The amazing saga of a misfiring 2005 audi a6 quattro. Fuel supply
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First off be warned this is long post, please have patience and I'll try to keep it interesting.
Hey guys (and girls) welcome to my thread about my 2005 audi a6 quattro 3.2l that I got for a steal of a deal! This is really been what I can only describe as a seemingly never ending saga... it's been a ton of fun and even more frustration it's all been worth it. The car is one of my all time favorite luxury cars and fixing it all with my own hands is very satisfying. I am writing this thread to hope to find someone to help me diagnose what is hopefully the last major issue with this great car. First, let me tell the car's story and the saga of me repairing it. I have never owned a car that literally sat in my garage more than I drove it til now. Also I never imagined I could be patient enough to follow through and solve the issues causing a car to be in that position... however theres an exception to every rule and this is mine. This was one of my dream cars in highschool so to get a chance to get it for a traded graphics card I was ecstatic. I did not care if it didnt run, the key was stuck in the dash, the mmi was completely trashed, all I cared was the guy told me about the stuck key and no response after breaking into the car from locking the key in it... I thought immobilizer and headed over to make a deal. sure enough hooked up my laptop and jump box and had it running in 15 minutes. Drove it home. This car was not maintained much. But the engine was in okay shape. I got a donor car at a junk yard and rebuilt the inside and learned the details of the MOST bus to fix all the mmi and such. I paid 1000 bucks for an odis subscription to remove cp and it didnt work. Took it to a dealer and it didnt work. Ended up resoldering the SMD at64 rom chip in the control head and using a jbox to reprogram the amp to virgin and then odis to adapt it. Funny I as a novice learned this while the dealer couldn't figure it out. Being a computer expert this process was likely the easy part. next I moved to body. The paint was sad with pealing clear coat and the headlights were in bad bad shape. Overall the car had tons of what could only be described as silt in the engine trunk and under the carpet. This lead me to believe it might have sat in Katrina water as it came from Georgia. Anyways I had an arduous task of cleaning all of that muck out of everything. It's still existing in the plenum chamber and the entire car had gunk all over the bottom. to deal with these issues I put the car on ramps and used an engine cleaning wand and purple power to air blast the oil and gunk away. This led to the discovery of all the leaks and various other things I've yet to deal with or I'm not going to deal with. my goal is to restore this car to as close to the day it came off the show room floor, while maintaining a low budget. So far the low budget is relative but alot of progress has been made. Still a bunch of superfluous things to do and a few essentials. To deal with the paint I wrapped the car in vinyl it looks great. I polished the passenger headlight and replaced the driver. The headlights are adaptive range control self leveling adaptive cornering and I got them working perfect after a brief encounter of left dipped headlight. Mechanically it wasnt in the shape the guy described but I knew it was a mess when i got into it. about a month ago, the engine with 104k miles was beginning to run terribly and misfire horrible. It was also making a loud clicking which I thought was my tensioner broken but they ended up being fine. I had to embark on a large project and investment to fix my engine. I have about 200 hours of my time in it now. I'm a software engineer not a mechanic but have always loved cars. Here's a comprehensive list of the things I've done to get it back to fun... along with a todo list and a brief list of current issues. I've only owned it for 3 or 4 months so imagine that... Vag really needs to work on their reliability lol... done:
the cylinder 1 misfire. The engine work started because of a cylinder 4 misfire I rebuilt and cleaned injectors and believe I moved the #4 injector to #1 the car runs very good compared to the past but still has a vibration due to the misfire. I have a new injector but am loath to take the intake off yet again... so I noticed the engine is still clicking pretty loudly. I went to town with a mechanic stethoscope I heard uneaten idle and rough idle on cylinders 1 and 3 but none of them sounded perfectly smooth I heard a clicking noise from the intake manifold. I tried to figure out the clicking... first I thought it could be the lower manifold flaps but figured why would they be moving in idle... so then I tried to get my stethoscope on the injectors to see if #1 sounded different than other cylinders. I didnt notice much difference but it did sound at times like the gas flow was sputtering. I touched the fuel line and boom I hear the clicking super loud like exactly what I hear from the running engine. I follow the sound up the line, and find the high pressure fuel pump (hpfp) the clicking is coming from the fuel pump. It sounds terrible. is it possible this is causing the misfires and not the injector. If I replace the hpfp I will replace the #1 injector since I got a new one already. the motor vibration is intolerable and it really seems to me it must be caused by the misfire. In fact it seems to misfire almost non stop but still runs realatively smooth. I can only see the misfires in vcds if I step on the gas to WOT. Most the misfires occur after letting off gas from wot. When driving if I hit throttle to hard and it misfires the cel comes on and starts flashing. If I continue driving it continues misfiring like it wont even climb a hill and loses most power. If I coast or idle for a few minutes the engine settles down again and runs semi normal but for the constant vibration. if I turn the car off and restart it the engine operates normal again. I feel wrong saying normal because it should be smooth as ice yet it feels like I'm driving my 69 mustang... the engine shake carries through the car... but