Calling all wrenchers/backyard mechanics

[Bigglezworth]

Did a major overhaul on my one beast here and after getting everything back together and finally back on the road hit a snag. Would appreciate input from anyone in the know more than what I understand.

You can go to my other thread (http://www.rs6.com/showthread.php/24398-Well-it-was-time?highlight=it+was+time) that confirms what maintenance work was done. Car rides super tight and like a new ride does. Love the new suspension parts. Got rid of all the error codes relating to the failing PCV system also. Engine purrs at idle and runs up to redline smoothly without any missing whatsoever. The problem however is that it is GUTLESS. As far as these cars go anyways. Car stilll accelerates fine and holds highway speed without any problems, but there is no feeling of boost. Car ran super strong and very fast priot to doing maintenance work which baffles me.

I ran the VAG-COM on it and confirmed the following:

17983 - Right engine Mount Solenoid Valve (N145) P1575 - 001 - Short to Plus
17863 - Exhaust Gas Temp Sensor 1 (G235) P1455 - 008 - Implausible Signal - Intermittent

Both codes return after being cleared.

I also through another pair of codes for each bank for fuel and MAF

17537 - Fuel Trim; Bank 2 (Mult) P1129 - 002 - System too Rich - MIL ON
17535 - Fuel Trim; Bank 1 (Mult) P1127 - 002 - System too Rich
16487 - Mass Air Flow Sensor (G70) P0103 - 001 - Signal too High - Intermittent
17482 - Mass Air Flow Sensor 2 (G246) P1074 - 001 - Signal too High - Intermittent

I'm by no means an Audi wiz like many on the Net, but from what I've learned over the years, is that bad coil packs can sometimes cause an EGT sensor error. In thinking this I was going to swap packs from one side to the other side to see if that made any difference with the code. If so, then perhaps there's a bad coil pack in there. With the car idling just fine though, and there being the other codes for MAF and Fuel Trim, I can't see this being the case

So that leads to my main question then. If there is indeed an EGT sensor that is bad, could it be causing my problem with there being no feeling of power? Engine things there is too much hot temperature in the cylinder and the retards timing and limits boost while it dumps a host of fuel in to the engine? The car is consuming fuel faster than a fat kid on a Smartie. More than half a tank on 100 miles.... Is that what the above codes are resulting from?

Again, any insight from those knowledgeable in this area would be appreciated. Also, if anyone has an exploded view diagram indicating where the EGT sensor 1 is that would be helpful.

PM or post.

Thx
Tim

[kday]

I don't have any deep knowledge of the RS6 ECU, but from what I can tell the EGT intermittent signal code doesn't hurt power, at least not dramatically -- my car has this from time to time and it's never been gutless.

Your MAF and fuel trim codes are almost certainly related -- if the MAF readings are wrong in the too-much-air direction, the ECU will inject too much fuel, leading to rich O2 readings. That is consistent with high fuel consumption too.

So for what it's worth I'd ignore the EGT for the moment and figure out the MAF issue. Presumably you had the airbox off during your maintenance -- maybe the wiring was damaged.

[4everRS]

I don't have an pic of where the EGT sensor is, but it is on the header, centered on the cylinder bank. Very hard to get to. You can access it via dripping the engine with a transverse bar. It needs to come down 6 inches or so. Did this just start happening after the other work done?, or do you think not was there before?

I would first try reseating the MAF's. I sort of doubt that is the problem and faulty egts are the main issue.

[V8weight]

What are your MAF sensor G/S readings at idle? What are your long term fuel trims right now?

[Bigglezworth]

Thanks Pat I owe some logs of measuring blocks I know. Other than the obvious 115 block, which others should I measure to confirm what you state.

I had the air cleaner assembly off yes. The harnesses both appear to be fine with wiring in tact. Normal cracking and tearing of the outer rubber sheath on both. With having two cars here, I opted to swap the MAF from the one I drove up til the end of last week with this one. Nothing changed as far as performance. No more MAF code (at least currently) but still the EGT code.

