View Full Version : WTF is STILL going on with my car!?!
So I posted last month about the inconsistent boost, and the issue was supposed to be the MAFS. Got them replaced yesterday, and still has the issue!
I've replaced the N75, DV's, MAFS, what else could be causing this?:vhmmm:
hahnmgh63
May 1st, 2009, 21:33
Wastegates?
DHall1
May 1st, 2009, 21:38
Vag-Com and a data log is the only way to know for sure.
Is Avalon close to you? I know he will scan and do a quick log for no charge.
So I posted last month about the inconsistent boost, and the issue was supposed to be the MAFS. Got them replaced yesterday, and still has the issue!
I've replaced the N75, DV's, MAFS, what else could be causing this?:vhmmm:
Its about 90min from me, so not too bad.
vinny
May 2nd, 2009, 13:47
have you done boost leak and vacuum leak tests, p3u?
and replaced seals for MAFs in airbox and in intake tubes....??
and yes, id also definitely check wastegates....
Bigglezworth
May 2nd, 2009, 15:06
I have the same issue and going to be changing out all the rubber hoses with silicone and new clamps. If I still encounter problems after that I'll be searching just like you. Currently I'm throwing a primary and secondary air bank error so it's got to be vacuum. Not sure in your case though.
vinny
May 2nd, 2009, 18:53
hey bigglezworth, can you post those faults youre getting?
terrytcl
May 2nd, 2009, 23:50
Do you have any msifire codes?
So my car has been at the dealership for 3 days now, and they can't find anything wrong with it!:doh:
No codes what so ever.
What could cause this problem and throw no codes?!?
Just a recap, car will drive fine on some occassions, but on most it seems to lack power, guessing running close to ~300. Sometimes while in first gear it will feel slow, then come about 5500rpms its a beast again!
Shit, being beaten by a mustang gt is a joke! NOT being able to pass a Saab 9-5 accellerating 80mph to 100mph and getting maybe a car length makes me puke:
Grizz, you an expert on this beast, any clues?
DHall1
May 7th, 2009, 02:54
Buy a Vag-Com and data log the car as the problem occurs.
There in lies your problem.
Without data you have nothing.
So my car has been at the dealership for 3 days now, and they can't find anything wrong with it!:doh:
No codes what so ever.
What could cause this problem and throw no codes?!?
Just a recap, car will drive fine on some occassions, but on most it seems to lack power, guessing running close to ~300. Sometimes while in first gear it will feel slow, then come about 5500rpms its a beast again!
Shit, being beaten by a mustang gt is a joke! NOT being able to pass a Saab 9-5 accellerating 80mph to 100mph and getting maybe a car length makes me puke:
Grizz, you an expert on this beast, any clues?
Spidercat
May 7th, 2009, 02:58
Sounds like you have a boost leak somewhere. Have someone hook your car up to VAGCOM via the OBDII port and get on the accelerator until you get the same feeling. You drive and they look at their laptop.
I had a loose hose from my passenger side turbo and my car did the EXACT same thing. I heard a faint whistling sound, too, when the turbos spooled up. Sounded cool, but it was basically a souped-up 4.2 at that point. I had NO codes or CEL. Buddy mech of mine and I did above, and viola': boost leak! Potentially dangerous for turbe life since the turbo will spool higher and higher trying to meet the demand for boost (which is constantly leaking out when the pressure gets high). Took it back to the dealer, and they found the offending hose and tightened it (they had just replaced my torque converter the week before, so they had just removed the engine and probably didn't turn a screw tight enough).
Just a thought, but I'm no Grizz...:mech:
Spidercat
May 7th, 2009, 03:00
Looks like Dave and I replied simultaneously!
