B5 S4 top end limited to 120mph in 6th gear!

[ronaldmacdonald]

As it says, cant get more than 4800rpm in 6th gear. Got the following DTC's:

17746 - Camshaft Position Sensor (G40) Open or Short to Plus
P1338 - 35-10 - - - Intermittent

and also

17963 - Maximum Boost Pressue Exceeded
P1555 - 35-10 - Intermittent

I have recently changed the N75 solenoid valve, MAF, Spider Hose, 710n's and a fair amount of the intake hoses.

Any ideas, the dtc's i can live with but 4800rpm and 120mph?

[dummi]

cam position sensor shorting may be telling the ecu to limit engine speed? check its connection then maybe you need a new one... might bee worth checking all hoses that were disconnected and came loose and see what you find..

[ronaldmacdonald]

cam position sensor shorting may be telling the ecu to limit engine speed? check its connection then maybe you need a new one... might bee worth checking all hoses that were disconnected and came loose and see what you find..

yeah, i can check the sensor i guess with a multimeter - is it a pita to get too though, not one of these remove half the engine jobs lol!

[S2tuner]

I think it's the sensor causing your problem, damn DTC's don't bother you but you want to know what's wrong? Start fixing the problems that cause the DTCs IMHO and it'll all be better...

[ronaldmacdonald]

I think it's the sensor causing your problem, damn DTC's don't bother you but you want to know what's wrong? Start fixing the problems that cause the DTCs IMHO and it'll all be better...

Its not that I am not bothered about DTC's, I couldnt relate these two DTC's to this particular symptom, all hoses are intact and firm so I am interested in dummi's theory about the relationship between the cam position sensor and speed restriction.

[JonnyX]

Is it only 6th gear that you can't get past 4800 rpm?

How is performance generally?

[ronaldmacdonald]

Is it only 6th gear that you can't get past 4800 rpm?

How is performance generally?

yeah, just 6th gear - wot in all the other gears is fine around the rev band - I would be inclined to think this is a speed restriction rather than rev restriction, may get the chance to go out and check in 5th gear to see if I can bend past 120mph. I dont know whether the speed sensor has anything to play in this?

[s4woody]

and make sure you do it on a private rd...

[dummi]

i'd go with what Mihnea says he genuinely knows his stuff he does this every day with good results

fyi cam position sensor is on front or back of the heads, i forget which i think it is sensor front left head and rear right head, then cam position adjuster back left head and front right head, you'll see them when you open the bonnet nothing obscures them they're easy to check..

[ronaldmacdonald]

pulled the coolant tank and a few hoses out the way and realised i was looking at the wrong sensor <insert swearing etc>. found the other one on the front driver side - didn't have time for a full scale disassembly but looks like bumper may need to come off if the sensor needs replacing.

[dummi]

a6 must have more space than the s4 in the engine bay sorry!

[ronaldmacdonald]

got a quick look at lunchtime, bumper doesnt have to come off but the drivers side dv needs unclipping to make access easier - put the multimeter across it, bentley reckons 9v but i got 5v!

[ronaldmacdonald]

fascinating, i had to go on an extended sheep roundup on the private farm track we own and full power has been restored - need to check the vag-com codes. Now either this means that intermittent truly does mean intermittent or i suspect that either the connection to the sensor was crap and plugging/unplugging/cleaning has resurrected it or more likely the wiring is a bit flakey - still, will have to monitor this. Got to go, more sheep to roundup

[Morpheous]

You could check MVB for actuation of cam position, this is taken from the sensors. If one different to other nice and easy test.
I would also look whats happening to the EGT sensors. On full chat, they start climbing after 5/10 secs of full boost, make sure they are similar readings.
This is a good indicator for bank specific problems.
Long time since I looked but MVB around 90's for cam sens. cant rem without looking for EGT, think I did a post couple of years ago on it.
Also check actual and specified boost around MVB 115.
Have you checked the TBB for splits under the clip?

[S2tuner]

@Morpheous again: what do you think then of cars that show 0 and 0 in the cam position blocks before an Audi cambelt job and after it come out with -6 and +8 degrees in the same MVB? And especially of those dealerships that claim they have done the job right and that they won't take anything apart just to prove you wrong???

EGTs? What if the EGTs don't climb past 945 degrees on an S4/RS4 (the sensors don't measure below 945 degrees C), in case it has been programmed to run richer than 14.7:1 at WOT, which is how Audi runs these engines?

Lol.