[alrightroad]

Bad MAF or intermittent MAF signal will cause terrible gas mileage. Did you clean the MAF sensors with MAF cleaner before reinstalling? Also, were your EGT's possibly expossed to elements with possibility of slight amount or rust or corrosion on sensor? The 2.7t guys have successfully cleaned EGT sensors and also resoldiered the connector at the sensor for easily repairs.

[V8weight]

I'm way out of practice, but I recall fuel trims being accessible in block 001, and MAF g/s cn be logged in blocks 002 or 003. You don't have to drive the car, just start it. At idle, the MAF g/s should be between 2 and 7. The fuel trims don't really need to be logged either, the long term will be a steady number.

[Bigglezworth]

Bad MAF or intermittent MAF signal will cause terrible gas mileage. Did you clean the MAF sensors with MAF cleaner before reinstalling? Also, were your EGT's possibly expossed to elements with possibility of slight amount or rust or corrosion on sensor? The 2.7t guys have successfully cleaned EGT sensors and also resoldiered the connector at the sensor for easily repairs.Interestingly enough the car did sit for 10-11 months without being started. I suppose its plausible that the EGT's could have rusted in that period of time, but isn't that a long shot? That noted, I see where they are both located and it looks like access from below is the only option. damn....

I cleaned both MAF with a CNC specific MAF sensor cleaner as part of the maintenance yes. I specificallly used a cleaner for MAF's vs. just a sensor cleaner. I had numerous problems prior to parking and doing maintenance, but they all pointed in the direction of a fault PCV system which was fixed and now code free. The engine maintenance was simple and straight forward which is why I'm in bewilderment on why I'm facing what I am. I will look to book a diagnostics appointment with the stealership tomorrow AM, and suspect that their first time to get me in is next week. sigh

[hahnmgh63]

At first with MAF signals too high I would say it is indicative of a tune and normal but when you are getting them along with a rich reading then I am also thinking that you may have un-metered air getting by the MAF's (not seated properly?). I would definitely go with the data logging. I think the MAF's (combined maximum) reading limit is 364.08 g/s. Under a full throttle load it should reach this logging limit, at least with a tune? The EGT sensor code is intermittent so I would worry about the rest for now, it may or may not be related to the other problems. Someone on here mentioned that a bad engine mount will cut the power? Changing the mount can be done from under the car (a lift would help) but a pain in the butt to get at the top nut and you do have to remove a few pieces under there.

[Bigglezworth]

Someone on here mentioned that a bad engine mount will cut the power? Changing the mount can be done from under the car (a lift would help) but a pain in the butt to get at the top nut and you do have to remove a few pieces under there.Found this after a host of searching and reading tonight. http://www.rs6.com/showthread.php/19684-Engine-mount-sensor-fault Mixed opinion on it leading to power loss. I'll post measurements tomorrow when I have more time. Thx. Tim

[4everRS]

When I replaced my right side motor mount and alternator solenoid, I noticed that the positive cable that goes to the alternator, makes a sharp angle around the mount. Just something to look at. If the cable wears through the insulation and contacts the mount, it will short out the mount sensor. This could also lead to alt solenoid failure. Just FYI stuff. I guess I don't buy that a mount failure causes other engine problems.

[Primo]

17537 - Fuel Trim; Bank 2 (Mult) P1129 - 002 - System too Rich - MIL ON
17535 - Fuel Trim; Bank 1 (Mult) P1127 - 002 - System too Rich

These was the error codes I got when they exchanged my HF airfilters with stock oem ones. Didn't get enough air and computer thought it was getting too much fuel.

[905084]

Bad MAF.....you said you swapped MAF...you did both, correct? Spent a month on mine wondering why no power until I used VCDS Lite and found a bad MAF. Wasted a lot of time chasing stupid s#!t like unmetered air, wiring harness, and bad I/C's.

[kevin]

The ecu is adding fuel to compensate for a lean mixture detected at the front o2 sensors. I'd start with a smoke test to locate vacuum leak(s)

Good Luck!

[ttboost]

Bad engine mount is just a nuisance. I've had one until now, when I finally replaced them both. EGT, also a nuisance. The sensor itself is located on the header right where the turbo attaches. See my pics before and after. The actually sensor module is on the firewall by the brake booster, they are bolted back to back..(1 might be red and the other might be black) I cut mine right off and had my tuner write them out. I will never buy EGT sensors again.

