Any help please? Hesitating/backfire over 4000rpm

TamarHolley · 19th January 2015, 20:12

Hi!
I've put something about this under 'technical' but no response, so trying again here. (attention seeking behaviour, I know!)
Moonshine had a replacement front end electrical kit, with new lpg ecu, etc. All worked great! Ran the diagnostic software, and she was working well.
Except that when I drove home from workshop, the hesitates and backfires over 4000rpm. On lpg and petrol.
We had a minor issue with one lambda, so disconnected it, hoping that would be the culprit. But it's not, as she still has same issue.
So we're scratching our heads!
Levels are fine. No leaks of fuel or exhaust. Compression normal. Timing normal. Plugs all fine, as are leads. Running temperature normal. sub4000rpm, works perfectly on petrol, changing over smoothly and normally to lpg. Smooth running on both fuels until hit that level.
So, we're really hoping someone can shed light on what this might be?!
Please!!

Greeners · 19th January 2015, 20:40

get the vis motors checked

TamarHolley · 19th January 2015, 20:44

OK. Will get back to you on that!
But would that cause hesitate, misfire, and car go into limp mode?
Worth checking anyway though. Thanks.

Anon3 · 19th January 2015, 21:05

Odd at that sort of revs, but yes, power Vis came to mind for me too.

Anon3 · 19th January 2015, 21:09

For clarity, has this only come on since the LPG fitment?

You really need to seperate LPG from petrol, to sort this, at first thought.

Jordan Apex · 19th January 2015, 21:12

Quote:

Originally Posted by Anon3

For clarity, has this only come on since the LPG fitment?

You really need to seperate LPG from petrol, to sort this, at first thought.

The car was fitted with lpg before they purchased it, always been a problematic car

Anon3 · 19th January 2015, 21:18

Hesitance at these sort of revs is invariably weak mixture in my experience.

I'd suspect poor software at first glance, but don't know the background.

My first reaction would be to richen the mixture and see if it helps.
If that doesn't help, I don't have a clue, I'm afraid.

Anon3 · 19th January 2015, 21:23

Ooh, sorry, Vis motor first

TamarHolley · 19th January 2015, 21:31

I've run her since I bought her in July, and she worked perfectly in lpg until November. Wasn't aware of her former lpg issues, so would be interested to hear about them!
I've passed on the vis motor idea to Mick. He's home being ill right now, but sure when he's better he'll check them.
And we bought the new testing cable and software from reputable company. hoping it isn't faulty. We'll eliminate one thing at a time and hope to end up with a fully working moonshine.

desperatedan · 19th January 2015, 21:41

Quote:

Originally Posted by Anon3

For clarity, has this only come on since the LPG fitment?

You really need to seperate LPG from petrol, to sort this, at first thought.

Have you tried new twin electrode spark plugs specifically for LPG? Have you substituted the coil pack for a good known one? I had a duel fuel vectra that developed a lack of power on either fuel it was the coil pack.

19th January 2015, 20:12	#1
TamarHolley Regular poster MG ZT 190 SE Join Date: Jul 2014 Location: whiteley Posts: 62 Thanks: 9 Thanked 2 Times in 2 Posts	Any help please? Hesitating/backfire over 4000rpm Hi! I've put something about this under 'technical' but no response, so trying again here. (attention seeking behaviour, I know!) Moonshine had a replacement front end electrical kit, with new lpg ecu, etc. All worked great! Ran the diagnostic software, and she was working well. Except that when I drove home from workshop, the hesitates and backfires over 4000rpm. On lpg and petrol. We had a minor issue with one lambda, so disconnected it, hoping that would be the culprit. But it's not, as she still has same issue. So we're scratching our heads! Levels are fine. No leaks of fuel or exhaust. Compression normal. Timing normal. Plugs all fine, as are leads. Running temperature normal. sub4000rpm, works perfectly on petrol, changing over smoothly and normally to lpg. Smooth running on both fuels until hit that level. So, we're really hoping someone can shed light on what this might be?! Please!! __________________ [SIGPIC][/SIGPIC] Moonshine sunning herself outside Potters Heron, Hursley.

