P38A 2001 4.6 emissions

It has failed its emissions test at MOT on CO excessively high something like about 5.5 on petrol (it was difficult last year to get through), HC were under the 200 mark. It has LPG and that runs OK and its emissions are fine on LPG which is what I suspected.

It blew a cylinder head gasket about 8 months ago and now wondering if (one of ) the CATs were damaged. It had new plugs and leads at the time too.

It has 180k miles but engine replaced some years ago (don't know when). Its mint inside the engine (both heads were cleaned anyway whilst off), does not burn oil, pulls like a train, has clean oil and clean air filter. I had the injectors cleaned and tested about when the heads were off and all were within about 5% of normal and they were all cleaned. It has new air filter too this week again.

Cant find any inlet manifold air leaks. It has had two new O2 sensors and rear tailpipe exhaust silencers were replaced due to crack near Y piece before test. PS did not do any map resetting, my Faultmate MSV only shows drive cycle required

MAF sensor looks OK, and clean. Camshaft sensors is in fault (p1000 I think) have changed it twice but no avail, understand its likely to be residual magnetism to the cam sprocket necessitating a stripdown again so not doing that. Only other issue is one slightly noisy tappet at tickover.

I think its over fuelling in petrol

So only thoughts now are :-
1) CATS (may be damaged by head gasket failure with coolant, or may be just old now - don't know if ever replaced)
2) Engine coolant temp sensor (understand there is a separate one for the gauge) and the gauge reads OK,
3) Coil packs (but don't believe so since the HC are reasonably OK)
4) MAF
thoughts on whats best to do now as at a bit of a loss.
Mark

Diag would tell you better without guessing.

I thought the tester was only obliged to test it on the fuel it was running on when it came in for test?

DanClarke said:

I thought the tester was only obliged to test it on the fuel it was running on when it came in for test?

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agree and that's how I have my test, BUT, I still want the petrol related emissions sorting though since there is some other underlying problem.

DanClarke said:

I thought the tester was only obliged to test it on the fuel it was running on when it came in for test?

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nothing showing up on diagnostic other than P1000 camshaft sensor and Pxxx drive cycle required (but that's likely because I have since had the battery disconnected).

I often wonder about the accuracy of emission read-outs during a MOT. My RRC (V8 auto) has just passed it's test with no advisories but examining the E results reveals a lower figure than previous years … not that I'm complaining, but surely as an engine ages you would expect the figures to gradually rise? It is a low mileage car only covering around 2k miles per annum & regularly serviced but there must be a degree of wear taking place?

norseman said:

I often wonder about the accuracy of emission read-outs during a MOT. My RRC (V8 auto) has just passed it's test with no advisories but examining the E results reveals a lower figure than previous years … not that I'm complaining, but surely as an engine ages you would expect the figures to gradually rise? It is a low mileage car only covering around 2k miles per annum & regularly serviced but there must be a degree of wear taking place?

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agree, I would too expect that it would naturally increase, however, O2 sensors and CATs should I would also expect take care of this in closed loop control.

hi, the law states that whatever the vehicle's fuel is being used on presenting it for test at m.o.t. station , then the emissions test side must be set at the same ,,,,i.e. petrol = petrol emission !!!!! lpg = lpg emission . so to break it down the tester must identify before diag test wich fuel is set on vehicle . he cant assume that its petrol or lpg ,, a lot of testers depending on experience have never seen a lpg , set up !!!!! and personal experience a few years ago same happened to me , it was soon sorted !!!!!!! so follow the law .

norseman said:

I often wonder about the accuracy of emission read-outs during a MOT. My RRC (V8 auto) has just passed it's test with no advisories but examining the E results reveals a lower figure than previous years … not that I'm complaining, but surely as an engine ages you would expect the figures to gradually rise? It is a low mileage car only covering around 2k miles per annum & regularly serviced but there must be a degree of wear taking place?

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methinks you should give your chauffer a rise and compliment him on his driving abilities !!!!!!!!!! or get him to doff his cap more ,,,,,

mozz smith said:

hi, the law states that whatever the vehicle's fuel is being used on presenting it for test at m.o.t. station , then the emissions test side must be set at the same ,,,,i.e. petrol = petrol emission !!!!! lpg = lpg emission . so to break it down the tester must identify before diag test wich fuel is set on vehicle . he cant assume that its petrol or lpg ,, a lot of testers depending on experience have never seen a lpg , set up !!!!! and personal experience a few years ago same happened to me , it was soon sorted !!!!!!! so follow the law .

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Fine, I understand about what fuel it is tested with, really I do and I have no problems with that or my testing stations application of the law. Please that is NOT my problem.
My problems is it can pass a test on LPG and it cant pass a test on Petrol. I want to be able to repair the vehicle so that it WILL pass on petrol so it does not matter which fuel mode I present it in. With all due respect, please no more statements about getting it tested in one mode or the other.

It may not be throwing codes, but have you looked at live data? Is it sitting on borderline values?
p.s. Did you know that the tester has to test it on the.... Oh..

mmmmmm your problem is " it cant pass on petrol " we know , you stated that in your first post !!!!! so in future set your question's properly .instead of going round the houses or in your case you cant cos its failed its m.o.t. happy new year .

When were the cats replaced last?

