New to forums. Surging problem. Help!

[DGISNOT]

Hey guys,

I bought a stock '02 A6 2.7T Tip with @65k on the clock (love it, BTW) 2 months ago and all was well for the first month. Shortly thereafter I noticed a small drop in power (as measured by my seat-o-the-pants-o-meter) and just a lack of the normal, effortless torque "kick" I was getting earlier. Also the car had sort of a lopey, big cam style roughness to the idle. The most telling issue was the surging on part throttle and WOT. Since my experience with this car is limited I just kinda thought it might be my imagination so I left it alone. A few days ago I had the windows tinted (my first "mod") and the installer left the ignition on for 2-3 hours so that he could roll the windows up and down during the tint job. When I got in it and left I noticed it was throwing a CEL so I was a bit concerned. All that went away, however, since the thing ran like a scalded ape!! The power was back up , idle was better, and no surging on acceleration. I drove it like that all day enjoying the hell out of it partly satisified that the prob was solved (except for the CEL of course) and went to bed happy. Got in it the next morning, no CEL, and back to surging, rough idle, etc. WTF, anyone heard of/had this happen and if so what was your solution? And of course any other suggestions are welcome.

FYI, I checked all the vac lines (the ones I could easily see/access, anyway) for obvious signs of problems and I don't hear any hissing noises underhood or honking turbos when driving. I guess leaving the ignition on so long performed a TBA but I have since done it 2 more times with no results.

Thanks in advance!

[DGISNOT]

bump . . .

[ryuuoh]

Throttle body boot?

[Gumby]

could be a boost leak. there are a few write ups on how to make a cheap leak tester. you can get all the stuff to do it at a hardware store. might look into it.

[DGISNOT]

I was under the impression that the TBB on '02 and newer had been corrected. Is that not the case? I'll look into a boost leak test.

Just thought it was sorta odd that I got a CEL and it ran GREATand then no CEL and things went back to normal (read: bad).

Any other suggestions? BTW: thanks for your input so far!!

[DGISNOT]

bump . . .

[Daft]

The TBB was updated but, it still can rip.

The real key is to get a peek at the CEL you had. I'm willing to get you have either a intake leak (vacuum line or even a intercooler hose) or an ignition issue (either coilpack related or just really worn plugs that are occasionally misfiring.

You will notice a large change in performance if the car is knocking alot. This will result in the ECU pulling timing and not throw any codes since the ECU is made to protect itself in these situations. The gas you use can cause knock so always use a minimum of 91 octane on these cars, never go lower as your engine will fight with it. Also, things like maintainence items (air filter, fuel filter and spark plugs) can have huge effects on the car's performance if they are not replaced at the recommended intervals. Since you recently bought this car, some of these items may be extremely old and possibly even original.

Definitely get someone to read the CEL code and you can take that into consideration on what should be looked at next. Otherwise, maintenance records can give you a good sense of what was done to the car over the last 6 years of ownership.

[04A6SLine]

get it Vag-com scan and see what's going on.. i got a scan from a local member (thank KingofNYC).. it turns out to be the temp sensors

code: P1458-35-10
p1455-35-10

i have also read that with those two sensors going bad i can loss a large amount of HP.. (sorry for jacking your thread)..

[DGISNOT]

The TBB was updated but, it still can rip.

The real key is to get a peek at the CEL you had. I'm willing to get you have either a intake leak (vacuum line or even a intercooler hose) or an ignition issue (either coilpack related or just really worn plugs that are occasionally misfiring.

You will notice a large change in performance if the car is knocking alot. This will result in the ECU pulling timing and not throw any codes since the ECU is made to protect itself in these situations. The gas you use can cause knock so always use a minimum of 91 octane on these cars, never go lower as your engine will fight with it. Also, things like maintainence items (air filter, fuel filter and spark plugs) can have huge effects on the car's performance if they are not replaced at the recommended intervals. Since you recently bought this car, some of these items may be extremely old and possibly even original.

