Backfire, Knock and EGT fault code LCR

[DannyC87]

In the last couple of days my LCR has backfired twice, I'm not talking about popping, I mean gunshot like backfires. It does it when not fully warm with a bit of boost, not WOT whilst accelerating but lifting off slightly to avoid wheel-spin. I have checked for error codes and ge the following:

17584 - P1176 O2 Correction Behind Catalyst,B1 Limit Attained (De-cat)
17863 - P1455 Exhaust gas temperature sensor 1 range/performance
16712 - P0328 Knock Sensor 1 Circ High Input

I have also noticed that my AFR doesn't instantly go to max (2.0) when coming off the power which I'm fairly sure it used to. Instead it hovers around 0.7-0.8 for around 1 second before going to 2.0.

Does 17863 suggest my EGT sensor is on the way out? And it the knock sensor directly related to the backfire?

Can anyone shed any light on this please?
Thanks

 

[Willie]

Danny, are you saying you don't have a post CAT Lamda due to a de CAT?

 

[DannyC87]

Danny, are you saying you don't have a post CAT Lamda due to a de CAT?

No, it is still there, it just triggers the code because it is seeing more pollutants than it should! It is spaced out from its original location using a second boss welded to the original moving the sensor further out of the gas flow.

 

[Willie]

Could be a CAT not working to true performance prior to it being up to temperature.

Less Shumacher and more Miss Daisy till she's warmed up

 

[DannyC87]

Could be a CAT not working to true performance prior to it being up to temperature.

Less Shumacher and more Miss Daisy till she's warmed up

No CAT at all. This is my thinking; I'm doing a 260mile run in the next couple of days so will get her up to temp, clear all codes and see what comes back.
Any advise on the EGT? What sort of EGT's are safe? Race diagnostics gauge shows a max of around 950*c

 

[BoomhaueR]

I believe idle exhaust temperatures are somewhere around 600-700 degrees C, and on full tilt it goes up to around 950 degrees C. But don't quote me on that!

 

[Willie]

950C is hoorin hot.
You'd expect this on a track dy running high boost on a restrictive set up (KO4 OEM exhaust manifold)

 

[DannyC87]

950C is hoorin hot.
You'd expect this on a track dy running high boost on a restrictive set up (KO4 OEM exhaust manifold)

yep, still running oem manifold and dp.. wot through 3rd n 4th soon sees high egts. Would implausible signal imply the sensor is shot? In the past I've had threshold exceeded or similar for egts but not implausible..

 

[Willie]

Aye implausible signal would imply broken wire of fecked sensor

 

[DannyC87]

egt sensors are ~£150 yes? DIY job to change?

 

[ibizacupra]

EGT sensor no workie it adds fuel... a lot
error mode it seems to have

 

[DannyC87]

EGT sensor no workie it adds fuel... a lot
error mode it seems to have

right, so EGT sensor not working leads to excess fuel which explains backfiring.. would knock sensors pick up backfiring as knock as I hear they are similar to microphones?

 

[Willie]

egt sensors are ~£150 yes? DIY job to change?

It's in the turbo/downpipe

 

[BoomhaueR]

Yeah the sensor itself is in the top of the downpipe very close to the turbo. The cable plugs in somewhere under the manifold I think. http://www.tyresmoke.net/forum/audi-a3-s3-cabrio/40036-exhaust-gast-temperature-sensor.html

Mine is faulty and will have to get it changed soon

 

[rydoo]

bit off topic but does ur car pop with the decat?

 

[DannyC87]

bit off topic but does ur car pop with the decat?

not really no. The baffles in the oem silencer dull the pops out.

 

[DannyC87]

Just been out quickly. Reset all codes, drove off boost for 5 mins, then on part boost it backfired again, but has not brought any codes back up. My egt sensor is definitely working as my race diagnostics gauge is getting a reading from it.. Will just have to wait and see what happens on a long trip I guess. Thanks all for your input.

 

[rydoo]

thanks for the reply mate,did your decat increase the noise of the oem exhaust?

thanks

 

[DPJ]

right, so EGT sensor not working leads to excess fuel which explains backfiring.. would knock sensors pick up backfiring as knock as I hear they are similar to microphones?

No, they are tuned to a specific wavelength. I would investigate this if the code comes back - as it it's showing as a permanent - not intermittent fault.

 

[DannyC87]

No, they are tuned to a specific wavelength. I would investigate this if the code comes back - as it it's showing as a permanent - not intermittent fault.

I have had the knock error before and put it down to using low octane petrol; it doesn't seem to reoccur when using 99ron. If it comes back would it be worth swapping the knock sensors over and see if the error follows the sensor? This would show up a dodgey sensor?