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1995-2002 Range Rover P38A
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11 Posts
Discussion Starter #1
Hello All,

I've had a issue recently which I've used these forums to help trouble shoot so I thought I should add my experience in case it may help others.

I have a 1999 diesel (with EGR), manual gearbox P38 thats now covered 168K miles. In the last few weeks its been suffering an intermittent loss of power, as if the turbo isn't working. It will slowly gain momentum, lets say, when the accelerator is depressed what feels like maybe an inch or so. If pushed down any further than this then its actually worse. Eventually on level ground it will get up to 50mph. Any hills mean its instantly slowing. This has been occurring roughly one in three starts. Sometimes it will cure itself after a few miles, and sometimes not. Luckily my route to work only consists of fairly flat A roads with loads of these new 40/50 mph speed limits which I'm normally happy to ignore, but now turn out to be a convenience :) so I've had time to work through things step by step. There are no warning lights and there is no smoke which to me indicates a lack of fuel. I'd discounted the in-tank fuel pump as this was replaced about 15K miles ago with an OEM version when the previous one packed up. I did swap the pump relay with a known good one just in case. This made no difference.

I then changed the MAP sensor and vacuum pipe as this seemed to be the most mentioned by a number of people as fixing things and the price of it wasn't too outrageous. In my case this didn't cure the problem. After more reading I tried disconnecting the MAF sensor, and in a week of driving and multiple starts the issue hasn't reoccurred. Today I cleaned the MAF sensor with electrical contact cleaner and reconnected it and the problem is back. My guess is that the ECU is getting conflicting messages from the MAP and a (hopefully) faulty MAF sensor and gets confused about what it should be doing.

A quick note about the MAF sensor. I'd read conflicting information on lessor forums about whether disconnecting the MAF sensor effects performance on a diesel P38 and I can say it absolutely does. While I can't tell much difference in peak power, its where that power becomes available that is affected. Its moved approximately 500rpm further up the rev range. Usually the power seems to start at around 1500-1600rpm. With the MAF disconnected this doesn't start until around 2000-2100 rpm.

My next step is to buy a new MAF sensor. I'll post when its fitted with the results.

Matt
 

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Registered
1995-2002 Range Rover P38A
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908 Posts
May be EGR valve stuck in open position. Better disconnect it for good.

In-tank effects will be above 80 KMPH and also when starting.
 

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1999 P38 vogue
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19 Posts
  1. Have you tried putting some 2 stroke oil in fuel filter and run it through ---- the pistons in diesel pump are titanium and can get sticky --- 2stroke oil cures it -- hope that helps you
 
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