19th January 2015, 20:40	#2
Greeners Moderator MG-ZTT Join Date: Mar 2007 Location: Ware, Herts Posts: 19,798 Thanks: 161 Thanked 1,249 Times in 1,036 Posts	get the vis motors checked __________________ *David* Impecunity is the mother of ingenuity Useful how to's for common problems Car Of The Month Jan 2014 [SatNav Power Down] [Coolant Level] [SatNav Repair] [Diesel Non Starting] [Paint Codes] [Rear Light Seals] [Reversing Light Switch] [Bleeding Brakes][Sunroof Drain] [Early ZT's][Instrument Pack Diagnostics][ATC Diagnostics]

19th January 2015, 20:44	#3
TamarHolley Regular poster MG ZT 190 SE Join Date: Jul 2014 Location: whiteley Posts: 62 Thanks: 9 Thanked 2 Times in 2 Posts	OK. Will get back to you on that! But would that cause hesitate, misfire, and car go into limp mode? Worth checking anyway though. Thanks. __________________ [SIGPIC][/SIGPIC] Moonshine sunning herself outside Potters Heron, Hursley.

19th January 2015, 21:05	#4
Anon3 Posted a thing or two Rover 75 Join Date: Mar 2014 Location: Birmingham Posts: 1,394 Thanks: 199 Thanked 219 Times in 187 Posts	Odd at that sort of revs, but yes, power Vis came to mind for me too. __________________ [SIGPIC][/SIGPIC] Villa, Stella, Balti. It's Brummie latin that means, er...... Vis tester available to local V6 owners

19th January 2015, 21:09	#5
Anon3 Posted a thing or two Rover 75 Join Date: Mar 2014 Location: Birmingham Posts: 1,394 Thanks: 199 Thanked 219 Times in 187 Posts	For clarity, has this only come on since the LPG fitment? You really need to seperate LPG from petrol, to sort this, at first thought. __________________ [SIGPIC][/SIGPIC] Villa, Stella, Balti. It's Brummie latin that means, er...... Vis tester available to local V6 owners

19th January 2015, 21:18	#7
Anon3 Posted a thing or two Rover 75 Join Date: Mar 2014 Location: Birmingham Posts: 1,394 Thanks: 199 Thanked 219 Times in 187 Posts	Hesitance at these sort of revs is invariably weak mixture in my experience. I'd suspect poor software at first glance, but don't know the background. My first reaction would be to richen the mixture and see if it helps. If that doesn't help, I don't have a clue, I'm afraid. __________________ [SIGPIC][/SIGPIC] Villa, Stella, Balti. It's Brummie latin that means, er...... Vis tester available to local V6 owners

19th January 2015, 21:23	#8
Anon3 Posted a thing or two Rover 75 Join Date: Mar 2014 Location: Birmingham Posts: 1,394 Thanks: 199 Thanked 219 Times in 187 Posts	Ooh, sorry, Vis motor first __________________ [SIGPIC][/SIGPIC] Villa, Stella, Balti. It's Brummie latin that means, er...... Vis tester available to local V6 owners

19th January 2015, 21:31	#9
TamarHolley Regular poster MG ZT 190 SE Join Date: Jul 2014 Location: whiteley Posts: 62 Thanks: 9 Thanked 2 Times in 2 Posts	I've run her since I bought her in July, and she worked perfectly in lpg until November. Wasn't aware of her former lpg issues, so would be interested to hear about them! I've passed on the vis motor idea to Mick. He's home being ill right now, but sure when he's better he'll check them. And we bought the new testing cable and software from reputable company. hoping it isn't faulty. We'll eliminate one thing at a time and hope to end up with a fully working moonshine. __________________ [SIGPIC][/SIGPIC] Moonshine sunning herself outside Potters Heron, Hursley.