it accelerates and drives smoothish. I think its pre or post detonation causing the shaking but I'm not sure. Is there a way to check for this in vcds I think vcds is only logging actual no fire misfires but not sure. What it logs vs what I see in measuring blocks vs what I feel when running the car are all different. Also I should mention the broken sensor on the passenger side electric/hydraulic motor mount. The sensor still plugged in and jb welded to the mount but it surely doesn't work because there appears to be a piece of metal that goes into the mount which was snapped off. Could the motor mount be getting bad sensor info and causing the motor to resonate? right now my biggest concern is the hpfp. I am attaching a sound byte of it. Please if you think u can help, take a listen. Can someone check theirs that they know runs smooth and see if they sound similar? can anyone give advice to diagnose the misfires or faulty injectors I have these spark plugs that dont have a gap to set and have 3 things that surround the electrode. the resistance tested at 3500 ohm for these plugs average some closer to 3 some up to 4200... I read the stock plugs are 1k ohms. Due to ohms law this could be causing to little current from the coil packs. I have new OEM plugs ordered but not yet received to install. the coil packs are replaced off the donor car. The donor engine had 18k miles but I am 99%sure my coil packs are fine. what about the fuel filter could it cause this? If you made it this far and are still with me, here is the sound byte of the stethoscope to the hpfp... all comments and advice and criticisms are very much appreciated. I have all sorts of diagnostic tools if any one wants to see any data.... vcds is my goto. if anyone needs advice doing any of the jobs I mentioned I'm happy to help. I'm pretty much an expert when it comes to the interior electronics now also lol. |
It sounds like it is truly a labor of love as well as a great learning experience.
If you throw a number like $50.00 as your cost per hour you are at $10,000.00 (and growing) and 5 weeks of work. Being able to say this is where I started and this is where I am and that you have done it yourself is priceless. |
I'm speechless but two words come to mind.........OMG and Wow.
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vcds scans
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Heres my most recent vcds data. taken last night after i suspect fuel pump failure. I see my low pressure side is 5 bars, but couldn't find the high side readings... hopefully the high side wasn't 5 bars also that definitely means a bad hpfp.
without further ado here are the scans |
looking through my logs i see that the fuel rail pressure is a bit low but certainly not 5 bar.
Address 01: Engine (4F1 910 559 B) 00:32:23 Group 140: Fuel Supply System (Fuel Pressure Reduction) 46.5 % Quantity Valve closing Angle 35.00 bar Fuel Rail Pressure (spec.) 35.00 bar Fuel Rail Pressure (actual) Inactive Quantity Control Valve Status still, I thought spec was 42 bar but maybe i'm wrong. I guess I better start by replacing the injector. I still think i'm going to get a new hpfp because I've heard of these grinding themselves to bits and then you get metal flakes in your fuel system and it causes all sorts of headaches, mainly having to remove the entire fuel system and clean it all. if spec is 42 and mine is 35 it is confirming my suspicion that the hpfp is failing... the clicking is certainly loud and while the pump works on an oscillating motion, i don't think it should click like it is. I seriously replaced my tensioners because the clicking made me think one broke! |
So I replaced the G419 sensor tonight as shown in these pics... sadly it's no dice, the code remains. No signal... so even with my extensive resources I can not find the wiring or test procedures for this sensor. Without it esp and abs will not work. I've already replaced the abs controller and pump also.
I was looking at measuring blocks and managed to activate a system test however I followed the procedure of driving, stomping the brake to at least 30 bar pressure, then accelerate to 13mph and turn the wheel 90 degrees. I can not seem to complete the system test and now abs light is on along with esp. Went backwords a step I think. so any suggestions? https://cimg9.ibsrv.net/gimg/www.aud...fe6060283b.jpg https://cimg0.ibsrv.net/gimg/www.aud...0db5dc883e.jpg |
Tim, That is an impressive list of repairs. Sounds like you are becoming an Audi expert. |
Nice post and you're obviously putting a lot of effort into the car too. Your goal of restoring it to near production line condition on a low budget sounds pretty ambitious to me. Good luck though. Not sure i can add add any help in answer to your questions. One thing though - the spark plug resistance seems like a red herring to me. Your coil packs are going to be stepping up the voltage to sufficient level to create a spark which bridges the air gap at the end of the plug. Know what the resistance of air is? It's pretty high, so an extra 250 ohms of spark plug resistance isn't going to have much effect on the current which flows when the plug fires, IMHO. |
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found an TPI that seem to contain some of your faults...maybe you can figure something out..
cheers/H |
Originally Posted by Sverige
(Post 25222530)
Nice post and you're obviously putting a lot of effort into the car too. Your goal of restoring it to near production line condition on a low budget sounds pretty ambitious to me. Good luck though. Not sure i can add add any help in answer to your questions. One thing though - the spark plug resistance seems like a red herring to me. Your coil packs are going to be stepping up the voltage to sufficient level to create a spark which bridges the air gap at the end of the plug. Know what the resistance of air is? It's pretty high, so an extra 250 ohms of spark plug resistance isn't going to have much effect on the current which flows when the plug fires, IMHO. And so far a low budget has been a relative statement... I'm not even sure its 100 percent possible given any budget lol. |
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