So yeah, what he said! Great minds and all...
hahnmgh63
May 7th, 2009, 03:07
Vacuum hoses seem to wear out early on our cars although in this case I don't think that is your problem as they would be more constant than intermittent I would think. As mentioned Vagcom is great but takes a little while to really learn it and the data logging. Low boost will usually NOT throw a code, but why it is getting the low boost can definitley be time consuming locating..hose, turbo, wastegate, electronics. The N75 was already done and that would have been my first guess as the one on my 225bhp tt was bad but didn't throw a code. Good luck and keep us posted with what you are finding our narrowing it down to.
peiserg
May 7th, 2009, 03:08
Do you actually HAVE a vagcom? my "overboost" code never showed as a CEL. I had to do a full diagnostic scan (takes 15 mins or so). Tough part will be getting your tech to spend the time to do it. They only get paid to fix things.. not really to diagnose.
Best $300 i EVER spent on this car.. including the OCT and water injection... was the VAGCOM... otherwise i'd STILL be having overboost without a code, and no dealership resolution.
ttrs6
May 7th, 2009, 04:04
p3u i have the same problem with lack of power did u ever find the problem let me no please any one thanx.:vgrumpy:
DHall1
May 7th, 2009, 04:09
We can all stand around the house on fire and piss on it. Wont get us anywhere.
Go get a Vag-Com and data log some basic tuning points.
Without data we have zip, ziltch, nada. Pissing on the house burning.
Pissing on the house burning.
What if enough of us piss on it though? :jlol:
DHall1
May 7th, 2009, 05:55
All humor aside. It really does come down to taking the time to data log the car until it acts up.
One nice thing about the VagCom is the boost table. There are two values that will log.
1. Boost called for....what the ECU is telling the N75 valve to reach.
2. Actual Boost value.....the boost value attained.
If you think about it. Just knowing these two parameters will eliminate 95% of the items that "could" cause your problem and point to the 5% of items that "are" causing your problem.
Logic and algorithms will quickly narrow down that final 5%.
Bingo.
What if enough of us piss on it though? :jlol:
Spidercat
May 7th, 2009, 06:28
Those were the same tables we used to confirm a leak. Requested boost (a lot since it was never reaching full boost because of the leak) vs Actual boost (never actually reaching the requested boost pressure because of the leak, and all the while the turbo spinning faster and faster...).
Hope yours turns out to be something simple like a leaking hose!
Anyone know of a good place to get the Vag com software? I think I'm gonna break down and get it myself, too.
DuckWingDuck
May 7th, 2009, 18:46
the vagcom software is free from the Ross Tech website, but you need to use their cable to log the data.
Anyway, here's Ross-Tech's site to download vagcom: http://www.ross-tech.com/vag-com/download/ And you can buy the cable there too.
terrytcl
May 7th, 2009, 18:49
i think you need to register it though to log...
grizz
May 7th, 2009, 19:03
Check block 115 on vagcom .
This will show the requested v actual boost. Check both your intercoolers in the lower corners .
If there are any dark oil like marks your intercoolers are shot.
I've changed 20 pairs this year ......
DuckWingDuck
May 7th, 2009, 19:24
i think you need to register it though to log...
Well, ya, the cable is what costs money, not the software. Of course, it's kind of pointless to have the software without the cable since the software is otherwise useless.
terrytcl
May 7th, 2009, 20:12
yeah, their newer cables use the dongle feature.
sorry, i was referring to anyone that buys a non ross-tech cable.
Check block 115 on vagcom .
This will show the requested v actual boost. Check both your intercoolers in the lower corners .
If there are any dark oil like marks your intercoolers are shot.
I've changed 20 pairs this year ......
Told the dealer to log it, thanks Grizz! I'll find out today or tomorrow what they get from it.
So I got the beast back, been sitting for a week now, and they could not find a single thing wrong with it! :(
I had them log the 115 block, they said the requested matches the actual...
So where do I go from here!?!:vgrumpy:
V8weight
May 8th, 2009, 23:45
Start hunting for an intermittent misfire? How old are the plugs? Have you checked the coilpacks? I'd tell you to ohm the coilpacks, but by the time you get the car to replicate the symptom, and remove the air cleaner etc, it will have cooled down, so this probably won't work. Most coil problems occur at a high temp (high resistance).
DHall1
May 8th, 2009, 23:50
You need to buy a VagCom and be ready for the next time the car acts up.
Then hook up your Vag and data log.
