Burnt smell from engine and error P0171

Patnut · 13th September 2020, 08:04

I have an mg zt 04 running lpg. I've had this strong burning smell coming from the engine for a long time noticed it since the lpg was fitted but other than that car drives fine... Untill now error code PO171 something about fuel air mixture where do I start?

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SD1too · 13th September 2020, 09:14

Hi Pat,

You've said that the burning smell occurred immediately after the LPG conversion. Is the smell only present when running on petrol, LPG or both?

P0171 indicates a lean mixture on the left hand bank (nearest the radiator).

Simon

Patnut · 13th September 2020, 09:23

Good point I will run on petrol and find out. Do you know if the code means I have a leak somewhere car seems to be driving fine otherwise.

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COLVERT · 13th September 2020, 13:37

Quote:

Originally Posted by SD1too

Hi Pat,

You've said that the burning smell occurred immediately after the LPG conversion. Is the smell only present when running on petrol, LPG or both?

P0171 indicates a lean mixture on the left hand bank (nearest the radiator).

Simon

Could that number be a left over from the problem he had a few days ago from the same left hand bank ??

His previous post said he'd fixed it.---

Patnut · 13th September 2020, 13:44

Quote:

Originally Posted by COLVERT

Could that number be a left over from the problem he had a few days ago from the same left hand bank ??

His previous post said he'd fixed it.---

P0304 code went away after I replaced the coil and then a few days later this came up.

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Patnut · 20th September 2020, 13:34

The engine light goes off after switching to petrol for a bit so I think it could be a bad batch of lpg as u filled up at a station i don't normally go to.

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xsport · 27th September 2020, 12:53

you need to run on petrol for 2 weeks to get the engine running well on petrol again.it will do this by itself if you dont have any issues with the engine itself. the trims will adjust themselves whilst on petrol as it has all info it needs from the o2 sensors. then after it has retrimmed itself then you can think about running on lpg and getting it remapped at a specialist lpg tuner. that is of course that you have a modern system fitted with its own ecu thats piggy backed on to your rover ecu. i do mine myself on my laptop as i have the software downloaded for my system. your lpg trims and mapping needs to follow the rover ecu mapping as close as possible .... you wont get it exact as it is only at best a compromise. this is why you need a tune up every so often. the o2 sensors will keep moving the trims on lpg unless you are within their adjustment bands to follow the original rover mapping thats in the rover ecu. you cant just run lpg on the same mapping as petrol. it runs but will throw P.O ml errrors. so get it tuned properly. also even when tuned you will occasionally have the odd wiff of burnt lpg from the engine if you drive it hard. you could also check that you dont have an exhaust/manifold slight leak on the downpipes. good luck !!!

Patnut · 27th September 2020, 13:15

Hi xsport I was starting to give up but alot of what you said makes sense. I haven't had it remapped for a few years so like u said this could be the prob as when I switch to petrol the error code goes away.

So I should run it on petrol for a couple of weeks then take it to be calibrated on lpg? I actually have the cable and software for my stag system so could do it myself if I knew how!

I actually thought it was because I reduced the switch over threshold from 45 to 40 a few weeks back.

Thanks for the advice will let you know how I get on.

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xsport · 29th September 2020, 00:27

its really not that difficult to tune them once you wrap your head around it. im not converse with the stag system as i use the bigas software as its quite user friendly. in my system you can adjust the offset of fuel to each bank by percentage 50/50 60/40 or whatever . which helps as it is across all rev bands. going down this line is however not advised unless the banks are way out which would probably point to an air leak on one bank only. this may not show up on petrol if only a small one and on petrol the trim corrections will be made by the various sensors already in use by the petrol ecu to adjust settings / timings etc but for petrol mainly these are the adaptations written into the rover mapping. they are for an engine designed and being run on petrol not lpg so you can see why to follow the original mapping is key to all this. however i have in the past noticed that year by year this problem of remap does tend to follow the weather temperature changes summer to winter and probably needs a bit richer in lpg to compensate. you mentioned that you lowered your change over temp recently. you would be wiser to up it to what it was before now that the weather is colder. it could well be that its throwing a p.o number before its warm enough if the mixture is a little weak and goes into closed loop on the o2 sensors. failing that do as i suggested in my last post and get a mapping done and change your inline gas filters if you have not done so already !! .....

xsport · 29th September 2020, 00:41

oh and as an after thought. dont be to critical if the banks are not equal when you look. they seldom are and you will find that they very rarely are so. just as long as they are near enough +5 to -5 you should be ok. dont know how much you are into this lpg tune on the stag system but if you have a scanner that records live data you can plug in to your diagnostic port on the car and it should give you the temp of the engine plus the rpm when the fault occurred . this should then guide you as to whether the lpg is too weak upon changeover. do whatever is best for you and good luck !! ......

