverter valves.

 

Thanks for the suggestion. I thought about that as well..easy enough to put the old ones back on as there was nothing wrong with them..Hope it did not damage plugs.not an easy/cheap fix!

DC

 

Is your Durametric reporting any error codes (DTC's)?

 

Hi there..I did not see anything notable. I cleared it and will log the items you suggested and see what comes up if anything? I am not getting any CEL though. When I first got a tune, and the plugs were the issue...the CEL came on all the time.It has not come on once..

I will keep checking with Durametric though. Not sure exactly what to look for when I data log though?? Like what the Lambda values should be??

Thanks!

 

Well, in the absence of any error codes (and an error code will not necessarily trigger a CEL) it will be very difficult (or perhaps even impossible from a cost effective perspective) to establish a diagnosis. What I would NOT do is to start changing out various parts such as plugs, coils, sensors, brv's and whatnot with the hope that some random intervention will solve the problem. As you have pointed out, that will quickly become very expensive and your problem could remain unresolved indefinitely. Every time a change is made, a new variable is introduced and the diagnostic process has to start all over again. Personally, I would get the car to a qualified shop and spend a couple hundred bucks to have a professional attempt to identify the real problem. You can decide how you want to proceed once you have that information. If you just don't like repair shops, you can continue to drive the car and frequently check for error codes and when one or more appears, go from there. If the motor is truly "missing", the ECU should be throwing codes.

Since you asked about lambda values here are a couple of articles that help explain the mysteries of air-fuel ratios and fuel trims for your perusal. Just keep in mind that this stuff may or may not have anything to do with your current set of problems. Best,

http://en.wikipedia.org/wiki/Air%E2%80%93fuel_ratiohttp://www.obd-codes.com/faq/fuel-trims.php

 

Thanks Steamboat...Appreciate that insight and agree.....I plan on poking around a little more and if no luck, my dealer is pretty good to work with....so will likely have them take a look.

Take care,
DC

 

I am having a similar issue with my non modded 2011 TT S Cab. A PCNA tech said it could be a semi clogged fuel injector which isn't spraying the fuel correctly into the cylinder. The injectors spray at 3 different levels depending on load. No fault codes ever came up and he recommended using Techtron fuel additive to clear any debris from the injector.

 

Thanks....That is easy enough to try...and cheap. Did you try it? Have any luck?

DC

 

Yes it did help. They did a more comprehensive clean AT&T he dealership by pumping something through the fuel system. I have to pull the receipt to tell you what they did.

 

Update for anyone following this......Before I bring to the dealer, I am going to try some of the easier suggested fixes and see what I can eliminate.....

So I bought a bottle of Chevron Techtron...poured it in and ran it a bit....Do not think that did it....But it did not hurt....and always good to clean the fuel system

So next...I removed the Forge BRV - Diverter Vales...whichever name you prefer and re-installed the OEM valves (that looked in perfect shape after 25K miles or so BTW). The Driver side Forge valve looked and worked (piston moved) as it should....But the Passenger side was locked shut....Pushed on the piston with a ratchet extension and it would not budge! Locked up.....

Took it for a drive and punched it and got overboost a few times and it still sputters and hesitates both normal and sport....cold and warm ....

Odd thing is.....One time it will just scream and snap your neck and run smooth and then the next time it is very hesitant and clunky???

So....I am wondering if this may be a sticking VTG actuator rod? Maybe sometimes it sticks and other times not??? It seems odd that it runs so great at times and then other times so poor....so that made me think of the sticking actuator rod.....When I have more time I will pull it apart and see if I cannot lube them up with something silicone based and see if it helps??

I guess after that, it may be the coils or plugs?? Most expensive and last thing I will try....I have checked all the hoses and nothing visibly loose by looking and tugging at them....

If/when I get this resolved I will update for others' benefit....

DC

 

Another easy thing to check is the connector to the boost pressure sensor on the side of the Y pipe. As the cables are so tight and it probably the most used connector on the car, they can become faulty. When the car is idling if you jiggle the connector and hear changes in the idle, the connector maybe faulty. When this is faulty it results in the ECU thinking it is overboosting (in a bad way), so it vents boost (through DVs) in response.

 

Thanks Geoff...

I will test that as well. Appreciate the input. I am sure I will figure it out eventually....Just how long, and how much $$

Will keep posting updates in case it will help others...Sort of an unwilling guinea pig.

DC