Thread: 300tdi performance ups and downs

Originally Posted by malsgoing130

Good morning all,
I think i have a problem with the performance of my 300tdi............Its not blowing too much smoke either, only noticable at night with other cars headlights but does seem to be produce too much smoke then .........

Please help, im very confused by the symptoms
Regards
Mal

I have noticed that the amount of smoke you apparently see in the rear vision mirror at night is, in itself, not a good indication of excess smoke / overfuelling

My 300Tdi does the same smoke stuff as yours at night etc, so I wouldn't worry about that.

Check out the hoses/clamps to and from the turbo/intercooler etc to see if they have any leaks.

The injector pump/engine that was replaced might be from an inport car that had the Electronic Diesel Control (EDC), that would explain the harness from the pump.

So maybe it has been setup to run mechanical pump control and not electronic, thus causing weird problems....I don't know.

The hunting up and down might be caused by a low idle speed.
I know mine doesn't like to idle smooth below 750rpm (hunts up and down), but just a tad over 750rpm and it is smooth 99% of the time, 760rpm smooth idle 100%.

At this sort of age, it's starting to get more & more common that the fueling mechanism at the top of the pump starts to seize up. (This is the mechanism which compensates for the extra turbo boost by adding extra fuel.) It's a simple mechanical jobbie, where a feed from the turbo comes in at the top and the additional pressure moves the mechanism.

Checking it out is simple:

• Pop off the throttle linkages (mark up where everything goes).
• Undo the 4x retaining screws.
• Remove the 'lid'.

Initially, you'll see a diaphragm, check the condition of this. Then, push it down and make sure it's moving freely.

If there's any rust in the area, you might want to give it a quick squirt of WD40, or something just to lube it up again.

NOTE - The position of the diaphragm and the concentric cone underneath is very important. If you remove, take note of its position.

HTH

M

All the pipe work is in good nick and tight I checked that, the idle spped on mine seems very low, where is the ajustment? and i think you are right about the pump being imported as there is no mention of this harness on Rave.
Thanks
Mal

Factory idle is actually 720+/-20rpm I think.

I've heard that some Tdi's can idle smooth at 600rpm (never seen one though) and others not 'til 800rpm.

On the drivers side in front of the injector pump there is a metal lever "thingy" that the throttle cable and kickdown cables attach to.
I think there is a nut and bolt arrangment there also, that you screw in, to move the position of the throttle lever so that it revs a bit higher.

You will also probably have to adjust the throttle and kickdown cables slightly though, if you change the position of the lever "thingy" they attach to.

Hope this ok? I aint no mech!

Originally Posted by camel_landy

At this sort of age, it's starting to get more & more common that the fueling mechanism at the top of the pump starts to seize up. (This is the mechanism which compensates for the extra turbo boost by adding extra fuel.) It's a simple mechanical jobbie, where a feed from the turbo comes in at the top and the additional pressure moves the mechanism.

Checking it out is simple:

• Pop off the throttle linkages (mark up where everything goes).
• Undo the 4x retaining screws.
• Remove the 'lid'.

Initially, you'll see a diaphragm, check the condition of this. Then, push it down and make sure it's moving freely.

If there's any rust in the area, you might want to give it a quick squirt of WD40, or something just to lube it up again.

NOTE - The position of the diaphragm and the concentric cone underneath is very important. If you remove, take note of its position.

HTH

M

Thanks, for the reply, I think the pump is newish would the above still apply? could the turbo have something to do with it?
thanks
Mal

Are the hose from the intercooler to turbo Rubber ? I was amazed the amount of stretch in mine when i revved it. Changed to silicon pipes and the increase in performance was noticeable. The rubber ones may be RS and causing a problem.

Hmmm... If the pump is newish then it's probably OK.

Try the air hoses on the -ve pressure side of the system as they can de-laminate and constrict the air flow.

M