Defender performance issues

Before I get going I accept that a Defender is never going to be a fast vehicle but I think I have some problem or problems and would welcome some advice on where to look.

Some background; it's a 110 station wagon on 1996 vintage with 181,000 miles on the clock. I have owned it for 8 years. It has always had a fair bit of black smoke on acceleration - more than usual according to pretty much everyone I ask. At about 170,000 miles I had some work done to help the performance which was pretty poor at the time. The EGR was blanked off and a full width Allisport intercooler fitted along with an electric Pacet fan plus a tweak to the IP. At the time I was pleased with the performance improvements.

Fast forward to about 2012 and it's had a full respray during which time the garage carrying out the work ended up reconnecting the Pacet fan with the wrong polarity so it blew air forward rather than drawing it into the engine bay. I didn't notice anything amiss at the time and, in the spirit of getting the Defender to drive more like a Disco while retaining the load carrying ability of a 110 I had my transfer box swapped out for a Discovery unit. At the time the garage (a different one) pointed out oil swirling around in the coolant header tank. The head was removed, two terminal cracks identified and a new head was needed. The head failure was likely down to an epic 14 hour journey through France at 38C where the gearstick got too hot to touch and the car was still pinging as it cooled for hours afterwards. I ordered a new head from Paddocks or Craddocks (forget which) that was listed as OEM. The head arrived and had all of its valves and studs swapped from the old to the new. During this process one of the injectors either snapped as it was being removed or was deemed by the garage as knackered and was replaced with a spare that was knocking about (I know no more about it than that). All reassembled I picked the Landy up again but it seemed slower, quite a bit slower. It's OK from a standstill but struggles to get above 65-70. Given the max design speed is 85 or so I would expect to be able to achieve that speed with the transfer box and intercooler mods that I have had.

I've looked at the air filter and even ran it for 5 miles with no filter to see if the filter was impeding airflow. I have also looked at the three rubber intercooler pipes for signs of delamination but they are fine.

So, my gut feeling is fuelling is the root of the issue but I'm loathe to spend £200 on new injectors or start frigging about with lift pumps if there are other steps i should take first.

Can anyone offer some sage advice?
Thanks,
Nerdos.

have they connected the fuel lines the correct way round?

I would have thought so. That's a work/not work arrangement rather than a lack of performance issue isn't it?

You would be suprised. We bought a a3 1.9 tdi with a rotor pump setup, all be it an electric one like the edc engines have. And they connected the pipes wrong when changine the tank sender. The results were strangled performance until i noticed what the garage had done and swapped them back over.

Nerdos said:

It has always had a fair bit of black smoke on acceleration - more than usual according to pretty much everyone I ask.

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This could be caused by many things. But likely someone fiddling with the injector pump before you owned it.

Nerdos said:

At about 170,000 miles I had some work done to help the performance which was pretty poor at the time. The EGR was blanked off and a full width Allisport intercooler fitted along with an electric Pacet fan plus a tweak to the IP. At the time I was pleased with the performance improvements.

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Who tuned the injector pump?

Nerdos said:

in the spirit of getting the Defender to drive more like a Disco

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I honestly don't really understand the want to do this. I know you said load carrying too, but what are you carrying? A Disco has almost as much room in it and able to carry the same weights.

But there several fundamental design differences which will always make a RRC/Disco far more refined and comfortable. And you'll never be able to address them on a Defender.

Nerdos said:

I had my transfer box swapped out for a Discovery unit.

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A word of note. A stock Discovery tyre is circa 28-29" tall. While a stock Defender tyre is more like 31-32" tall (ignoring the silly 205's...).

What this means is, that on the road a stock Defender will run about the same mph/1000rpm in top gear as a stock Disco does.

So if you retain the stock Defender tyres (235/85, 265/75 or 7.50's) and add the Disco transfer box, it will appear over geared and will reduce acceleration in-gear. I.e. make it feel more sluggish.

Nerdos said:

All reassembled I picked the Landy up again but it seemed slower, quite a bit slower. It's OK from a standstill but struggles to get above 65-70. Given the max design speed is 85 or so I would expect to be able to achieve that speed with the transfer box and intercooler mods that I have had.

