limp mode but no error codes

[S2central.net]

Just for the removal of doubt... I have never ran a 3B with the carbon canister solenoid (N80 - not 'G80' as stated in Post #1) disconnected... I know the ECU will raise a fault for this, but I wonder does it also operate differently because of this....

I've just walked over to the bookshelf and picked out an Audi training book for the 3B engine and it doesn't specifically mention this scenario for N80 failure.
However it does say that if the fuse protecting N80 (and also ISV & WGFV) fails that the engine will go into limp-home mode... Most likely a result of inoperative WGFV, but it is possible at least that open circuit on N80 gets interpreted as a serious fault by the ECU.

So two things to try then - someone with a healthy 3B to disconnect N80 and observe any differences whilst 20VCQdriver simulates the presence of N80 with a resistance of 40-50 ohms. Important - This resistor needs to have a power rating of 3W to cater for 100% EVAP cycle from a factory map inside the ECU. Or alternatively - just plug in the old N80 with no pipes connected.

[20Vcqdriver]

Found the N80 valve in the garage (lucky it didn't get chucked out) so going to connect it up under the dash as cut the wiring in the engine bay for this but kept the plug. So let you know.
Weird how it cuts out to limp when the VDMS page of VAGCOM says all the sensors are spot on within the ranges allowed...
Will check all wiring too and have re instated the breather system that appears to have helped the smoke issue noticably. Now goes via a catch tank before reaching the MAF to turbo hose as oil was getting into intercooler last year via breather system...
So just got to get this limp mode sussed.

[S2central.net]

Its gonna be something stupid / unexpected / overlooked...

[20Vcqdriver]

Its gonna be something stupid / unexpected / overlooked...

Thanks, that just about covers it.. . Need time on it now, not something I'll have much of for the next 2 weeks...

[kwlw]

So two things to try then - someone with a healthy 3B to disconnect N80 and observe any differences whilst 20VCQdriver simulates the presence of N80 with a resistance of 40-50 ohms. Important - This resistor needs to have a power rating of 3W to cater for 100% EVAP cycle from a factory map inside the ECU. Or alternatively - just plug in the old N80 with no pipes connected.

I'm also running N80 connected to ECU only (no hose connections) on my AAN. Reason - when it was disconnected - ECU obviously used different idle map (rpm's changed after disconnect). Don't know how it goes on 3b.

Sau

[S2central.net]

Thats interesting kwlw... did it drive normally though with N80 disconnected or was there any problems at full throttle ?

[kwlw]

Thats interesting kwlw... did it drive normally though with N80 disconnected or was there any problems at full throttle ?

Never tried. It was way before car went out from garage to the street. But it was define change in engine noise.

Sau

[20Vcqdriver]

N80 valve wired up and was ticking away noisily behind the glovebox so quietened it down with some silicon sealant!
Re-instating the breather system as factory too with the addition of a catch tank before it enters the MAF to turbo hose. Not sure it will make much difference but have to try something.

[S2central.net]

Great... Now go drive it...

With crankcase fumes now being treated by the catch tank rather than dumping into MAF hose, I think you will have a nicer drive for sure !!!

[4WheelDrifter]

I seen to remember my 3B going into limp-home mode when the N80 was disconnected.

[S2central.net]

Ooer - that is encouraging Stu... Where is the man from the wirral then... Hopefully scaring small animals at full boost on a B-road somewhere - LOL

[20Vcqdriver]

Am still in the process of re-instating the breather system with a catch tank. Not a lot of room and trying to find somewhere for it.
For the last few months I had a hose going from the cut pipe (where the original turned into the MAF to turbo hose) running down to a large bore pipe with filter on the top. Took this apart to start fitting the proper catch tank and it was gunged up with what looked like yellow grease but only in this metal pipe and 2" of hose before it. Assume this is the effect of the oil cooling in the metal pipe and the water condensing and mixing with the small amount of oil to form this yacky concoction. I am hoping that as the tank is getting a better flow of air through it when connected back to the MAF hose that this will not happen, fingers crossed.

Anyone with a 3B care to disconnected the N80 valve and see if the car starts going into limp mode on WOT. Cheers and once again fingers crossed...

[S2central.net]

For comparison... On ABY - I unplugged my N80 - no fault code appears (I have a MIL bulb) until certain road speed or boost level was hit, but it definitely didn't trigger limp mode.

Come on ye 3B owners - want to help in the interests of science ?

[20Vcqdriver]

Well thats not fixed it. N80 and breather reinserted via catch tank. So have to wait for boost leak test next week.
Managed to stay out of limp mode long enough tonight to show a couple of chavs in a peugeot GTi what acceleration in 1st and 2nd is like with 4wd. He sat revving his engine at the lights and left tyres squealing and suddenly found this old Audi 1/2 car length ahead by the time he was out of 1st gear, despite me giving him 1/2 car length head start, into second and leaving him pretty quick now then.....limp mode cut in, but by then I'd proved the point...
Anyone list all the causes for the car going into limp mode without a code please and can then start working my way through them all.
Sure the slow spool up has something to do with it too.
On a good note, re-instating the breather system has stopped the smoking exhaust...

[4WheelDrifter]

When it goes into limp mode, if you switch the ignition off and back on does it regain power?