urgent...Running rich for Mot

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urgent...Running rich for Mot

Post by 8bit-ash on Mon Jul 28, 2014 2:41 pm

Hi all,

I'm sitting on the mot car park. Vans just failed on high hydrocarbons. I've done a oil, plug and italian tune up already. Is it easy to change the mixture without plugging it up to anything? 1.3.

Ta
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Re: urgent...Running rich for Mot

Post by Logi on Mon Jul 28, 2014 4:51 pm

Air filter out?
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Re: urgent...Running rich for Mot

Post by HighlyJetted on Mon Jul 28, 2014 9:08 pm

Most likely to be caused by:-

TPS sensor, MAP sensor, or Lambda sensor.

Did it fail on the idle or fast idle test, or both?
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Re: urgent...Running rich for Mot

Post by 8bit-ash on Mon Jul 28, 2014 10:43 pm

I'm not sure what it failed on, my printed sheet was for LPG and just says it failed on HC. The MOT guy switched it to petrol and tried that but I think he said it failed on both idle and fast with petrol.
I fitted that stainless Decat I bought off you and presented it on LPG thinking it would be OK. The mot guy didn't seem bothered about trying to get it through on petrol without a cat.
Any idea if a decated 1.3 would scrape through a test on petrol?

I also noticed after the MOT that one of my ignition leads had the top of an old spark plug still jammed in the top so it wasn't fitting very well. Couldn't really notice a misfire but there had definitely been some arcing in the tube as there was some rusty type deposits.
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Re: urgent...Running rich for Mot

Post by HighlyJetted on Mon Jul 28, 2014 11:09 pm

From the MOT testers handbook:-

"Vehicles which run on more than fuel (eg petrol and LPG) should be tested on the fuel they are running on when presented.
There is a slight difficulty with LPG vehicles: the hydrocarbons are propane rather than hexane. So the HC reading obtained must be divided by the propane/hexane equivalency factor (PEF) marked on the gas analyser. For example:
An LPG vehicle gives a HC reading of 700 ppm.
The PEF marked on the machine is 0.48.
So the actual MOT value is
700/0.48 = 1458 ie fail.
Some exhaust gas analysers have an automatic facility for doing this."

And a little post for thought

http://www.pistonheads.com/gassing/topic.asp?t=1062264
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Re: urgent...Running rich for Mot

Post by 8bit-ash on Mon Jul 28, 2014 11:13 pm

Yeah I found that link up earlier but the analyser states the vehicle is running on LPG and shows the appropriate fail figures.
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Re: urgent...Running rich for Mot

Post by HighlyJetted on Mon Jul 28, 2014 11:24 pm

What was it like on CO, CO2, NOx?

If its just high on HC's then suspect a misfire or poor ignition or incorrect timing.
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Re: urgent...Running rich for Mot

Post by scotia on Tue Jul 29, 2014 6:06 am

8bit-ash wrote:
Any idea if a decated 1.3 would scrape through a test on petrol?

no it wil not.
i tried to with an empty cat.
it had 6.0 with it and later when i replaced it with a charadecat 0.3  Laughing 
idle was fine but when revving it uup/fast idle was when it failed.
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Re: urgent...Running rich for Mot

Post by 8bit-ash on Tue Jul 29, 2014 7:46 am

HighlyJetted wrote:What was it like on CO, CO2, NOx?

If its just high on HC's then suspect a misfire or poor ignition or incorrect timing.

I passed all the others fine on LPG, just he HC sky high. I'm thinking now ive sorted the ignition lead, get a back box and refit the old cat and try again should hopefully then get through on petrol.

Is there any way of tricking a faulty sensor just for a pass? problem I have is i'm now in London til Thurs night when i'll then have to go back to suffolk where the van is and have it ready for a reMOT Friday lunch time to go away in it Friday afternoon. So no time for buying sensors if faulty.
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Re: urgent...Running rich for Mot

Post by HighlyJetted on Tue Jul 29, 2014 11:56 am

I have a tub full with MAP, TPS and IAT sensors.

If you need anything just call and we can get them sent out.
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Re: urgent...Running rich for Mot

Post by bushwhacker on Tue Jul 29, 2014 5:04 pm

HighlyJetted wrote:From the MOT testers handbook:-

"Vehicles which run on more than fuel (eg petrol and LPG) should be tested on the fuel they are running on when presented.......

Puzzled by this.

Presented mine for MOT earlier this year, running on LPG (as always), same MOT station I always use, got it back running on LPG but they tested it as petrol! I wondered whether there had been some change so that they have to be tested on petrol but since it passed I didn't take it any further.

It has created an oddity in that the online MOT record has one entry showing that it has been changed to lpg and the next entry showing that it has been changed to petrol! (Obviously don't believe everything these MOT records tell you).

The other thing was that, unusually, I was not given an emissions printout. Are they still supposed to be providing these?
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Re: urgent...Running rich for Mot

Post by HighlyJetted on Tue Jul 29, 2014 11:50 pm

I think so yes.

But a friendly tester might just wing it.
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Re: urgent...Running rich for Mot

Post by 8bit-ash on Wed Jul 30, 2014 7:30 am

HighlyJetted wrote:I have a tub full with MAP, TPS and IAT sensors.

If you need anything just call and we can get them sent out.

Hey did you get my PM?

Cheers
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Re: urgent...Running rich for Mot

Post by HighlyJetted on Thu Jul 31, 2014 8:47 am

I did yes, just got distracted before I replied. Work is crazy busy this week.

They could go today Royal Mail 1swt class.
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