So I take it you are referring to CO, this is produced usually because of a rich mixture. But yet you say you got a pass on HC, by how much?
Was the car up to correct temp on test? And I don’t mean on the gauge,(it’s brain needs to know)
Is it going into closed loop not sure if you can tell this on your Faultmate (but think so).
Do you drive it a lot on the Lpg?
Why is your Faultmate saying “drive cycles required” have you been in and changed settings recently?
I would certainly be checking a lot before having to change cats.

J

marjon said:

Why is your Faultmate saying “drive cycles required” have you been in and changed settings recently?

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I missed the comment about drive cycles....

DRIVE CYCLES - from 99MY

The following are the Testbook drive cycles

Drive cycle A:

1. Switch on the ignition for 30 seconds.
2. Ensure engine coolant temperature is less than 60°C (140°F).
3. Start the engine and allow to idle for 2 minutes.
4. Connect Testbook and check for fault codes.

Drive cycle B:

1. Switch ignition on for 30 seconds.
2. Ensure engine coolant temperature is less than 60°C (140°F).
3. Start the engine and allow to idle for 2 minutes.
4. Perform two light accelerations (0 to 35 mph) (0 to 60 km/h) with light pedal pressure).
5. Perform two medium accelerations (0 to 45 mph) (0 to 70 km/h) with moderate pedal pressure).
6. Perform two hard accelerations (0 to 55 mph) (0 to 90 km/h) with heavy pedal pressure).
7. Allow engine to idle for two minutes.
8. Connect Testbook and check for fault codes.

Drive cycle C1 (vehicles without advanced
EVAPS):

1. Switch ignition on for 30 seconds.
2. Ensure engine coolant temperature is less than 60°C (140°F).
3. Start the engine and allow to idle for 2 minutes.
4. Perform two light accelerations (0 to 35 mph) (0 to 60 km/h) with light pedal pressure).
5. Perform two medium accelerations (0 to 45 mph) (0 to 70 km/h) with moderate pedal pressure).
6. Perform two hard accelerations (0 to 55 mph) (0 to 90 km/h) with heavy pedal pressure).
7. Cruise at 60 mph (100 km/h) for 5 minutes.
8. Cruise at 50 mph (80 km/h) for 5 minutes.
9. Allow engine to idle for 2 minutes.
10. Connect Testbook and check for fault codes.

jmgtaylor said:

agree, I would too expect that it would naturally increase, however, O2 sensors and CATs should I would also expect take care of this in closed loop control.

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Mine is a '87 therefore no CAT etc.
That's why I like it

If a duel fuel vehicle cannot pass the MOT emissions test running on both fuels it should not be on the road.

marjon said:

So I take it you are referring to CO, this is produced usually because of a rich mixture. But yet you say you got a pass on HC, by how much?
Was the car up to correct temp on test? And I don’t mean on the gauge,(it’s brain needs to know)
Is it going into closed loop not sure if you can tell this on your Faultmate (but think so).
Do you drive it a lot on the Lpg?
Why is your Faultmate saying “drive cycles required” have you been in and changed settings recently?
I would certainly be checking a lot before having to change cats.

J

Click to expand...

ukadamwest said:

I missed the comment about drive cycles....

DRIVE CYCLES - from 99MY

The following are the Testbook drive cycles

Drive cycle A:

1. Switch on the ignition for 30 seconds.
2. Ensure engine coolant temperature is less than 60°C (140°F).
3. Start the engine and allow to idle for 2 minutes.
4. Connect Testbook and check for fault codes.

Drive cycle B:

1. Switch ignition on for 30 seconds.
2. Ensure engine coolant temperature is less than 60°C (140°F).
3. Start the engine and allow to idle for 2 minutes.
4. Perform two light accelerations (0 to 35 mph) (0 to 60 km/h) with light pedal pressure).
5. Perform two medium accelerations (0 to 45 mph) (0 to 70 km/h) with moderate pedal pressure).
6. Perform two hard accelerations (0 to 55 mph) (0 to 90 km/h) with heavy pedal pressure).
7. Allow engine to idle for two minutes.
8. Connect Testbook and check for fault codes.

Drive cycle C1 (vehicles without advanced
EVAPS):

1. Switch ignition on for 30 seconds.
2. Ensure engine coolant temperature is less than 60°C (140°F).
3. Start the engine and allow to idle for 2 minutes.
4. Perform two light accelerations (0 to 35 mph) (0 to 60 km/h) with light pedal pressure).
5. Perform two medium accelerations (0 to 45 mph) (0 to 70 km/h) with moderate pedal pressure).
6. Perform two hard accelerations (0 to 55 mph) (0 to 90 km/h) with heavy pedal pressure).
7. Cruise at 60 mph (100 km/h) for 5 minutes.
8. Cruise at 50 mph (80 km/h) for 5 minutes.
9. Allow engine to idle for 2 minutes.
10. Connect Testbook and check for fault codes.

Click to expand...

Hi, We have a 2007 RR HSE 4.4l petrol. I have been performing a drive cycle by driving @ 55mph for 5 minutes, coming to a complete stop without the brake pedal. Immediately followed by street driving @35mph with plenty of stop & go, coming to a complete stop, then slowly accelerating to 35mph for 35 minutes. Performed this procedure twice. In each case, all clear EXCEPT, evap monitor test in each case. Fuel was @ 3/4 tank. No P codes were shown.

Please help! I need to get my registration completed. Any help is GREATLY appreciated. Thanks, in advance.