Definitely get someone to read the CEL code and you can take that into consideration on what should be looked at next. Otherwise, maintenance records can give you a good sense of what was done to the car over the last 6 years of ownership.

Thanks, Daft, 4 the info. I have not done a "tune-up" yet so obviously I'll start there (plugs, filters, etc.). Wasn't aware these cars were so sensitive to octane. I've been using super (91 oct.) pretty regularly but did a tank of mid grade (89 oct.) when I pulled into a station that happened to be out of super. Can't really say if I noticed a diff when I downgraded the fuel (no obvious detonation) but I will keep an eye/ear on it from now on. Do you think an octane booster might help in ferreting out any issues? I'll take a harder look at the turbo plumbing as well and have the CEL code read and then keep you guys posted on the progress. Wish me luck . . .

[DGISNOT]

get it Vag-com scan and see what's going on.. i got a scan from a local member (thank KingofNYC).. it turns out to be the temp sensors

code: P1458-35-10
p1455-35-10

i have also read that with those two sensors going bad i can loss a large amount of HP.. (sorry for jacking your thread)..

No worries! I just appreciate the input and info. Thanks.

[Daft]

I've been using super (91 oct.) pretty regularly but did a tank of mid grade (89 oct.) when I pulled into a station that happened to be out of super. Can't really say if I noticed a diff when I downgraded the fuel (no obvious detonation) but I will keep an eye/ear on it from now on. Do you think an octane booster might help in ferreting out any issues?

Yeah, 89 will surely cause the car to knock much more under WOT. You won't hear it either, the knock sensors are tuned to the frequencies that knock create in the engine block and they will pick it up long before your ears will.

As for octane booster, don't do it.

Octane boosters include high amounts of MMT that will coat your combustion chamber, spark plugs, oxygen sensors and catalytic converters in a red rusty-ish soot that does not come off easily.

I discovered this when a clown at a gas station in NJ (NJ is full service only)filled my tank with 87 and I had to try and bump it back up. My plugs were gross and had started to misfire from the coating.

So always use 91 and never use octane boosters from the bottle on the store shelves. You'd actually be better off buying a gallon of toluene from Sherwin Williams and mixing it into your lower octane gas to raise the octane.

[DGISNOT]

Yeah, 89 will surely cause the car to knock much more under WOT. You won't hear it either, the knock sensors are tuned to the frequencies that knock create in the engine block and they will pick it up long before your ears will.

As for octane booster, don't do it.

Octane boosters include high amounts of MMT that will coat your combustion chamber, spark plugs, oxygen sensors and catalytic converters in a red rusty-ish soot that does not come off easily.

I discovered this when a clown at a gas station in NJ (NJ is full service only)filled my tank with 87 and I had to try and bump it back up. My plugs were gross and had started to misfire from the coating.

So always use 91 and never use octane boosters from the bottle on the store shelves. You'd actually be better off buying a gallon of toluene from Sherwin Williams and mixing it into your lower octane gas to raise the octane.

Good to know. Thanks again. I'll let you know how things progress.

FYI: lately the car has been running better (mostly) and has only been surging a little. No rhyme or reason to it, however. Turn it on and go one time and it is great and the next time back to its bad tricks. Mostly better, though.

[DGISNOT]

UPDATE: built myself a boost leak tester and low and behold found a pretty big leak at the rubber connecting pipe between the Y-pipe and the turbo (or is it the IC?) inlet; you know the one with the pigtail for the DV? It is sort of a Y shaped rubber boot as well. Sorry, I am still learning all the correct terminology for my new car's parts!

I can actually feel the air leak when I put my hand under the junction of the 2 pipes. Can't see a hole/tear so I suspect the leak is coming from underneath the clamp.

