Member Since: 07 Apr 2015
Location: Wanborough
Posts: 254
V8 with codes P0172 and P0175
Having problems with the V8, I have been getting the error codes above and the dreaded yellow light on the dash. I have given it a good look over (and as a bonus discovered my very minor coolant leak, been topping it up every 1000 miles or so for some time - the bleed cap gasket on the T piece had failed and it weeps), cannot see anything wrong. Cleaned the throttle body which was not too bad, but still getting the faults. I don't think I am looking for an air leak into the manifold as that would mean it ran too lean (although while cleaning the throttle body I took the opportunity to put the gasket in between the body and the inlet manifold which was completely missing!). My instinct is MAF sensor, but given it is not a £2 part I would like to try and actually diagnose that it is faulty before just chucking parts at the vehicle.
I have IID, but I am reaching the limits of my knowledge so would appreciate any advice people have to point me in the right direction as to what I should look for.
4th Dec 2018 1:20 pm
Alphamale
Member Since: 28 May 2014
Location: Belfast
Posts: 496
Try cleaning the MAF and see if it helps.
Other possibilities are, leak in vacuum system or fuel pressure problems. The last 2 are not as likely as the MAF being dirty or faulty.
4th Dec 2018 7:05 pm
Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10375
nightmare them codes.
YOu could try disconnecting the MAF, turn the ignition on for 5 seconds or more.
Plug MAF back in.
I believe this resets the fuel trim. And should last a while without producing codes, unless there is a serious problem
4th Dec 2018 7:54 pm
Mogwyth
Member Since: 03 Oct 2014
Location: Pwllheli
Posts: 3976
He has an IID he can reset them using that.
Could be worth changing the PCV valve if its blocked it can cause rich running==================================
05 D3 HSE V8 4.4
04 MG TF 135
03 MG TF 115 Cool Blue Edition
02 MG TF 160
00 Hymer B564 Lionheart
1971 Series III 109
4th Dec 2018 10:30 pm
Bungle
Member Since: 07 Apr 2015
Location: Wanborough
Posts: 254
Alphamale wrote:
Try cleaning the MAF and see if it helps.
Other possibilities are, leak in vacuum system or fuel pressure problems. The last 2 are not as likely as the MAF being dirty or faulty.
Tried cleaning the MAF (put some cleaner through it at the same time as I did the throttle body).
I would have thought a vacuum leak would have led to lean running as there would be more air getting in that was allowed (by the throttle body) or metered (by the MAF sensor).
Fuel pressure - presume this is something I can check using IID, but I don't know what the correct values are..... Sometimes I think things were much better with a pair of carbs on a 3.5!
5th Dec 2018 1:01 am
Bungle
Member Since: 07 Apr 2015
Location: Wanborough
Posts: 254
Pete K wrote:
nightmare them codes.
YOu could try disconnecting the MAF, turn the ignition on for 5 seconds or more.
Plug MAF back in.
I believe this resets the fuel trim. And should last a while without producing codes, unless there is a serious problem
Hmm, yes I can clear codes and the light stays off for a while (quite possibly long enough to get an MOT!), but that isn't going to fix the actual fault. I was hoping there was a diagnostic process I could go through to positively identify whether the MAF was faulty.
5th Dec 2018 1:03 am
Bungle
Member Since: 07 Apr 2015
Location: Wanborough
Posts: 254
Mogwyth wrote:
He has an IID he can reset them using that.
Could be worth changing the PCV valve if its blocked it can cause rich running
Hmm, hadn't considered the PCV, easy enough to check so will go for that as a simple thing to try next.
5th Dec 2018 1:10 am
aechambira
Member Since: 11 Jan 2016
Location: Nairobi
Posts: 117
Got this from Google. See if it helps. Thanks and do have a blessed day.
Thanks, seen that one. The problem is that its "truth test" for the maf sensor they suggest is contradicted on other sites which say this only works on older engines, later ones have a separate sensor for barometric air pressure rather than calculating it from MAF readings. In any case, whether it is calculated or read directly, my air pressure according to the IID tool is correct, so doesn't help here.
I think I need to make the call to either throw money at it in terms of fitting a new MAF to see if it fixes it or throw money at it in admitting I have run out of talent and bung it into a workshop. Trouble is not many of them (even LR specialists or dealers come to that) know this engine very well in the UK either!
5th Dec 2018 11:53 pm
geoffsnook
Member Since: 13 Jun 2014
Location: south wales
Posts: 3169
I was getting those codes on my supercharged could not find an air leak anywhere.But i did make sure the oil filler cap was on properly after my mate said and since then no more lights or codes Discovery 3 se gone
Range rover sport supercharged here:)
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