Emissions

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hughandjen

Active Member
Posts
95
Location
Kendal
P38 4.6 1999 Thor engine

hi guys my P38 had a Turner engineering fully reconned engine a few years ago by previous owner only done 8k miles since then.
Passed its MOT last year and sailed through its emissions

Fast Idle
CO 0.04%..........Pass
HC. 7ppm............Pass
Lambda. 1.000.....Pass

I bought the car a few months ago. All the time I’ve had it it has had a loud ticking noise at all revs. I’ve not been able to identify the source of the sound but suspect it may be the exhaust manifold on the passenger side.
it failed it’s MOT this week on emissions after only 2k miles since last MOT

Fast idle first test
CO. 0.49% .........Fail
HC. 117 ppm......Pass
Lambda 1.000.....Pass

second fast idle test
CO. 0.72%...........Fail
HC. 19 ppm........Pass
Lambda. 0.99.......Pass

natural idle test
CO. 0.11%..........Pass

First question is if there is a leak in the manifold could this cause this MOT failure
Secondly if it isnt the exhaust any ideas where I should look?

plugs all look a good colour.

thank you
 
Yes, exhaust leak might lead to oddities. Head gasket failure can also cause ticking noise but as you say, more likely to be exhaust. Need to fix the tick first before looking at o2 sensors and so forth.

Strip of bog paper on a stick might give away the blow if you have a large stash left from lockdown 1. UV due in the coolant and then check the dipstick with a UV torch might give away HG failure.
 
Grrrrrr said:
Yes, exhaust leak might lead to oddities. Head gasket failure can also cause ticking noise but as you say, more likely to be exhaust. Need to fix the tick first before looking at o2 sensors and so forth.

Strip of bog paper on a stick might give away the blow if you have a large stash left from lockdown 1. UV due in the coolant and then check the dipstick with a UV torch might give away HG failure.
Click to expand...
Great advice thanks. That’s my job for today
 
If there is a leak before the first lambda sensor the engine can't get an exact picture of the emissions and adjust the mixture to suit. Here in France if there is a leak In the exhaust anywhere they won't give a result as the system isn't evacuating the gas as it should therefore the procces is compromised.;)
 
Hi guys an update
Can’t find a trace of an exhaust leak. I have used a engine stethoscope and I think the noise is coming from the passenger side rocker cover so could be a stuck valve lifter. Would this cause my emissions issue??
Did a compression test on all cylinders and the passenger side bank were 130, 127, 131, and 135 psi
The other side are 135, 135, 130, 130
All plugs are a good colour with no dampness at all
 
hughandjen said:
Hi guys an update
Can’t find a trace of an exhaust leak. I have used a engine stethoscope and I think the noise is coming from the passenger side rocker cover so could be a stuck valve lifter. Would this cause my emissions issue??
Did a compression test on all cylinders and the passenger side bank were 130, 127, 131, and 135 psi
The other side are 135, 135, 130, 130
All plugs are a good colour with no dampness at all
Click to expand...

They're all very similar so I would say compression fine. Guess it could be a rocker. I'd be tempted to try the UV dye as it is easy!
 
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