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Discussion Starter #1
What would be the symptoms if the valley gasket hadn't been installed properly? and is there any tests for this?
 

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1995-2002 Range Rover P38A
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In my case, it was an oil leak down the back of the engine block.
 

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I'm going to guess the rear valley seal wasn't installed or clamped down properly. I have the same issue, but more due to clamp bolt threads being stripped. I haven't addressed it yet, just keep topping up the oil for now until I can get a timesert installed.
 

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Discussion Starter #4
So it wouldn't affect the running then? - I don't have any oil leaks from it, but someone had mentioned spraying something round the gasket to see if it burnt the spray to check for inlet leaks - was quite vague - am I barking up the wrong tree?
 

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The vally gasket, in addition to providing an oil seal, is also the lower inlet manifold gasket. So if this is leaking air this will not be accounted for by the MAF and can cause a lean mixture. This can lead to fault codes being thrown up about the O2 sensors.

So what are the problems you are getting?
 

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Discussion Starter #6
I'm not getting any error codes thrown up on the OBDII scanner, but the fuel trims are going wild on the right hand bank. They're going straight up to 25% which is the max, the left hand bank stays around 2-3% which I believe is normal. This is causing it to overfuel.

I've not had much of a look yet, but there is one cylinder which I think is losing oil - and that's on the right hand bank.

I'm presuming it's missfiring but it's hard to tell on a v8 - still seems quite smooth. Idle revs appear to be slightly low.

I put new spark plugs in and idle went correct at approx 800rpm, acceleration felt better and fuel trims stayed at below 5% for both banks for about 10 minutes then bank 2 went rich again.


It may just be down to the excess oil in the cylinder fouling up the spark plug and causing it to fail to spark, - would the ecu then squirt in more fuel? Or would the unburnt fuel just be seen as excess fuel trim? - I would have thought the ecu would see the excess fuel at the lambda sensor and try to reduce the fuel? Not increase it?


Anyway someone had suggested that a leaking inlet manifold would be hard to know was happening but could cause rich running. It was one thing I hadn't looked at. They said about spraying something flamable around - is that a good idea and what exactly am I testing for / looking for?

Thanks
 

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if the figure for the fuel trim is positive it means it is running lean not rich. the ECU is adding an extra 25% fuel to try to compensate for the lean readings the O2 sensor will be getting. This is often caused by an air leak at a gasket.

Have you tried reading live values for the O2 sensors.
Also when you say fuel trim are you talking about the short or long fuel trim?

If you spray something like start you b*stard around the inlet manifold if there is a leak the revs will momentarily rise. Just make sure you do outside.
 

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Discussion Starter #8
That sounds like what I was told - it's slowly coming back to me now! I was working on the range rover over winter and just haven't had time to look at it recently so it's been over 3 months since I looked at it and I'm trying to get myself prepared to look again.

Yes from memory it was +25% so for whatever reason it thinks it is running lean and pumps in more fuel so in actual fact it is running rich.

You mention an air leak at a gasket would cause this - which gasket or gaskets?

Live o2 sensor values were tested - but I can't remember the outcome, I think they gave perfectly accpetable values to match what was going on, o2 sensors were also swapped round and the figures stayed on the same side.

I'm talking short term fuel trim, long term keeps getting reset by leaving the battery off etc.

I've got some easy start somewhere or some isoproal alcohol - would either of these do? Is it likely to cause any flames should I have the fire extinguisher at the ready?
 

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sotal said:
Yes from memory it was +25% so for whatever reason it thinks it is running lean and pumps in more fuel so in actual fact it is running rich.
If there was a problem with the O2 sensor that may happen, but if you have an air leak then it will be running lean, the O2 sensor picks this up and increases the fuelling to try to bring it back normal. Any air leak post the MAF will cause this, but if only one bank affected then an air leak on the manifold for that side would be most suspect.

sotal said:
You mention an air leak at a gasket would cause this - which gasket or gaskets?
errr - valley gasket,
or possibly the upper inlet manifold gasket.

sotal said:
I'm talking short term fuel trim, long term keeps getting reset by leaving the battery off etc.
Pretty sure the long term adaption remains even after battery removed - hence the need to reset the adaptive values using T4 or Blackbox

sotal said:
I've got some easy start somewhere or some isoproal alcohol - would either of these do? Is it likely to cause any flames should I have the fire extinguisher at the ready?
easy start will be ok - don't know about the alcohol - really need something that is a gas (propane can be used) or something that changes to gas like the easy start. Shouldn't be any flames. Do a small section at a time and having an extinguisher would be a sensible precaution
 

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Discussion Starter #10
Yes I've read on here a lot that the long term fuel trim needs to be reset with a proper diagnostics, but mine keeps getting reset. I'm not 100% sure if it was the battery being off or there is an option in EasyOBDII (software) which allows a reset of the fuel trims (again people on here have said it won't work but it does!)

It's not nice to drive after it resets and tends to stall everytime I stop for the first few miles, then gets better.

I'll give the EasyStart a try and see what happens
 
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