diesel, poor acceleration, worse than expected!!

Hey guys, I have just lost my mind and bought a 99 p38 Diesel auto. done 108k, and checked in relatively good order, It came to me with a sick key! which has now been sorted as has the sticky ignition barrel, so after a refurb it now locks and unlocks and starts first time, go me!! Next problem is!! lack of acceleration, I select drive and move off, but even if I floor the throttle it just builds revs slowly and speed even slower, the gears change up and down without problem, sport mode selects and deselects no problem, I have tried to select lo range and back to see if it was a switch in the auto box, but makes no difference. all works fine and you hear and feel the relevant clunks underneath. It is scarey at junctions and up hills as the car will just pull slowly and barely accelerate, eventually the revs will build and the gears will go up. It was like this when I bought it, but I just put it down to me being a bit light on the throttle on test drive. On driving it home, it was slow for a good while but then after a blast on the motorway, it suddenly seemed to spring to life and find a new lease of life, so I thought all was well, but then after that I have had key problems and imobiliser problems and had to reset it all countless times and even disconnect the battery, I was wondering was this the cause and I need to take it a long run again? All hoses are in good order, she starts first time every time, (now after key fix) very little smoke, a tad noisy on idle but nothing bad. no leaks all levels good, will no signs of internal damage. It may have a power box fitted, not sure yet, have to investigate, there is a strange looking blue box, on the RHS inner wing as you look in the engine bay, just in front of what I think is the MAP (on board just clear of bulkhead) not connected to MAP but I think it has a lead going towards inlet area.

Have you checked the little pipe going to the MAP sensor as this can split or gum up causing lack of power....

Also check the turbo hoses for blockage/collapsing/delaminations....

If yours has the EGR ('99 onwards) if the EGR is sticking this can cause lack of power in the lower rev range....whip it off and give it a clean...along with the intercooler too as these can gum up also.....

The Diesel does have a weird accelerator profile and they do need a prod to get going, but with a hefty boot they should sit up and take off even from a standing start.....

yep with Saint on this one.

does it kick down and rev up ?

The thing near the bulkhead is the EGR modulator valve. MAP sensor is bolted to top of fuel filter. Check that the pipe to it from under manifold is not split or blocked that feed to it is clear and Map sensor is clear of oil. Intercooler may need flushing. Intercooler pipes need checking for internal delamination. Could have partially blocked Cat. Or very dirty air cleaner. Duff power box. You need to check all of these things could be one or a combination of them.

it's natural!!

If it has a power box which intercepts the loom the the FIP it could be that it's faulty. If it has a MAF sensor, it could also be that as if it fails it reverts to fixed fueling maps. diagnostics needed to check though. You could try unplugging it to see if it makes a difference.

Datatek said:

If it has a power box which intercepts the loom the the FIP it could be that it's faulty. If it has a MAF sensor, it could also be that as if it fails it reverts to fixed fueling maps. diagnostics needed to check though. You could try unplugging it to see if it makes a difference.

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Glad you mentioned that Keith. If the MAF is faulty it could be causing the EGR to open on acceleration which should not happen. That would certainly cause the problem.

change the diesel filter

Great long list guys thanks, its defo in the lower rev range that is having issues, I have taken it a long run, and its still a pain, the intercooler hoses feel quite soft, going to check the EGR now, and the blue box infront of it.

I had a similar issue cured by changing the diff oil. It was like tar so would really slowly pull away from junctions. A hill start was almost impossible. Could be worth popping out the diff fill plug and check the quality of the oil.

It doesn't fall under a normal server to change the diff oil so rarely gets done.

They are no McLaren F1 in terms of acceleration, but if you bury the throttle in the carpet they should take off. Although speaking of carpet, do you have aftermarket floormats? The floormats that came with my P38 were not made for it so had a tendency to get wedged under the throttle pedal stopping you from getting WOT. I cut a slot out of them so the pedal can touch the floor now.

cheers bix, think dropping the oil is going to be the ticket, weekend job I think.!!!

Also check auto box oil level.

nathanstev said:

Great long list guys thanks, its defo in the lower rev range that is having issues, I have taken it a long run, and its still a pain, the intercooler hoses feel quite soft, going to check the EGR now, and the blue box infront of it.

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No power below 2500 rpm is normal

Also with due respect to others i seriously doubt that EP120 or even EP 140 would make a great deal of very noticeable difference to the acceleration.

Is it a 2.5L D? If so that's what they drive like in my experience....... like a stunned slug! I had a mate's in the alps and i could have got out adn run up the hill faster!

Not like my L322 TD6, which is like a rocket ship! .... (wait 2 secs for Data to get back ...)

:smokin:

dolphinboy said:

Is it a 2.5L D? If so that's what they drive like in my experience....... like a stunned slug! I had a mate's in the alps and i could have got out adn run up the hill faster!

Not like my L322 TD6, which is like a rocket ship! .... (wait 2 secs for Data to get back ...)

:smokin:

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Mind over matter or image over substance

dolphinboy said:

Not like my L322 TD6, which is like a rocket ship!

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Really?
The 0-62 for the 2.5 is 14.7 seconds.
The 0-62 for the 3.0 is 13.6 seconds.

Just over a second faster is not exactly rocket ship status.

Bix said:

Really?
The 0-62 for the 2.5 is 14.7 seconds.
The 0-62 for the 3.0 is 13.6 seconds.

Just over a second faster is not exactly rocket ship status.

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Think i would back my 2.5 as being quicker than either of those.

Bix said:

Really?
The 0-62 for the 2.5 is 14.7 seconds.
The 0-62 for the 3.0 is 13.6 seconds.

Just over a second faster is not exactly rocket ship status.

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As I said, it's the placebo effect, mind over matter:lol::lol:

Datatek said:

As I said, it's the placebo effect, mind over matter:lol::lol:

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But the 3 litre does allow you to run into things that bit sooner.