Bad MAF, or leaking MAF is a serious problem. The MAF determines how much air is coming in and applies the correct fueling. If it can't do this, it goes into "limp" mode. I believe that is what you are experiencing. Car will run at 3lbs of boost to protect itself. Make sure you airbox isn't leaking and your MAF's are tight, and the connectors are tightly connected. I made my own fix for this, due to Audi's idiotic airbox/MAF design, but probably shouldn't share it, as it's hack, but I haven't had MAF issues in over a year and a half...



Sorry pics too large...:cry:

[Bigglezworth]

1110Deg EGT value on passenger side vs. 365deg on drivers.... Audi states engine mount a non issue as far as limp mode so focusing on EGT sensor. Dreading the 4-6hrs swap effort. All signs suggest fixing this eliminates the limp mode.

13493

[SteveKen]

If they fit the RS6's engine harness plugs, a $40 solution (temporary or not) might be to try and use the 2.7T plugs that Adam is selling. I think they provide a constant signal to the ECU that simulates a 'normal' reading.

You should contact him to see if they work on the RS6 plugs.

Link: http://forums.quattroworld.com/classifieds-parts/msgs/28162.phtml

[Bigglezworth]

RS6 sensors monitor down to 245deg while the 2.7T sensors don't. While coding them out wouldn't be my first desire, it certainly is a solid option until such time as an engine pull is required for something else. Thx for the link.

[4everRS]

Problem with that is, if that bank of injectors doesn't function correctly, there's no correcting it, and things get waaay lean. Not good. I know this is somewhat unlikely, but isn't impossible. IMO this is worth an engine pull. And, it doesn't need to be pulled, I bet it could be done in 3 hours. You'll spend more for the EGT kit.

[Bigglezworth]

Bad MAF, or leaking MAF is a serious problem. The MAF determines how much air is coming in and applies the correct fueling. If it can't do this, it goes into "limp" mode. I believe that is what you are experiencing. Car will run at 3lbs of boost to protect itself. Make sure you airbox isn't leaking and your MAF's are tight, and the connectors are tightly connected. I made my own fix for this, due to Audi's idiotic airbox/MAF design, but probably shouldn't share it, as it's hack, but I haven't had MAF issues in over a year and a half...I swapped the MAF's from my other car over a couple of nights ago and have been running it for the past couple of days without the airbox. No MAF errors since. That said, the MAF's never seemed to sit snug inside the turbo inlet downpipes. I elected to take up a little 'slack' with a 'hack' also and now they are snug as a bug. Still in limp mode even without the MAF sensor error(s) so concentrating on the EGT item now.

Problem with that is, if that bank of injectors doesn't function correctly, there's no correcting it, and things get waaay lean. Not good. I know this is somewhat unlikely, but isn't impossible. IMO this is worth an engine pull. And, it doesn't need to be pulled, I bet it could be done in 3 hours. You'll spend more for the EGT kit.Agreed. That was why I had suggested it wasn't a permanent solution. You can do it with the engine in, but it's still a chunk of time. Uncertain it's 3hrs or more. Other posts have suggested more, but it depends on the person obviously. I have a thought of making the swapout even quicker, but not going to post it until it's tried tested and true. :)

[905084]

VCDS Lite it...

[Bigglezworth]

VCDS Lite it...I have a VAG-Com and already confirmed the bad sensor with it. Thx

[905084]

EGT? Sorry, I have ADD...

[Bigglezworth]

EGT? Sorry, I have ADD...Exhaust Gas Temerature sensor. Those nice little things that are 2-3 times the price of an O2 sensor... ha

[ttboost]

Exhaust Gas Temerature sensor. Those nice little things that are 2-3 times the price of an O2 sensor... ha

Exactly, which is why I opted to delete them..they are not critical, as there are many other engine features to help protect the engine, but they are desirable for sure. But at around $300 each, and having 2 that can go bad, forget it.

I can always put in an aftermarket sensor Maybe even in the same bung hole)...it won't work with the ECU, but can always watch it like a boost gauge...