MOT failure fun

MGTF failed MOT this morning - damn it.



Horn not working - button on dashboard fitted by previous owner - was working right up until MOT, now dead!!!!

Position light - bulb - easy.

Headlight insecure - forgot to put a bracket back on when doing rustproofing - easy.

Tyres - Stupid fail - put wheels back on the wrong way round after having off - left tyre is on the right and right tyre is on the lefft side - easy.

Sub frame - A bolt holding the bracket to the car has sheared off - will need to be drilled out and I assume helicoiled - never done that before, not sure how hard it is to put a new thread in.

Rear brakes - handbrake crap and breaak readings fluctuating wildly on test!!!! Hope a strip down will cure.

Emissions - C02 far too high to test - anybody know what would cause that? High c02 will be overfueling somehow. Mil light now on. Cat and one o2 sensor (does not say which one) replaaced a couple of yeaars ago according to history.

Iain.

TwistedPuppet wrote:

MGTF failed MOT this morning - damn it.




Emissions - C02 far too high to test - anybody know what would cause that? High c02 will be overfueling somehow. Mil light now on. Cat and one o2 sensor (does not say which one) replaaced a couple of yeaars ago according to history.

Iain.

Either o2 sensor or cat is scrap. Was an oem cat fitted or a cheap version. The cheap ones contain very little reactive metal and need to be very hot to work.

Do you have an obd2 reader, that'll show if it is one of the o2 sensors?

Found a guide here for helicoiling a subframe bolt and ordered a kit .

new cat and o2 sensor where fitted by a garage in 2017 and 20,000 miles ago according to the history. Cat was £100 and sensor was £80 so probably not the best.

I have a cheap scanner basic scanner that gives the p0170 fuel trim bank 1 fault but nothing else.

Did a freeze frame reaading for when the mil light came on and got :-

Fuel.sys1 OL_fault
Load _PCT(%) - 5.5
ETC(%) - 98
SHORT FT1 - 0.0
LONG FT1 - -3.1
MAP - 64
RPM - 933
VSS - 5

Also Emmisions test data from MOT, don't think anything is useful as test was stopped.



Had some weird readings not long ago might be connected https://www.the-t-bar.com/forum/9-mgf-tf-pitstop/97693-check-engine-light-weird-readings

I replaced the spark plugs, air filter etc. about 6-8 weeks ago. Car is SORN so no milage.

Old spark plugs.


They seem fine to me. Not too black and sooty and not oily.

I don't think it is actually running that rich.

I think the MOT tester told me it was about 8% O2 out off the pipe.

Do you have all the emisions readings?

O2 is about 8% in the atmosphere so I guess either there is a leak in your exhaust drawing air in or the sensor is in free air.

Sorry, I ment co not o2. I have no emisions data at all as they stopped the test "Emisions not tested (Co far too high)"

Going to need a better scanner.

My thoughts are, not going into closed loop = bad upstream o2 sensor or maybe exhaust manifold leak.
From the freeze frame data, I gather it is stuck in cold warm-up (like having the choke pulled out). Coolant temp sensor seems fine if reading 98. However all I know is what I have learnt from watching youtube videos on o2 sensors and open loop/closed loop in the last few days.

I don't get the Single p0170 code without the either of other two codes that say lean or rich. It's saying i am adjusting the fuel too much but I'm not telling you if it's too much or too little because I'm a Ars***le.

Thought the plugs would be worse as well.

talkingcars wrote:

Do you have all the emisions readings?

O2 is about 8% in the atmosphere so I guess either there is a leak in your exhaust drawing air in or the sensor is in free air.

:nonod: O2 is 21% in the atmosphere, James

Ordered a Pscan scanner today.

When it gets here, what do you reccomenf scaning for in live data?

RPM, engine temp, upstream and downstream O2 volts? Don't know all you can do with this scanner.

Iain.

David Aiketgate wrote:

talkingcars wrote:

....O2 is about 8% in the atmosphere.......

:nonod: O2 is 21% in the atmosphere, James

Depends how high you are............. https://milehightraining.com/altitude-to-oxygen-chart/

Good luck getting a MG to an altitude with 8% oxygen!

Hi,

Pscan unit arrived today and have done a quick live data scan. Been trying to turn data into line charts without success so figures only.

I was hoping it would be the upstream O2 sensor as that would be a quick fix but it seems not to be the case.

I started the feed with a cold start until temp guage was at normal - idle only.


Upstream sensor started at 0.63v and fluctuated between 0.2v and 0.75v straight away.

Downsteam sensor started at 0.47v and stayed at that for some time then started changing at 67c engine temp. Fluctuated between 0.11v to 0.9v.

Fuelling correction - not sure what this is, meant to use fuel trims but it started at 100% and moved from 85% to 110%.

Reported being in closed loop for entire test.

Any suggestions on what to test next? Engine coolant temp sensor seems ok, MAP sensor?

Iain.

Hi,

Thanks for any replies so far.

To sum up so far on emmisions fail,

Car failed MOT on too high CO to test, I think the tester said 8% and has a check engine light with a P0170 code (Fuel trim bank 1 error).

Using Pscan live data i have these reading so far.

Idle speed from cold. Reporting Closed Loop State.
Think it sounds a bit rougher at idle, can smell quite strong petrol in exhaust, idle seems steady at about 950rpm.

Over about 10mins

Manifold pressure = 52Kpa rising slowly to 57Kpa and then failing slowly to 41Kpa
Injector Pulsewidth = The same on each one and ranging from 5.461ms and over time trending down to 3.216ms
Upstreram O2 sensor = Fluctuating between 0.2v and 0.775v
Downstream O2 sensor = 0.47v until engine temp hit 67c then fluctuating between 0.11v to 0.9v
Cylinder misfire count = 1 for Cylinder 1, 0 for Cylinder 2 and ? for cylinders 3 and 4.
Fueling Correction = 85% to 110%

I cannot find freeze frame data for time of engine fault light in Pscan, cheap scanner reported a Fuel.SYS1.OL_FAULT.

Iain.