My questions are these:

1. Should I replace that rubber hose coupler or just reclamp it?
2. If I replace it, should I go OEM from the stealership or is there a better aftermarket alt?
3. The clamps seem to be "one use", similar to the hose clamps on my MV Agusta Brutale so should I go back to OEM or upgrade to aircraft-style screw clamps to help prevent this failure in the future?
4. What's the best way to get the old clamps off? Special tool (like my MV) or just snips and muscle?

Thanks, again, for everyone's help and input. I am well on my way to resolving this issue!

Darrin

[audidub0490]

it all depends on where the leak is coming from if you could just move the hose some and re clamp it go for it see if it works if not well there went your free fix and just get another part form the stealership or online... as for the clamp on both my rado and a6 the only clamps i use are rounded edge clamps so it wont cut into the rubber hoses... should be able to get them at any auto parts store if not any performance shop should have them. i have always just cut the old ones off not sure if there is a "proper" way to take them off... but none the less fix that small PITA and get her breathing right again

[Daft]

It sounds like you have a rip in one of your inlet pipe couplers.

Are you describing these hoses?




Those don't carry pressure but, they would allow un-metered air to enter the pipe and lean out the A/F mixture. The suction from the turbo's compressor will definitely be able to draw extra air into the pipe through a tear in those couplers.

[DGISNOT]

It sounds like you have a rip in one of your inlet pipe couplers.

Are you describing these hoses?




Those don't carry pressure but, they would allow un-metered air to enter the pipe and lean out the A/F mixture. The suction from the turbo's compressor will definitely be able to draw extra air into the pipe through a tear in those couplers.

Thanks, Daft, yep that's the one (on the right side or airbox side of the motor). So if those couplers don't carry boost pressure, are you saying that there is enough back pressure or vacuum in the system there as to cause unmetered air to mix in through a leak, leaning out the mixture enough to cause the hesitation I am experiencing?

FYI: Today I started the car up (mind you, this is after farting around with the boost leak tester last night) and it was running great with no hesitation. I went to my first client's office, did my thing, and left. I noticed I had that pesky CEL again and of course it was still running fantastically. The CEL went out after the next appointment in my day but still running good. I am curious to see how things look tomorrow morning!

I am going to my local German car enthusiast shop this week and have them read the codes. They are also my local APR dealer so . . .

Thanks again

Darrin

[A62TURBO]

It could be a faulty DV as well

[DGISNOT]

It could be a faulty DV as well

Thanks 4 your input. I have read on these forums that when the DVs start heading south you can hear an audible "honking" noise from them. Is that true or can they go with no noise at all. BTW: mine are quiet as a mouse!

Thanx again.

[A62TURBO]

Thanks 4 your input. I have read on these forums that when the DVs start heading south you can hear an audible "honking" noise from them. Is that true or can they go with no noise at all. BTW: mine are quiet as a mouse!

Thanx again.

You can only hear your dv's under wide open throttle, at idle they are quiet. I think my dv's are going bad right now as well.

[2.7tDallas/JonD]

Hey guys,

I bought a stock '02 A6 2.7T Tip with @65k on the clock (love it, BTW) 2 months ago and all was well for the first month. Shortly thereafter I noticed a small drop in power (as measured by my seat-o-the-pants-o-meter) and just a lack of the normal, effortless torque "kick" I was getting earlier. Also the car had sort of a lopey, big cam style roughness to the idle. The most telling issue was the surging on part throttle and WOT. Since my experience with this car is limited I just kinda thought it might be my imagination so I left it alone. A few days ago I had the windows tinted (my first "mod") and the installer left the ignition on for 2-3 hours so that he could roll the windows up and down during the tint job. When I got in it and left I noticed it was throwing a CEL so I was a bit concerned. All that went away, however, since the thing ran like a scalded ape!! The power was back up , idle was better, and no surging on acceleration. I drove it like that all day enjoying the hell out of it partly satisified that the prob was solved (except for the CEL of course) and went to bed happy. Got in it the next morning, no CEL, and back to surging, rough idle, etc. WTF, anyone heard of/had this happen and if so what was your solution? And of course any other suggestions are welcome.

