Flat spot at 40mph?

[Muffatt]

I have a '95 2.5 4WD

On the whole she drives very nicely, smooth gear changes and good acceleration but there's a flat spot/loss of power at 40mph?

It's a pain in the arse if I am driving in a 40 zone as I either have to keep her at about 35 or just over 40, not ideal if there are speed cameras!

I have to almost floor it to get past this flat spot and if I'm going up a hill and trying to accelerate I feel like the bottom going to fall out! lol

I know she's too old to have an ECU, so any ideas on how I can resolve this, is it possible to do any sort of tuning on a Diesel engine or is something else causing this?

Thanks

[mikeonb4c]

I have a '95 2.5 4WD

On the whole she drives very nicely, smooth gear changes and good acceleration but there's a flat spot/loss of power at 40mph?

It's a pain in the arse if I am driving in a 40 zone as I either have to keep her at about 35 or just over 40, not ideal if there are speed cameras!

I have to almost floor it to get past this flat spot and if I'm going up a hill and trying to accelerate I feel like the bottom going to fall out! lol

I know she's too old to have an ECU, so any ideas on how I can resolve this, is it possible to do any sort of tuning on a Diesel engine or is something else causing this?

Thanks

Is this a definite change in behaviour from the way she used to drive? Could you work around the problem for now by using the S position on the gear selector while driving in town? Possibly the throttle position sensor is playing up (have a search for TPS on old posts on here). The diesel Bongo is relatively flat at 40 mph in top gear because the turbo has not really got into its stride I think.

[teenmal]

As has been said it could be a few things causing this problem, but the first thing I would do is start with the basic and change/clean the filters.

[mikeonb4c]

As has been said it could be a few things causing this problem, but the first thing I would do is start with the basic and change/clean the filters.

yup spot on, I totally forgot to consider the obvious. Filters first if there is an uncertainty over when last done. Do a search also for banjo filter and read up on that.

[Tony x]

Check your tire size.
When we changed tires from ones that had the same diameter as the originals (225 / 50 R17) to slightly larger ones (225 / 55 R17) we noticed that, when the Bongo changed into top at 40 mph, acceleration would back of noticeably. We either live with this or apply a bit more accelerator so it doesn't change up until about 45 mph.
Blanking off your egr pipe, if not done already is a good way to improve mid range power and will help you with your issue.

[Northern Bongolow]

on the top of the diesel pump is a pipe about 10mm dia, it goes forward to a connection on the inlet manifold, is this pipe connected, if it is, under where the pipe fits to the top of the pump is a diaphragm, this can fill up with oil and make the pump slow to respond to revving, a quick clean out is usually all that is needed.

[Muffatt]

Thanks for all the replies.

She's been doing this for a long time now but it seems to have got worse more recently?

The tyres are standard size so that's dveinitely not the problem.

Will try and check all th filters over the weekend and then take it from there.