Gutless

I have a 1995 M reg 2.5 300 tdi disco and the only mods are a "decat" (removerd particulate filter) and an egr blanking plate. Initial pull away is pitiful but on the move dont seem too bad (Still not great) I know its a landy and not a sports car but early this morning I was on an empty M1 and found that on level ground in 5th flat out she does 75mph. I know this is already above the stated speed limit but it is suposed to go about 20mph faster than it currently does which shows there is a problem. Sedimentor has been emptied and cleaned and a new fuel filter and air filter has been fitted. The Landy doesn't have any black smoke at all on start up or when running flat out and only gives a little puff when changing up under heavy acceleration which makes me think its under fueled. Could it be the lift pump to blame or would that effect it in a different way? You can here the turbo spin up and feel the difference in power at about 2750rpm but still feels very weak... never driven another tdi to compare it to as I have only ever had a 3.5 twin carb which went like a rocket.

Disco Inferno said:

I have a 1995 M reg 2.5 300 tdi discoon level ground in 5th flat out she does 75mph.

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What revs are you getting to? 70 in top in mine (31" tyres thobut) is 2800 rpm and it spins up on the flat to 3750/4250 ish, depending on the wind and an indicated 90/95+

If it's getting 4250+ then your gearing is low, maybe there are different size tyres on, or lower geared diffs?

You can here the turbo spin up and feel the difference in power at about 2750rpm but still feels very weak.

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Hmm, my '96/97 300 Tdi turbo starts to spin up nicely at about 750 rpm less, anywhere above 2000 rom and it's going ...

All that said I'd have a look first at the air filter and air intake, then at the plenum chamber, egr valve and intercooler and it's piping. Look for a lot of really awful black sludge build-up. It could also be the pipes are 'floppy' and collapsing under turbo load, and therefore strangling the air intake.

How is the exhaust smoke situation?

Its on 235/70/16 tyres which I fitted and it was bought from a 65+ year old woman that had it from 2 years old so I doubt the gearing has been changed or the diffs have been changed but good thought. If it had been geared down I would expect the acceleration to be a bit more sprightly with a loss of top speed but it accelerates very slowly and has a low top speed. No white smoke from exhaust at all ever and only a puff of black when changing up under heavy acceleration but at no other time even under full load whilst towing. at 70mph with an incline it slow the Landy down too and thats driving solo with just me in the car with accelerater pushed to the floor. GPS confirms the speed to be there or there about. Revs in top gear I beleive were around 3000-3250 ish but to be fair I didn't check it accuratly. I'll give her another run tonight and get an accurate reading.

Disco Inferno said:

it was bought from a 65+ year old woman that had it from 2 years old so I doubt the gearing has been changed or the diffs have been changed. GPS confirms the speed to be there or there about. Revs in top gear I beleive were around 3000-3250 ish but to be fair I didn't check it accuratly.

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No worries, that's close enough to know it's not stupidly over or under geared and about right revs for the speed, but it should be able to go faster, which further says, to me anyway, that the breathing is wrong., so the bits I said earlier need checking. As there's little to no smoke I doubt it's a fuelling problem, unless it's just not getting enough, but I wouldn't touch the fuel pump or anything until you've got it running 'normally' first.

Does it rev fully when stood? Sit in drivers seat and apply throttle, see what revs it gets to flat out. If it's 4000 or less then maybe it's just slack in the throttle cable ... Open the bonnet and rev it by hand, see if it revs higher.

I will take it some where deserted and try the reving with and without the accelerator in a bit and let you know whats happening. With the no smoke I thought that maby not enough diesel was getting to where it was supposed to there for assuming possible fuel lift fault but I will rev the tits off it first and let you know the results.

Presumably it has a rev limiter or govnor fitted that will stop it from going neuclear when im holding the accelerator down?

Disco Inferno said:

Presumably it has a rev limiter or govnor fitted that will stop it from going neuclear when im holding the accelerator down?

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LOL, mine has ... Don't hold it down too long, it should get to full speed in a couple of seconds. MOT stations do this for much longer ...

are you sure that the injectors are ok?
the turbo should 'kick in ' @1800 with a noticable change in speed

Wish my power increase came in at 1800rpm!!! Its nearly 1000 rpm later than that. Dont know how to check the injectors though. Im not that diesely to be honest. I have always had large petrol engines so Im starting all over again now I have a diesel. could the injectors cause that 1000rpm delay in the turbo kicking in or could it just be a very low set boost presure?