FYI, I checked all the vac lines (the ones I could easily see/access, anyway) for obvious signs of problems and I don't hear any hissing noises underhood or honking turbos when driving. I guess leaving the ignition on so long performed a TBA but I have since done it 2 more times with no results.

Thanks in advance!

bad Throttle body boot or By Pass Valve are the likely culprits

google that

[DGISNOT]

You can only hear your dv's under wide open throttle, at idle they are quiet. I think my dv's are going bad right now as well.

I don't hear anything from the DVs at WOT but I did hear what sounded like a slight "honk" under hood when entering a freeway on ramp at open throttle only to let off the gas abruptly when the yayhoo in front of me slowed inexplicably. The sound occurred right after off throttle. Think there is any correlation and could that sound be the dreaded honking DV?

Oddly enough, right after that the car started to run really well! Go figure.

[DGISNOT]

bad Throttle body boot or By Pass Valve are the likely culprits

google that

Thanks for your input.

I did a boost leak test and didn't find an obvious fault in the TBB. By "bypass valve" do you mean the diverter valve(s)? That is next in my investigation.

I am going to have my CEL DTCs read by my local German car shop early next week when I can get by there.

Where in Dallas are you? I'm in Southlake.

[DGISNOT]

UPDATE:

Read my CEL codes and only got one: P0155 (Bank 2, Sensor 1 O2 sensor malfunction). I cleared the code and it has not come back.

I reclamped the intake hose connector, replaced aircleaner with a K&N drop-in, installed new 710n's and boost leak tested it again and all is well. The car is running really strong, now, with just a tiny "stutter" at WOT with no loss of power through the rev range and idle is almost perfect (just a barely noticeable roughness). Plugs are next as according to the maint log book from the previuos owner they have not been changed in @ 30k miles (or more).

As I said, though, no CELs since I have done this work. Any chance the O2 sensor code was related to items I have since replaced or is the sensor really going bad?

Any suggestions on what plugs to go with? OEM or others? Stock or other gap?

Thanks again for everyone's help. This car is really growin' on me!

[Stampy]

So much C5 love in this thread.

Only thing I can really add is that you might want to change your vacuum lines. The ones that VAG uses dry rot after a few years. I had the loping you described on my 4.2. All my lines looked good, but after I swapped them my car sounded normal. The stuff they put over the lines make it hard to spot a leak even if its really small. I just consider it preventative maintenance nowadays. Just a suggestion.

[DGISNOT]

So much C5 love in this thread.

Only thing I can really add is that you might want to change your vacuum lines. The ones that VAG uses dry rot after a few years. I had the loping you described on my 4.2. All my lines looked good, but after I swapped them my car sounded normal. The stuff they put over the lines make it hard to spot a leak even if its really small. I just consider it preventative maintenance nowadays. Just a suggestion.

Thanks Stampy. I will be taking a harder look at my vac lines. In the meantime the CEL has come back so I did some more research and it turns out that a bad/malfunctioning O2 sensor can cause all the symptoms I was having (surging, hesitating, loss of power, rough idle, etc.) Next job is to replace that pesky O2 sensor. Oddly enough, when the CEL is on, the car runs MUCH better in every way than it does after I clear the code! Go figure, right?

[livingitup]

did replacing this o2 sensor fix your probs? Im having the same code after I replaced my TBB......comes on and goes away about once a day

[DGISNOT]

Nope. Needed to be done, though. Turns out I had a small intake air leak around the upper intake connecting hose (right side) that was letting unmetered air into the intake side under high boost conditions that was causing the surging I had. It was probably throwing the MAF sensor off. Re-clamped the hose and no more surging!

I replaced both upper O2s and the CEL is no more. You might want to check your TBB clamps for tightness/seal. Do a boost leak test with a home made tester to ferret out any probs. Good luck with it!

http://www.awe-tuning.com/media/pdf/...ure_tester.pdf

[awtst3.a6]

this thread made me say.. what