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Author Topic: failed mot emissions  (Read 823 times)

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swordfish

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failed mot emissions
« on: 31 May 2018, 15:27:58 »

looking for ideas ,, 2.6 v6 failed mot on  emissions at fast tick over ,, one thing i have noticed is there does not seem to be  cold start working from cold and it has a very slight rough tick over . 
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dave the builder

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Re: failed mot emissions
« Reply #1 on: 31 May 2018, 15:42:22 »

do you have a print out of the readings ?
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Bigron

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Re: failed mot emissions
« Reply #2 on: 31 May 2018, 16:57:01 »

I have found that a dose of Cataclean, a tankful of Shell V-|Power and a damn good thrashing  (NOT Basil Fawlty style!) reduces the emissions to sub-MOT level.  :)

Ron.
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Kevin Wood

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Re: failed mot emissions
« Reply #3 on: 01 June 2018, 13:06:29 »

If it's already not running well, then it points to a fault, IMHO.

Is the EML on? Are there any codes stored?
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swordfish

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Re: failed mot emissions
« Reply #4 on: 01 June 2018, 15:43:10 »

co mot fail
fast idle test fail 2.250%
second fast idle test fail 5.828%
natural idle test fail 6.478%

no warning lights on
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Nick W

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Re: failed mot emissions
« Reply #5 on: 01 June 2018, 15:47:27 »

Check all the intake pipes and hoses for leaks.
But do it as part of fitting a new thermostat.
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dave the builder

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Re: failed mot emissions
« Reply #6 on: 01 June 2018, 16:08:58 »

If the wet stat is stuck open, as Nick W says ,the ecu will fuel for cold start .
If you can get live data that helps ,cheap obd2 scanner /torque app ,that naughty scanner  :-X or similar
see what the ecu coolant temp sensor is showing .
vauxhalls over fuel when cold (or the ecu thinks it's cold )
a duff cts coolant temp sensor can read -40 degrees  :o
you will also be able to see stuff like lambdas switching and all that good stuff
cataclean I have used many times , I tend to put cataclean in a week or so BEFORE mot in 1/4 of a tank of fuel, use it till the light comes on , then , fill with fresh petrol.

getting the cat nice and hot BEFORE emissions test helps alot  ;D

check exhaust for blows (even small ones) check breathers and air intakes for leaks /blockages
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swordfish

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Re: failed mot emissions
« Reply #7 on: 04 June 2018, 14:57:38 »

just thought i would add the car will not reach full revs under load it starts to misfire
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Kevin Wood

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Re: failed mot emissions
« Reply #8 on: 04 June 2018, 15:20:06 »

co mot fail
fast idle test fail 2.250%
second fast idle test fail 5.828%
natural idle test fail 6.478%

no warning lights on

That's running very rich.  :o

As said, need to check live data, to see if the ECU temperature sensor is reading OK and, if so, check the other inputs to the ECU.
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swordfish

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Re: failed mot emissions
« Reply #9 on: 05 June 2018, 14:47:01 »

were is the thermostat temp sensor .
thankyou
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Doctor Gollum

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Re: failed mot emissions
« Reply #10 on: 05 June 2018, 16:15:10 »

were is the thermostat temp sensor .
thankyou
Thermostat is it's own temperature sensor ::)

ECU one is next to the dash one on the coolant bridge... Plug is identical to the purge valve (on back of 135 head) but voltages are different... Ecu one is 5v, purge valve is 12v, but both plugs reach both items...

ECU temp will be showing as - 40 on diagnostic gubbins ;)
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swordfish

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Re: failed mot emissions
« Reply #11 on: 05 June 2018, 19:42:41 »

so that's the one with 2 wires going in to it blue plug .
thankyou
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swordfish

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Re: failed mot emissions
« Reply #12 on: 06 June 2018, 14:13:02 »

Hi,, just come across a round black sphere about 2" long nr the temp sender with a 2 wire plug  . one blue and one grey and what looks like a vacuum nipple. but its not connected to anything and there is no vacuum pipe connected . any body no if and what it should be connected to .
thankyou
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Doctor Gollum

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Re: failed mot emissions
« Reply #13 on: 06 June 2018, 14:26:32 »

That's the purge valve ::)

One pipe goes to breather bridge, tother to the tank behind the driver's wheel arch.

