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1995-2002 Range Rover P38A
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Discussion Starter · #1 ·
Hi all,

I am after some advise / other people experiences with reference to MOT failure with my P38 on emissions.

I have taken it to a local specialist who has the diagnostic equipment to talk to it,

It has no faults stored or present in GEMS

The CO2 at idle is between 7 and 8% leaning off to 1.5% if held at 3000rpm.

Lambda readings are 0.85 just under the .91 for MOT and 198PPM (mot pass) for Hydro Carbons @ 2900RPM

IAT, ECT, MAF, and (new) cats all working fine no problems no air leaks into exhaust and all was fine on previous MOT last year 1900 miles ago.

The only thing I noticed is on occasion it would almost cut out when trying to slow speed manouver into parking spaces etc. (probably due to over fueling) and lots of pressure when releasing the fuel filler cap? but this could be normal.

Any pointers would be helpful to pass back to the specialist

Thanks

Spen
 

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If it is running rich then this should be showing up in diagnostics, too, via the O2s (but if this is marginal or a new problem it can take a while for the codes to appear); What kit is your chap using ?

'Lots of pressure out the fuel cap' is wrong though and points to an EVAP issue.
 

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1995-2002 Range Rover P38A
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Start by treating it to a new set of spark plugs and a new air filter. HC is on the high side unless the engine is really tired and burning oil. The kit being used will be the standard MoT testing kit irrespective of who made it.
 

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Yes, I did mean the diagnostic kit (not the MOT station kit): The point is 'some fault code readers are better than others' with P38s but Snap On should be fine; Again it can take numerous 'drive cycles' for problems to show up, (if you did not already) see:-

http://www.rangerovers.net/forum/12...agnostic-trouble-codes-gems-drive-cycles.html

- As you can see it takes a while for DTCs/Fault Codes to clear - and basically a while for a lot of them to show up too (and the '96 does not have 'pending code' facilities like later cars)

That's why I asked 'How long has this problem existed' ? (and if a while, ball park, what is the mpg now, to give an idea of the degree of overfuelling as it sounds slight). BTW Lambda pass is .97

As you have some new cats fitted perhaps they disturbed the O2 sensors (?)- and so I would start by checking the outputs on these.
 

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1995-2002 Range Rover P38A
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Discussion Starter · #7 ·
Ok so after another call to the garage they told me that the iat sensor is reading -36degrees C on live data. Surely that can't be helping!!! But nothing else looked out of place allegedly ?

The mot fail cert said 0.91 but I suppose it could be 0.97
 

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1995-2002 Range Rover P38A
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Check the wires going into the plug that connects to the IAT sensor. Moisture can get under the insulation and rot the copper strands away so it looks OK but if you pull on the wires, only the insulation is holding it together. You can cut the top of the plug away and solder the wire directly to the back of the contact pin if that is the problem. If the engine ECU thinks the incoming air is that cold it will richen the mixture which would explain the emissions problem.
 

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Discussion Starter · #10 ·
It started miss behaving in September did about 400 miles then MOTd in November as wanted to see if would need anything. Has done 156 miles since. Has only covered 1700 miles between tests last year which it past with tyres and cats rattling as an advisory notes.
 

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Discussion Starter · #11 ·
Thanks Gilbert. I worked on the service desk for a main dealership when these were sold new. And most of the P38s we saw ran for thousands of miles problem free provided they were maintained correctly. And having owned several Classics before I really wanted one of these. Does anyone know a good man that can for these in the Portsmouth Hampshire area?
 

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I'll second that, mines at 291,953 miles at the moment. Admittedly I'm going to be spending tomorrow under it changing the rear diff but I don't think it's done too bad to last this long. I've had the wires rot through and had to solder them on the IAT sensor and also on the engine temp sensor (the one that feeds the gauge on the dash not he one that talks to the engine ECU). Can't help you with anyone in your area though I'm afraid.
 

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Discussion Starter · #13 ·
Yes some we saw from pdi upto over. 220000 miles in under three years! Although on the flip side we did have a Westminster on which the engine let go after only 49 miles. The customer didn't even make it home! Some of my old colleagues love them others hate them and tell me I get what I deserve if I bought one ! However comments like that aren't helpful in fixing it :confused:
 

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Ok so after another call to the garage they told me that the iat sensor is reading -36degrees C on live data. Surely that can't be helping!!!
Yes, as then the rig thinks it is (very !) cold and fuels accordingly (and may even keep the ECM in 'Open Loop'). Again IAT failure takes a while a show up as a DTC, but if the garage is also using Live Data then it means they are also monitoring the O2s and associated Trims (which will show up the degree of overfuelling, anyway). Either way sounds like they have located the fault now (?)

MOT Lambda 'pass' is actually 0.97-1.030, interesting that a duff IAT could drag it all the way down to 0.85.

Also interesting to note that engine you mentioned which gave way at 49miles... Yikes ! (but at least under warranty, bet the owner was unimpressed). Do you recall just what was wrong with it ?

To be fair these earlier rigs do have some diagnostics 'quirks' but using Live Data gets around them.
 

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Discussion Starter · #15 ·
Yes one of the con rod big ends hadn't been done up to correct torque and let go jamming itself into the block and stopped the crank! The customer was very understanding as it was his fifth Range Rover. However he did move onto a Porsche cayenne three years later.
 

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"it would almost cut out when trying to slow speed manouver into parking spaces etc."

Air Idle Control stepper motor prob?
 

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Yes one of the con rod big ends hadn't been done up to correct torque and let go jamming itself into the block and stopped the crank! The customer was very understanding as it was his fifth Range Rover. However he did move onto a Porsche cayenne three years later.
Good grief ! See the customer finally stopped 'understanding' though !
 

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Discussion Starter · #19 ·
Hi I'm still no further ahead with this as the garage are now trying things manually??? Can the ecu be reset at all as they're starting to suspect the ecu or are they plug n play?
 

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Most definitely not plug and play, more plug and no start as the ECU has to be synchronised to the BeCM. With a dedicated LR diagnostic tool, it is possible to reset the adaptive values but if the ECU is still seeing low intake air temperature, it will immediately adjust back to what it thinks is correct and you are back at square one.

It isn't rocket science. If they check the two wires from the IAT sensor back to the ECU for continuity and if that is OK, then it needs a new sensor. Unfortunately for many mechanics, as electric things don't go up and down or round and round, it's a black art.
 
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