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This really isn't easy to diagnose over the net.

But you need to supply specifics. Is this the first time you've driven it with this transfer box?

What size tyres are you running?

Did it still smoke a lot after you had the injector pump tuned? And does it still smoke now?

How does it feel through the gears? Does it want to rev, can you feel the turbo coming on boost?


Do you know if the speedo drive is correct? So when you say 65mph, what speed are you really doing (GPS?) and vs what it used to do?


Things that could cause poor performance.

Timed wrong.

Boost leak.

Fuelling issue.

Valve rocker adjustment.


To help diagnose this kind of thing, you may want to look at investing in a rev counter, boost gauge and EGT gauge. They are not overly expensive to add. But will help see what is happening.

Thanks for weighing in 300bhp/ton
To attempt to answer some of the points/questions you raise:

The IP was tuned/adjusted by Alldrive near Swadlincote. I believe that they simply followed the instructions that came with the intercooler from Allisport. I don't think it is a particularly precise process, more something like take top off pump, rotate thingy inside it by a few degrees to increase fuelling and then reassemble.

As for the Defender v Disco/RRC debate; I always wanted a Land Rover (and by that I mean Series or Defender shape) from before I could drive. I finally realised that ambition 12 years ago when I bought a 100" 'Defender' with 2 seats. When I got a family I chopped that in and got a 12 seat station wagon. As time went on I started to think that the Discovery would have been a more suitable vehicle for my needs but I wasn't likely to change as I had a) sunk so much money into the Defender that I wasn't keen on letting it go and b) I just prefer the way the Defender looks. As for load carrying - I was referring to volume rather than mass. We use the Defender mainly for camping and Mrs Nerdos does like to take a lot of stuff with us and I would maintain that a 110 with a full length roof rack can accommodate more stuff than a Disco 1 or 2 (which is what I would be able to afford). The Defender is here to stay, or at least until someone steals it. I had the transfer box swapped as I thought this would increase the gearing thus giving me lower engine speed for a given road speed. With a relatively unladen vehicle (in terms of weight) and with the larger intercooler and IP tweak I thought this set up would work and the engine would not labour. If I were in the habit of hauling loaded horse boxes through mountains I would not have taken this action. In summary, I accept that a Defender is not a Discovery and even that if I were starting again I may have bought a Disco but that won't stop me attempting to make the Defender a little quicker and more comfortable. To quote George Bernard Shaw “The reasonable man adapts himself to the world: the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.”...and that's me I guess.

The tyres are 265/75
I've had this transfer box in place for a couple of years but as it was fitted at almost the same time as the new head I never got to assess any changes it made in isolation from all the other changes.
I suspect that the original speedo overstated the road speed but I think that the combination of Disco transfer box and 265/75 tyres have made the speedo pretty much bang on and I say this as I have compared the speedo reading with those digital roadside signs that tell you your speed and then thank you for driving considerately. GPS tells the same story.

The turbo definitely kicks in but it seems to give less benefit than before the head was changed.

The engine seems happy to rev up to a point (so from a standstill and through the midrange) but is reluctant to achieve a top speed over 65. I tend to cruise at this speed anyway but cruise speed should not equal top speed in my book.

I will take your advice on the gauges. I believe the tacho is the tricky one on a Tdi. I notice that EGT gauges can be had from about £18 but then there seems to be a step change to around £120+. Will the cheaper stuff actually be good enough for this diagnosis?

And finally your list of things that could cause poor performance all look like they could fit my circumstances.
Rockers: could be. The engine sounded different through the air intake after it had the head fitted.
Fuelling issue: it had the injector fitted that was lying around when the original broke so the overall condition of that item is unknown.
Boost leak: maybe less likely as I have inspected all that I can and found it to be in OK shape but I won't dismiss it as a potential cause.
Timing: I have no idea about this at all.

So, next steps EGT and boost gauges plus rev counter if I can and I will then need to report back in the hope of some more help.

Thanks for your involvement to date.