4.2 V8 loss of power

A5/S5/RS5
#1

So I had my 2010 4.2 V8 RS5 delivered to me a few months back and wanted to make others aware of how I sorted out a massive issue that got so bad it was undrivable.

She was running rough and revs were all over the place…having had it just delivered I was not a happy customer. It was showing the following faults… Sport differential: System fault, Tyre pressure: System malfunction, Parking brake: malfunction, Stabilisation programme fault: See owners manual

So how did I fix this issue? The 4.2 V8 has 2 x Throttle Bodies and a connector on each…each connector having 6 x wires. I’m pretty sure that the issue was with just the right throttle body but I wanted to make sure this didn’t happen again so I sorted out both sites of wires.

So…when the V8 gets hot (or even randomly) the resistance of these wires going into the connectors changes and the engine tries to compensate.

All that was needed was 12 x wires in total (6 x wires for each connector - £112 in total!!) Remove the terminals from the connector that attaches to the throttle body, cut and solder in the replacement wires and insert into connector…Install to throttle body and repeat for second throttle body.

Cleared faults and everything has been fine ever since.

I hope that someone may find this helpful as this as I had no idea what was going on and the faults showing on the dash made me think it was a major issue.

Drive safe guys :+1:

5 Likes
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#2

That’s good feedback as these cars are very sensitive to electronic gremlins with all of the computers that run them. I am anal so every time I disconnect a sensor I spray the connectors with a Electronic cleaner/enhancer called ProGold. Audi/VW dealers sell a very good one called Stabilant 22 but it is very expensive.

#3

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161927370396334705648303154130053024×4032 2.86 MB

These are some of the wires that were removed and replaced…little blighters!

#4

Really curious to the cause of your issue, I was expecting to see corrosion on the connectors to give you the resistance change with temperature but those look clean. I’m guessing you gave the connector a good clean out (male and female sides) before you replaced the terminations?

I started my aircraft engineering life as an electrician and would see all manner of issues in connectors, usually corrosion or pushed back terminations, yours strike me as looking perfectly ok which is strange.
Glad it fixed the issue though.

#5

You are as supprised as me then! I was expecting to see some sort of oxidisation or dldeposits…but nothing my mate/mechanic found a bulletin about this as apparently its a known issue.

The original connectors have been changed out for an uprated part or so I was told

#6

If they were upgraded, it would be interesting to know when. Incorporated into production when the cars were made or just as spare parts.

#7

I think this just happened to me today

#8

Do you think brushing in some dielectric grease in the connectors would help?

#9

I don’t know much about Audi’s but it seems like a bad TB position sensor. I will run a scan tonight

#10

Not sure about how much of a help the grease would be but there is certainly no harm in trying. My mate/mechanic is finding out the part number for the replacement wires that I had installed…as soon as I get them I’ll post on here

#11

I know it is a different vehicle, but our 2009 A3 2.0T quattro had a similar failure/fault with wiring connector at the throttle body. My local Euro garage was not surprised it seems, and they ordered a set of those replacement pigtails and wired them all in. Immediate “fix”…

#12

Waiting for my mate to send me the details of the technical bulletin regarding this issue that was put out by Audi then I’ll put it all up on here

#13

IMG-20210430-WA0000
IMG-20210430-WA0000900×1600 114 KB

#14

Any info on the bulletin?

#15

Bulletin

This is NOT the bulletin I was looking for but it gives you an idea as to the issue and the repair…I will keep looking for the correct one for you and post it here once I’ve found it.

#16

Ok. Thx

#17

Since we are talking about electronics and wiring, thought i might ask as well. Recently using OBDeleven to scan my car gave the below fault codes

WhatsApp Image 2021-05-12 at 4.01.35 PM
WhatsApp Image 2021-05-12 at 4.01.35 PM740×1600 79.4 KB

At the same time, on the dashboard i have ESC Fault as an error msg. Any chance this could do with wiring or the ESC module?

Appreciate any advice!

#18

You really need Vcds to drag out the detail. Where did you end up with these errors seeing this post is almost 3 years old.