Till you have more data...we are all lost. :eye:
We can all stand around the house on fire and piss on it. Wont get us anywhere.
Go get a Vag-Com and data log some basic tuning points.
Without data we have zip, ziltch, nada. Pissing on the house burning.
SeattleS4
May 9th, 2009, 00:39
Failing EGT (or EGT's) can give you the intermittant lack of power problem you're describing...sometimes without throwing any codes.
*Don't ask me how I know. :cry:
hahnmgh63
May 9th, 2009, 01:11
Although if requested equals actual, and the requested is spot on, makes me wonder if it isn't the tranny or TQ?
Failing EGT (or EGT's) can give you the intermittant lack of power problem you're describing...sometimes without throwing any codes.
*Don't ask me how I know. :cry:
Sorry for my ignorance, but what are EGTs?
hahnmgh63
May 9th, 2009, 01:31
Exhaust Gas Temp sensors. There is one on each bank located just aft of the manifolds. Feed temp into the computer for corrections like the O2 sensors do for Oxygen content.
hahnmgh63
May 9th, 2009, 01:33
I had a code on my left one about 10K ago as a intermittent, I cleared it with Vagcom and it didn't come back. The are expensive, and they are real tough to get at. Audi says pull the engine but I think Grizz may have mentioned doing one or both before with the engine in the car.
I wish Grizz was in the US, then I could get the best to figure out whats wrong.
How much are they? How many hours to replace w/o removing engine?
DHall1
May 9th, 2009, 01:38
Requested=actual when the problem is NOT happening. Means nothing
Thats why Pu needs to go out and buy a Vag. Simple as that
Although if requested equals actual, and the requested is spot on, makes me wonder if it isn't the tranny or TQ?
V8weight
May 9th, 2009, 02:02
I wish Grizz was in the US, then I could get the best to figure out whats wrong.
How much are they? How many hours to replace w/o removing engine?
Let me dig into my folder of shame here and find the invoice, I just had my front o2 sensors replaced last Friday. Lets see... the sensors were $180 ea.
and $2636.80 for labor. That's 20hrs. I went to check it out while the tech had it apart, and it appeared to be about a 3 or 4 hour job. I was going to take my downpipes and remove the precats while it was apart, but after I saw what he had done to remove them, I decided I would just do it my self later on. He supported the engine from the top with a transverse bar, then removed the engine cradle, then lowered the engine/trans assy. about 3 or 4 inches, and voila, the downpipes and o2 sensors are easily accessible. The hard part appeared to be fishing the o2 sensor wires behind the engine and getting them tied back into the harness. I was having problems with my car not a wot, but at half throttle or so at moderate acceleration it would seem to cut boost momentarily then cut back in. the bad o2 sensors were creating a lean condition and it eventually threw a cel.
V8weight
May 9th, 2009, 02:05
Requested=actual when the problem is NOT happening. Means nothing
Thats why Pu needs to go out and buy a Vag. Simple as that
I agree.
snoopra
May 9th, 2009, 03:41
I seem to have a reduced boost response lately. I've noticed when I turn the motor off, the boost gauge immediately goes back to zero (no vacuum), shouldn't it go slowly? Do I have a vac hose leak?
hahnmgh63
May 9th, 2009, 05:13
No, it will go to zero very quickly.
So what does a graph of the requested and actual boost of a healthy RS6 look like?
Hy Octane
May 9th, 2009, 21:39
When you drop off your car at the dealers for them to fix this problem, do you take the tech for a drive to show them the symptoms?
Having suffered thru 3 years of mystic boost cut problems I can tell you that there are an abundance of self-protecting systems built into this motor but all do not throw codes when they fail.. It could be anything.. like the aircon temp sensor f'rinstance..
Who would think that a faulty aircon thermostat could cause a total cut in boost when the motor passes a certain temp?
Well, nobody at Audi here or in Germany was able to find this problem until the thermostat finally failed .. I got hot air thru the A/C and when they replaced the thermostat for the unit, my boost problems were solved.. Go figure..
The people responsible for designing this motor are not accessable for questioning so its a frustrating trial and error process until something fails completely and is then easier to find.
Good Luck.