Automatic 300TDI low on power but otherwise running fine. What to check?

Hi guys,

I've recently ended up with my dad's Land Rover Discovery 1 300tdi Automatic (so has EDC pump rather than manual pump). The vehicle starts first time with the smallest puff of smoke, idles fine, and doesn't have any check engine lights. When driving it's smooth, no smoke from the exhaust, and no issues other than it being very slow, even for an auto 300TDI. When he bought it at the end of 2019 I drove it home a few hundred KM's for him and found it quite acceptable on power even compared to my V8. It would happily run up to 80-85mph (130-140kmh) without too much struggle for overtaking and never felt like I was in danger of not having enough power at intersections to pull out. Now that I've taken over it as he's moved overseas it's intolerably slow. I'm talking 0-100kmh (0-62mph) in around 25 seconds with properly inflated tyres, and struggles to make it past 65-70mph (110-115kmh). I don't know when it lost its power, if it was sudden or gradual since I'm not the one who drove it the last year and half.

I'm going to dive into it this weekend hopefully to figure out what's going on and was hoping for some recommendations or things to check? This will be the first time I've ever worked on a diesel so please be kind I don't know all the terms!

Cheers,
James

Hi James, It's encouraging that it's running and starting well but it should be performing better than that. Start with the basics, renew your air and fuel filters first, then I would take a look at the fuel sedimenter and drain it if it is still in use and hasn't been bypassed, if you're still struggling for power after that I would renew your fuel lift pump but don't go for a cheap one, get a Delco pump, they are far better and they also have a filter that can be cleaned, I do mine regularly and it takes no more than two minutes. All of these are simple jobs that you should be okay with.

Don't forget to let us all know how you get on with it, even the most trivial bit of information can be useful to others in the future.

DiscoRay said:

Don't forget to let us all know how you get on with it, even the most trivial bit of information can be useful to others in the future.

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Yep I will! There’s nothing worse than searching a forum and finding someone who’s had the exact same issue and either never posted the fix or worse, just said “Sorted now”. I’ll make sure not to be that guy!

I’ve ordered a new lift pump, fuel filter, and air filter. Hoping that will sort me out but if not I don’t mind since it’s good to replace them anyway. Also picked up a new timing belt kit at the same time since I don’t know when it was last done. Fingers crossed it’s an easy fix!

Might be worth checking pump timing, slightly advanced makes starting easier, dont worry if you got to far as it just puts engine light on, so you then retard it a knatts tadger and away you go.

Might be worth asking if it has had any work done in your dads care?, as std they are painfully slow, and by slow I mean really slow, the fact you say say it went well makes me suspect maybe it had a plug in chip or something along the same lines? the throttle is basically an on/off switch, but chipped they are a proper flying machine.

Cheers! Will try the easier stuff first then investigate pump timing if I still have no luck. The only work not done by myself while it was in his care was some wheel bearings and an ABS sensor which were replaced. Although I can see that it has a catless downpipe and EGR deleted, so it looks like the previous owner did some work to make it a bit more lively. I understand they're quite slows as standard, but from what I've read 0-60mph in 25 seconds is slow even for an automatic 300TDI.

Iirc most chips either plugged into the large multiplug a few inches from the inj pump itself, some others plugged into the engine ecu which is behind the drivers side kick panel just above the throttle pedal.
The air flow meter is the old fashioned sliding metering type, Iirc some of the faults do not throw a code?
Have you checked all the intercooler hoses? again from memory the top one splits near the egr inlet?
Think theres a pressure/temp sensor on the inelt manifold somewhere, I am sure the intructions are on the web somewhere, with resistancte readings etc so you can check them.

I wonder how many 300 autos are left nowadays?

I have seen it said many times how painfully slow the autos are but I don't entirely agree, when mine was completely standard it would take a while to wake up and get off the line but once underway it's performance was acceptable, in fact it was a bit quicker than my manual 200tdi. I think that I have been quite lucky with mine as I know quite a lot of people have had problems with the EDC fuel pump but I have never had any trouble whatsoever with mine after eight years and seventy thousand miles and it really does run like a swiss watch, let's hope it carries on like that. I have made a few inexpensive changes to it recently and it is now quite lively, I can't be sure because I have never tried but I guess it would probably stay with a TD5 now.

DiscoRay said:

I have seen it said many times how painfully slow the autos are but I don't entirely agree, when mine was completely standard it would take a while to wake up and get off the line but once underway it's performance was acceptable, in fact it was a bit quicker than my manual 200tdi. I think that I have been quite lucky with mine as I know quite a lot of people have had problems with the EDC fuel pump but I have never had any trouble whatsoever with mine after eight years and seventy thousand miles and it really does run like a swiss watch, let's hope it carries on like that. I have made a few inexpensive changes to it recently and it is now quite lively, I can't be sure because I have never tried but I guess it would probably stay with a TD5 now.

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Tbh that aint hard as td5 are as flat as a well squashed turd as well

Interesting to read these comments, I was in my brother's manual Tdi Disco a few days ago, though performance was quite good. Like the op, I also think my auto Tdi (edc) is very slow but I've recently been driving my latest toy, a nice 2005 Td5 auto and I honestly think it's even slower. Some investigations due. I read somewhere of wiring in a resistor in some way to make the edc pump work better?

Give this a try.
https://www.ebay.co.uk/itm/233281970371?hash=item3650b060c3:g:HrIAAOSwq4Nersco
I've fitted one and it's transformed it.

Kenbo said:

Interesting to read these comments, I was in my brother's manual Tdi Disco a few days ago, though performance was quite good. Like the op, I also think my auto Tdi (edc) is very slow but I've recently been driving my latest toy, a nice 2005 Td5 auto and I honestly think it's even slower. Some investigations due. I read somewhere of wiring in a resistor in some way to make the edc pump work better?

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I test drove aTDd5 XS years ago with a view to buying it, my god that was slow, I was fascinated how you could floor ir and wait then wait some more for the explosive power delivery!
I think all discos up to D4 were underpowered, D4 is 245/255 bhp, more than twice the power of the tdi, and 110bhp up on the TD5.
Iirc TD5 auto you have to be careful as the box can only take so much power.