Replacing the Exhaust Gas Temp sensors on RS4

[Golich]

So has anyone done this?

My RS has started a sporadic miss at rpm over 5.5 but only after a bit of a thrash say 10mins. Dealer says that both senors are reporting sporadic faults. So they quoted me £161 each and 5 hours of labour at £63 total bill of £749!!

Ordered two from VAGPARTS at £93 each (not sure if this includes VAT) but good bit cheaper anyway! So I remeber having these replaced on my old S4 and the stealer showing me them sat on the manifold. So I figure I'm going to download the Erwin manual section and do this myself. I liike to think I'm fairly competent with all things mechanical so I'm thinking this can't be too tricky. But then there's always that "O you should have done this...." factor for the virgin.

Are there any pit falls? Do I need to set anything with VAGCOM?

I have digi camera now so I'll take loads of photos. Can't promise to put anything on here as I've got loads of photos from the various other stuff I've been up to but never got round to scanning and writting tech articles - sorry! :

[S2tuner]

I'd check and replace the MAF first if your EGT sensors show up as sporadically faulty only after a thrash. Sounds like the engine is running too lean and that one more dealer has no clue how to diagnose a MAF and how to read between the lines when several fault codes come up on their diagnostic system....

As for the replacement of the sensors themselves, it's not that bad but the heat shields for the manifolds/downpipes will be in the way IIRC... Good occasion to get rid of them BTW...


HTH,

Mihnea

[Golich]

Thanks Mihnea,

I guess I should have asked before I ordered the EGT sensors. Well I plan to the keep the car for some years so I guess I'm going to need these at some point.

If I induce this problem will disconnecting the MAF confirm the MAF as the source? Or will simply logging the MAF's output with Vagcom be enough to confirm?

[S2tuner]

A MAF log at WOT in 2nd or 3rd gear should be enough to confirm this

[Golich]

That was quick - you should be in bed at this time of night. That's where I'm off too

[S2tuner]

Lol, yeah, especially since I'm in France so it's one hour later here

Good night folks


Mihnea

[tartan_rob]

I have something similiar at 4.2k revs WOT. But I am convinced it is an airleak under load. I can't find anything though and have pressurised the system to about 1.8bar (over vacuum) and there are no leaks etc. I replaced my EGT's a year or so ago as they were faulty. The errors I get from time to time on mine are, both EGT's out of range (intermittent) or something, and Negative deviation on charge pressure...i have throttled back the boost in order to reduce the impact of the problem.

Similiar do you think?

[Golich]

Update - Well my VAGCOM was down as I'd re-formatted my hard drive and I needed my 4 wheel alignment done so I took my car along to Jim at Star Performance to see what the car was up to. Rolling road test was horrendous. 298bhp but strangely 340ftlbs with some misfiring and black smoke out the back on full load!

So we tried the MAF - ok. So looked to the output from the EGT's. one didn’t move while the other gave some dodgy reading according to VAGCOM and a consistent misfire being recorded on cylinders 4,5 and 6 while just sitting idling? I might add that driving the car both down to Jim’s and thereafter I was none the wiser. Prior to that the car was still making my 150mph bench mark over the same distance with no spluttering and felt as quick as ever?

So I took the car home and replaced both EGT's. What a pain that was. There's bugger all room. Plus there's an additional still unknown what I assume is a fully enclosed fan type motor that sits right at the back right hand side of the engine (by the expansion tank) which prevented me from removing far less installing the passenger side EGT wire. So that had to come out to get the wire routing correct. (The wiring is too short to go anywhere else.) The fan/pump is tied into the breather system but the S4 doesn't have this unit. I've taken some pics of the unit for the benefit of others. Removing this and the expansion tank to the side in my case made the job a whole lot easier.

In short all my DTC’s have gone. Car is running sweet but for this reoccurring misfire now contained to only cylinder No. 4. This is a separate problem which is barely noticeable certainly not while driving, but I’ve thought for a good number of months the idle was not quite as smooth as it should be for 6 cylinder. But you’d be hard pushed to notice it’s that minor. However, VAGCOM registers it on block 15 and it’s as regular as every couple of seconds! So I’ll be removing that plug to have a look at its condition.

All in all I’ve saved £530 on the dealer quote and learned a bit more about the beast. Money required for new shocks n springs!

Make no mistake this is no easy job for the first timer simply due to the fact that there is bugger all room to get a spanner into the passenger side EGT. Also, refitting the wiring in the same location is simply not possible without removing as yet an unidentified fan/pump unit which is easy enough but it’s a tight fit and you can’t see if there is anything attached to it and I was fearful of breaking something still attached. It turned out there was nothing, but I don’t know that at the time!

I had three different lengths of 17mm combination spanner for this job. I had to cut the EGT wire with a junior hacksaw to get one short ring ended spanner over the EGT nut. Thankfully it was still strong enough to get enough torque on it when installing the new EGT.

It would have been easier if I’d removed the oil line from the turbo and possibly the water line to gain more access. But I didn’t have any suitable containers and was determined I didn’t have to do this. It helped removing the driveshaft splash guard.