jb1856

This is one of my first posts regarding my s6 that I have been enjoying (mostly) for the last year. Searching old posts on this forum has been very helpful in diagnosing and fixing some of the annoying issues that have reared their head in my year of ownership.

That said, there is an issue that I can't seem to find a previous post or DIY that addresses exactly what I am experiencing. Basically, after installing a 034 stage 1 chip, I have been having a frustrating hiccup that has only manifested itself when driving on the highway at lowish rpms.

It happens when I am in 5th gear, between 70-80 mph, and I let off the gas to coast, and then come back on throttle (it doesn't seem to matter if my foot is leaden or soft when i come back on throttle), the car bucks or hiccups, for a split second. and then it is fine. It is a very disconcerting feeling, and I am concerned it isn't doing anything good to the engine, so I've been trying not to drive the car on the highway until this gets resolved.

here is what I have done without a noticeable effect:

New upgraded bosche diverter valve
New spark plugs
New red-top (from the v8) coil packs
New turbo to x-over pipe hose
installed s4 aluminum x-over pipe


Already installed (with no visible issues):
Samco - michelin man hose
034 Motorsports turbo to MAF hose.


The only hose I haven't yet replaced is the intake hose, and I will be doing that next weekend.

Any suggestions about how I should go about diagnosing and fixing this?

Thanks in advance. Josh

Joe100S

Sounds like the bypass valve to me. The stock bosch ones are complete cr@p.

See more here:

https://www.audiworld.com/tech/eng16.shtml

UrS4boy

Disagree. I run the 710N on my RS2'd engine and the Bosch bypass valve is just fine, especially for the money.

Note: I am NOT saying Forge DVs are crap.

UrS4boy

Josh: Contact Sam or Javad at 034 and tell them the problem and ask their advice. It is there software and there could be a bug.

Joe100S

You can test the valves really easily. If the diaphragm is ripped this could explain the issue. Seems like it's worth the 10 minutes to rule this out.

jb1856

Thanks Dave - I'll do that and report back if that ends up being the issue.

Joe - I mistyped, and I have indeed checked and switched the bypass valve to the 710N with no improvement.

Josh

8 misbehavin

Was this issue resolved and if so, what was the fix?

Joe100S

Mine turned out to be two boost leaks. Alex at IA tracked them down in short order today.

While I was there he also updated my ECU with a little upgrade (pulled my S3 and plugged in S3+), car is wicked good now. I'll be doing my motor mounts as they have started to sag. Probably do the transmission mount and the center support while I'm at it. Otherwise the car is really good and fast as hell now.

Pressurize the system from the turbo outlet and see if you've got a leak somewhere. You'll hear it if you pump about 10lbs into the system.

J

UrS4boy

When you get to the testing of your boost hoses, you might want to consider these:

jb1856

I spoke with Sam at 034, and he directed me to test to see if the ECU had some issues with the upgraded (red top from the v8) coilpacks I am running. I did a third gear pull to redline with what seemed to be full boost, and no hiccups or hesitation, so that apparently rules that out.

My next step is to look at boost leaks. Dave, your suggestion is a method to test the intake to turbo to intercooler hoses, correct?

I haven't cleaned my MAF yet, although I have cleaned the connectors. A mechanic friend of mine (who does not know audis very well) wondered if there might be something akin to an EGR valve on these cars that I could check?

If I find anything, i'll report back. thanks for all the input everyone.

Josh