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Discussion Starter #1
Around 6 months ago I added to my family's collection of Range Rovers (now 6 between 4 of us, I think it's genetic) by buying a '98 P38 4.6, 160,000ks (100,000 miles). My first.

When I got it I went about some basics; plugs, plug leads, oil and it ran perfectly, with the odd gremlin here and there that I have been able to sort out thanks to this forum. However 6 months after that and about 5,000Ks (I don't drive it that often), it has developed a fairly serious flat spot and noticeable power loss under acceleration, a slightly rough idle (not serious) and generally lacking in responsiveness. It bogs down when you quickly press the go pedal. There are no check engine lights on. Also according to the trip computer it can use a lot of petrol when driving aggressively (55L/100ks or 5 mpg), when taking it easy it is fairly normal 13-14 L/100ks highway)


Here is what I have done so far after reading through this forum:

Having only recently done the plugs and leads I figure that isn't the problem. Sent to a friend's shop (not a RR specific one), he said it was running a bit rich, but didn't get any fault codes.

I read some fault codes on a OBDII reader we had at home and got P1138 (Oxygen sensor problem with switching lean, sensor(s) for Bank A Y C), I switched the sensors, reset the codes, drove it, then got the same code. So my guess is it isn't an O2 sensor otherwise the fault would have moved to Bank B. I also got some pending codes (P3999 *2), but as far as I can tell they don't mean anything.

MAF, cleaned it using MAF cleaner, no difference, switched with Brother's MAF from his 96 P38, no difference.

Ran some injector cleaner through 2 tanks of fuel. I doubt this stuff really works that well but I figured it couldn't hurt.

Other things i have noticed, PCV tube running up next to the throttle was drowned in oil and gunk, I cleaned both. A bit of oil and gunk build up around the throttle, which I cleaned up with some WD40, without taking apart the whole thing (I might try that down the track). An intermittent rattle is coming from the CAT on the same side as Bank A (Passenger side RHD), not sure if it is related.

I'm now running low on cheap ideas to fix this and will probably have to send it off to somewhere that knows these and has all the right machines for testing it, and re-mortgage the house in the process. Has anyone here had similar problems, or any ideas I can try?

Other things I have thought of but havn’t been able to try just yet, i'm not sure if these would actually cause my problem but this is the direction I am heading in next.

Temp sensor
Injectors
Vacuum leak
CAT blocked
 

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2002-2005 Range Rover MkIII / L322
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Demon said:
Temp sensor
Injectors
Vacuum leak
CAT blocked
My next step would be the cats. If it's legal where you live, just cut em out and see how she runs. You can always put some new ones back on later.

Injectors are pretty easy to change, but it's so rare to see one go, I just doubt that's it. Have you pulled the plugs lately to see if one or more looks fouled? I'm wondering if you have a head gasket leak and you're burning through a bit of water in one cylinder.

It's possible also that you got a crappy set of wires, and one is arching already. Maybe run it in the pitch black garage and look under the hood to see if you can see any blue sparks. :think:

Good luck.

-Mag
 

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Before you send it out, couple other cheap fix ideas:

You mentioned oil change, but I wasn't sure if you've changed all oils ie transmission and transfer case. Dirty transmission oil affect how the car responds as well as mpg.

What kind of plugs did you get? I hope it was quality OEM spec ones. If not, you might want to get new ones.

Doesn't hurt to clean your injectors. Have you tried stuff like Redline's fuel conditioner?
 

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ghind said:
Does your cruise control work? A vacuum leak can do at least some of the things you mentioned.
The cruise won't affect anything here as it is a completely separate system and doesn't connect in to the inlet manifold.
 

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I do have exactly the same case.
An indy told me to replace the engine temp sensor because it looks like the engine computer thinks the temp is always cold so it richens the mixture.

I'm waiting for my sensor.
 

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also replace the vacuum line to the fuel pressure regulator, it's only 6" long and kind of buried so often gets missed.
 

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Discussion Starter #8
kmagnuss said:
My next step would be the cats. If it's legal where you live, just cut em out and see how she runs. You can always put some new ones back on later.

-Mag

Got it in 1. Turned out to be a blocked cat, didn't have time to get a new Cat put in before it's first weekend off road so I unbolted the flange to the muffler and jammed a rod into it, luckily the blocked cat was on the passenger side (RHD) so it was possible because of the shape of the exhaust system. Not sure exactly what I did to it in the end but it wasn't loose or blocked any more.

I guess the pressure in the exhaust system threw the reading on the o2 sensor, it also blew a whole lot of oil out of everywhere around the engine, where previously there were no leaks.

Ran perfectly the whole weekend, great on and off road these things. Now I just have to fix the cat properly.

Useful place this site, took only 1 post.

Thanks for the advice.
 

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I believe cats are not mandatory on those rigs in Australia.
Many of them do not even have lambda sensors.
If it's true, you could have a direct pipe welded in place, you'll get better economy
 
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