If you've checked all the obvious things mentioned, boost pipes, filters, throttle cable... with the turbo not coming in till you say it could be that actuator is knackered causing the boost to be low. Grab the actuator rod with a pair of molegrips it's conneccted to the turbo under the exhaust manifold. Pull the rod towards the front of the car... it shoudnl't be easy to move (it's spring loaded) if there's excessive slack it's probably knackered. If an old ladys had it the wastegate might never have been open fully

Yours sounds exactly like mine was before I put veggie oil in.Started with 50/50 mix but starting was a bit reluctant so made it 75/ 25 diesel to oil.Check the fuel pick up pipes under boot floor they rust and air can enter .Also I have complete new exhaust.Mine was real slow before.Still get slight delay from standing start but I think they all do that.Really pleased with how it goes now .Had it up to eighty but then bottled out.

Reet now then its not the accelerator cable. Neutral foot to floor about 5500rpm then under the bonnet putted the linkage and only 5000rpm so it shows i'm a wimp and I should stick to using the accelerator . I'll have a tug on the actuator arm tommorow to see if its stuck. Did another 75mph run and reves were just over 3250rpm. Did a foot to floor in gear and power didn't kick in till just over 2500rpm. Its a pig round town with the start stop traffic and the impatiant buggers who beep you if you dont start rolling the split second the light goes green. keep chucking them ideas my way and I'm sure we will get there in the end. If its the injectors Pads sell Bosch err3339 injectors with vat about £175 for four so I'll go for the cheep stuff first

Danny... I have run it on rape seed mixes before with no change in performance and have changed the full exhaust system using a defender 90 down pipe to remove the discos particulate filter "cat" and a new middle and back section. Now running on 100% doisel cos the savings on oil aint realy worth messing with now the price has droped from £1.40 per litre

The fuel pick up pipes under removable plate in boot floor always rust. I cleaned mine up and then just encased them in loads of clear silicone.What are you getting to a full tank? Im getting about 500 and mines an auto.

Sounds a bit daft, but you have checked the handbrake, and other brake pads, are free running?

Also the wheel bearings. Feel the drive flanges to see if they are warm or hot after a run ... if they're hot it could be that the wheel bearings are too tight or not bearings any more .. While it's stood, lift a single wheel at a time and turn it by hand and se if any of them are harder to turn than any other.

If the engine can rev freely and all pipes and stuff are reasonable condition then it's possible to be drag in the drive train somewhere.

Once all that's eliminated then it might be worth checking the fuel pump etc ...

Although the barings arn't making any nasty grindy noises I will check that the wheels turn freely. I am 99% sure that the brakes are not binding cos it doesn't smell like its going to catch fire. When I replaced the boot floor the plastic circle with the pipes coming out (pick up pipes?) around the metal fuel pipes was a little split but if this was letting air in wouldn't it just miss and run like a reet bag a poo?

OK, so we've eliminated 'simple' stuff ... that's me out of ideas ...

Not really. next I'd check fuel filter, fuel lift pump and fuel pipes aren't blocked and all allow a good flow of fuel. As you've shown it can get up to revs when stood and can't when under load it has to be fuelling then, and possibly a bit costly in either parts or time to fix.

I'd also consider taking it to a local garage and have them check the injector timing and injectors. (Mainly 'cos I dunno how to do it myself and cba to read up on it until I need to)

Does the lift pump come apart or is it an unbolt it and replace it part? When I changed the fuel filter it still drove the same as it does now but for what they cost I could change it again.

To change

1) Fuel filter £2
2) Lift pump £22
3) Intercooler hoses £20
4) Pick up pipe thing on top of fuel tank £50
failing that
5) 4x Injectors £175

£269 if I fit all the bits myself and then theres the garage seting the injection pump up correctly.

The Landy is still quite hot from using it but I managed to get my finger round the actuator arm and couldn't budge it. I didn't swing off it but gave it a firm pull. How much resistance should it have or does it sound stuck? When its cool tommorow morning I'm thinking of wraping some wire round it and pulling on that as space is limited.

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Disco Inferno said:

1) Fuel filter £2
2) Lift pump £22
3) Intercooler hoses £20
4) Pick up pipe thing on top of fuel tank £50
failing that
5) 4x Injectors £175
£269 if I fit all the bits myself and then theres the garage seting the injection pump up correctly.

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I wouldn't buy anything yet. Have you taken the turbo inlet and intercooler hoses off and checked how clean/clogged they might be? and the plenum chamber, which would possibly mean a manifold gasket change too. It's also possible that the intercooler itself is clogged, so it would be wrth checking that too.

Then when it's all clean, if it isn't already, get a garage, Local Independant LR preferably, to check the timing of the injector pump.

Then I'd start with the bits you listed, in that order too, but do one thing at a time, you never know.