If it wasn't connected to the breather bridge I am not surprised it won't idle right ;D
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Re: failed mot emissions
« Reply #14 on: 06 June 2018, 14:34:29 »

its broken off at the bracket end ,, but problem is there is no pipework
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swordfish

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Re: failed mot emissions
« Reply #15 on: 06 June 2018, 14:38:06 »

it seems to have been bypassed the pipe from the drivers wheel arch goes direct to the bridge will it still run correctly  :-\ :-\
thankyou
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Doctor Gollum

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Re: failed mot emissions
« Reply #16 on: 06 June 2018, 14:39:35 »

Clearly not ::)
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Re: failed mot emissions
« Reply #17 on: 06 June 2018, 14:48:42 »

ok thankyou , what does this vacuum sphere do 
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Doctor Gollum

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Re: failed mot emissions
« Reply #18 on: 06 June 2018, 14:50:49 »

Right, do the following, in order and report back...

1. Turn ignition to 2.
2. Measure the voltage at both plugs. 1 will be 5v, the other 12v. Label them.
3. Turn the ignition off and pull the key.
4. Buy a new ecu temp sensor.
5. Fit new ecu temp sensor and plug the 5v plug to it.
6. Fit the 12v plug to the purge valve.
7. Obtain and fit the plumbing from the tank to the purge valve and from the purge valve to the breather bridge.
8. Refit everything else currently removed.
9. Triple check all the vacuum and breather hoses, including at the front of the engine.
10. Re present the car for its MoT.
 :-X
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swordfish

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Re: failed mot emissions
« Reply #19 on: 06 June 2018, 14:56:34 »

ok thankyou . in that case i will need to buy a new purge valve as the back has broken off it were the pipe connects
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Kevin Wood

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Re: failed mot emissions
« Reply #20 on: 06 June 2018, 16:19:48 »

As a test that this is your (only) problem, if you disconnect the pipe to the wheel arch canister and block the resulting empty hose barb on the breather bridge, it should then idle better.
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swordfish

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Re: failed mot emissions
« Reply #21 on: 06 June 2018, 16:49:33 »

ok thanks ,., just tried that and no difference. when you start from cold the engine revs are low.  :-\ :-\ usually when you start from cold the engine revs are higher due to the cold start operating
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swordfish

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Re: failed mot emissions
« Reply #22 on: 12 June 2018, 09:47:33 »

HI,,  ok passed the mot emissions . but its still misfiring at high rmp it then continues to misfire on what feels like 3-4 cylinders and then as you drive at lower speeds it gradualy comes back on 6 cylinders     :-\ :-\
any ideas
thankyou
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Doctor Gollum

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Re: failed mot emissions
« Reply #23 on: 12 June 2018, 11:47:42 »

Coil packs, contaminated plug wells (oil/water), knackered or fouled plugs, or a wiring fault...

Which depends on which cylinders are mis firing... Car can tell you that. ;)
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Re: failed mot emissions
« Reply #24 on: 12 June 2018, 11:51:12 »

ok thankyou , drivers side coil pack  :y :y
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swordfish

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Re: failed mot emissions
« Reply #25 on: 12 June 2018, 11:54:29 »

this particular 3.2 omega has got the earlier exhaust and cats fitted  from a 3.0 so only uses 2 lambda sensors  :o :o is there any reason somebody would do this
Thankyou
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Kevin Wood

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Re: failed mot emissions
« Reply #26 on: 12 June 2018, 11:56:50 »

It may have needed new cats and only the 3.0 style were cheaply available, or maybe someone thought they'd be less restrictive.

If you don't have post-cat sensors fitted, then you will never have a happy ECU, so I assume the engine management warning light has been removed, or is constantly on (which is now an MOT fail).
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Re: failed mot emissions
« Reply #27 on: 12 June 2018, 12:00:01 »

Hi,, yes now and again the engine warning light comes on , will it affect the performance missing the sensors
thanks
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Re: failed mot emissions
« Reply #28 on: 12 June 2018, 12:42:38 »

If the two post cat lambda sensors are not there I would have thought the eml would be constantly on .registering various faults such as heater coils,lack of action etc so I wonder what they have actually done. Is there anything plugged into where they should be ?.these donít usually respond well to o2 imitator modules and usually only work by moving the second sensor post main cat. As you sure they are not fitted just not in sight ?
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Re: failed mot emissions
« Reply #29 on: 12 June 2018, 12:45:23 »

Yep, I'd also expect a constant EML. It's possible they have been fitted to the 3.0 cat sections or that the sensors are still connected but not fitted to the exhaust.

They only perform a monitoring role, but not having them fitted means you won't find out about any other faults, as they will be masked.
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Re: failed mot emissions
« Reply #30 on: 12 June 2018, 13:42:58 »

the car did belong to jamescdx he did the conversion
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