13th September 2020, 08:04	#1
Patnut Avid contributor MG ZT 180+ Join Date: Jan 2013 Location: London - Wembely Posts: 140 Thanks: 16 Thanked 1 Time in 1 Post	Burnt smell from engine and error P0171 I have an mg zt 04 running lpg. I've had this strong burning smell coming from the engine for a long time noticed it since the lpg was fitted but other than that car drives fine... Untill now error code PO171 something about fuel air mixture where do I start? Sent from my Mi 9T Pro using Tapatalk

13th September 2020, 09:14	#2
SD1too Doesn't do things by halves Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model. Join Date: Mar 2007 Location: Former Middlesex Posts: 20,344 Thanks: 1,587 Thanked 3,749 Times in 3,181 Posts	Hi Pat, You've said that the burning smell occurred immediately after the LPG conversion. Is the smell only present when running on petrol, LPG or both? P0171 indicates a lean mixture on the left hand bank (nearest the radiator). Simon __________________ "Whatever is rightly done, however humble, is noble." Sir Henry Royce.

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13th September 2020, 09:23	#3
Patnut Avid contributor MG ZT 180+ Join Date: Jan 2013 Location: London - Wembely Posts: 140 Thanks: 16 Thanked 1 Time in 1 Post	Good point I will run on petrol and find out. Do you know if the code means I have a leak somewhere car seems to be driving fine otherwise. Sent from my Mi 9T Pro using Tapatalk

20th September 2020, 13:34	#6
Patnut Avid contributor MG ZT 180+ Join Date: Jan 2013 Location: London - Wembely Posts: 140 Thanks: 16 Thanked 1 Time in 1 Post	The engine light goes off after switching to petrol for a bit so I think it could be a bad batch of lpg as u filled up at a station i don't normally go to. Sent from my Mi 9T Pro using Tapatalk

27th September 2020, 12:53	#7
xsport Posted a thing or two rover 75 club se Join Date: Apr 2011 Location: Leicester Posts: 1,637 Thanks: 358 Thanked 419 Times in 310 Posts	you need to run on petrol for 2 weeks to get the engine running well on petrol again.it will do this by itself if you dont have any issues with the engine itself. the trims will adjust themselves whilst on petrol as it has all info it needs from the o2 sensors. then after it has retrimmed itself then you can think about running on lpg and getting it remapped at a specialist lpg tuner. that is of course that you have a modern system fitted with its own ecu thats piggy backed on to your rover ecu. i do mine myself on my laptop as i have the software downloaded for my system. your lpg trims and mapping needs to follow the rover ecu mapping as close as possible .... you wont get it exact as it is only at best a compromise. this is why you need a tune up every so often. the o2 sensors will keep moving the trims on lpg unless you are within their adjustment bands to follow the original rover mapping thats in the rover ecu. you cant just run lpg on the same mapping as petrol. it runs but will throw P.O ml errrors. so get it tuned properly. also even when tuned you will occasionally have the odd wiff of burnt lpg from the engine if you drive it hard. you could also check that you dont have an exhaust/manifold slight leak on the downpipes. good luck !!!

27th September 2020, 13:15	#8
Patnut Avid contributor MG ZT 180+ Join Date: Jan 2013 Location: London - Wembely Posts: 140 Thanks: 16 Thanked 1 Time in 1 Post	Hi xsport I was starting to give up but alot of what you said makes sense. I haven't had it remapped for a few years so like u said this could be the prob as when I switch to petrol the error code goes away. So I should run it on petrol for a couple of weeks then take it to be calibrated on lpg? I actually have the cable and software for my stag system so could do it myself if I knew how! I actually thought it was because I reduced the switch over threshold from 45 to 40 a few weeks back. Thanks for the advice will let you know how I get on. Sent from my Mi 9T Pro using Tapatalk

29th September 2020, 00:27	#9
xsport Posted a thing or two rover 75 club se Join Date: Apr 2011 Location: Leicester Posts: 1,637 Thanks: 358 Thanked 419 Times in 310 Posts	its really not that difficult to tune them once you wrap your head around it. im not converse with the stag system as i use the bigas software as its quite user friendly. in my system you can adjust the offset of fuel to each bank by percentage 50/50 60/40 or whatever . which helps as it is across all rev bands. going down this line is however not advised unless the banks are way out which would probably point to an air leak on one bank only. this may not show up on petrol if only a small one and on petrol the trim corrections will be made by the various sensors already in use by the petrol ecu to adjust settings / timings etc but for petrol mainly these are the adaptations written into the rover mapping. they are for an engine designed and being run on petrol not lpg so you can see why to follow the original mapping is key to all this. however i have in the past noticed that year by year this problem of remap does tend to follow the weather temperature changes summer to winter and probably needs a bit richer in lpg to compensate. you mentioned that you lowered your change over temp recently. you would be wiser to up it to what it was before now that the weather is colder. it could well be that its throwing a p.o number before its warm enough if the mixture is a little weak and goes into closed loop on the o2 sensors. failing that do as i suggested in my last post and get a mapping done and change your inline gas filters if you have not done so already !! .....

29th September 2020, 00:41	#10
xsport Posted a thing or two rover 75 club se Join Date: Apr 2011 Location: Leicester Posts: 1,637 Thanks: 358 Thanked 419 Times in 310 Posts	oh and as an after thought. dont be to critical if the banks are not equal when you look. they seldom are and you will find that they very rarely are so. just as long as they are near enough +5 to -5 you should be ok. dont know how much you are into this lpg tune on the stag system but if you have a scanner that records live data you can plug in to your diagnostic port on the car and it should give you the temp of the engine plus the rpm when the fault occurred . this should then guide you as to whether the lpg is too weak upon changeover. do whatever is best for you and good luck !! ......