I have a case for you
I have a 2003 c5 RS6 avan with ABT chip. I have had the car for 3,5 year without major problems, except DRC (fitted PSS9 with H-sport ARB)
Approximatly 6 months ago i got a new issue which i have not been able to solve. The symptoms of the problem are as follow:
- when the car has been parked for more than 6 hours and i start it it runs with a rough idle for approximatly 30 second then its normalize and runs perfect. The roughness of the idle seems to be getting worse the longer it sits still. It will start and run perfectly if i stop for and hour and starts it up again.
- it does the same if it is cold or warm. I have the "normal" cam tensioner rattle when starting up during cold weather, but the rough idle is there independantly
- when i start it and have rough idle it get worse if i put it in drive. It seems like putting load on the engine is causing the problem to escalate
- when i pull VAGCOM failue codes i get: misfire on cylinder 3 and random misfire. Lately one of the labda banks is comming up with failure code ( open circut). The problem is the same before and after the lamda failure. Lambda ill be fixed shortly.
- when it first started i felt the rough idle was worse when the weather was wet, but now it seems to be equally bad.
I have done the followibg to try to cure the problem:
- with misfire on cylinder 3 i suspected plug, coil or injector failure. All 3 has been changed without any change. I have also checked coil wiring and it seems ok.
- reading about all the MAF failures and the fact that i feel that accelleration is not as linear as before i changed both of them without success. I did not have high expectations for the MAF change out since it i though a failed MAF would cause misfire on several cylinders
- then i started to think about temperatur sensor and that an error in the reading or drift in sensor could cause wrong mixture during startup. Replaced it, but still the same.
- The garage has also checked that there are no vacum leaks.
- increasingly desperate i have also run cylinder compression/leak test without any findings. I also have tested the cooling water circut with pressure since i had a idea that i leak could cause water to accumulate in the cylinder and cause rough idle. Both test was ok, no leaks i cooling system and good compression.
I and my garage is a bit lost to what the cause can be. A couple of weaks ago i was visiting MTM i Germany for another reason and then i had a chance to talk to their head mechanic. He could inform me that he belived the problem was wear on the cylinder heads. More spesific wear on cam shaft opening exhost valves on cylinder 3. He claimed they had changed several cylinder heads due to the same problem. Note that he was not looking at the car when the rough idle appears,he was making the conclution based on me telling him about the problem. I find it hard to belive that so little wear can cause this and that the slight temperature increase over the 30 seconds this i going on can cause expansion enough to cure it. Also,i cannot find examples on the web about people with the same symthoms and cure after a cylinder head change out.
Any comments or suggestions to the cause of my problem is highly appriciated.
update 20.06.2012
I have attached files from when data was logged today from the VAGCOM. Data logging was started before the car started (car had been standing over night and rough idle was prenset during start up) and it run until it was warm. It was started then let it ran in Netrual until the idle was ok and then the car was driven until it was warm.
I had to ZIP the files since the site did not accept .CSV files. One of the files is the original CSV file and one is the .xls file i creasted by importing it inot Excel (easier to reasd, for me at least).
Update 09.07.2012
Short update.
Delivered the car to the shop yesterday and they put on ramp before wnding work yesterday. So this morning the car was cold and they condcuted a compression test before starting the engine. The compression test does not have clear indications of a leak. There are some variance from highest to lowest cylinder, but according to the shop this would be looked at as inside spesifications. Please find the comptest attached.
When the test was condcuted they did some interesting observations:
1. When they removed the spark plug on cylinder 3 the sparkplug bottom had a lighter color than the other sparkplugs.
2. They also went in with a camera and the top of the cylinder had a lighter color.
3. they cliamed the water level in the expansion reservoir was reduced from last time. Estimated a loss of 1 liter.
Based on this i guess i have reach point of no return.... i need to pull the engine and change head gaskets and potensially cylinder heads (checked with Germany and they where 1700 EUR/ea and i can probably add 30% to that for the price in Norway). Anyone out there with a better idea?
