1.9D acceleration issues

[baldmosher]

Copied from "what did you do" thread and compiled from previous thoughts on the subject

Car has been struggling a bit with acceleration since I bought it (with 234K on the clock).

Main symptom is "flat spots" in acceleration. Also it is sluggish below turbo range, although a few people have mentioned that is the case with their 1.9D, and of course, it's common to have "turbo lag". My last 1.9D was much more torquey below turbo range but I did assume that's because it was chipped or retuned by the previous owner. When I floor it, this one picks up quicker from 1700rpm, as you expect, but acceleration then drops off markedly at 3200 in 3rd, 2700 in 4th, 2400 in 5th. It still picks up speed but lacks power. Oddly when cruising at higher revs the problem doesn't seem so obvious but it's definitely weaker than it should be.

Another trip down south this week, this time in VERY hot weather and crap traffic everywhere on the M4, A404 and M40, as I left at 4:30pm instead of 3:30pm.

Engine was really struggling with the heat, seemingly taking ages to chuck fuel in, the usual flat spots in the turbo range felt no worse than before, but sub-turbo it was horrible. Slightly improved once the engine cooled down a bit after cruising at speed, but still not great. Even in neutral it was struggling to pick up revs so it seemed to be a fuel or air issue.

Not much better today, it just doesn't want to pick up revs quickly at all, although seems a bit more "normal".

Possible causes so far:

- fuel pump (suggested by my local Volvo specialist)
- fuel injectors (suggested on the "what did" thread)
- fuel filter (unlikely, was changed at last service 8k before I purchased)

- MAF (I bought a MAF from Minty but still haven't found time to fit it)

- EGR cleanout (probably never been done)

- turbo vac pipe (local specialist checked turbo vac pipes and replaced one and said it's getting plenty of boost, which points to fuelling or sensor issues)

- dirty electronic connections in engine plugs/wiring

Local specialist found no error codes (wouldn't a faulty MAF crop up?) and reckons it's "just an old engine" which seems like a cop-out to me.

I have a couple of different "chip tuning" boxes ready to go on but I don't think that's the problem anyway.

I'll keep this updated as I rule things out. If you've got any other suggestions let me know!

[skyship007]

Are you getting any smoke, using engine oil or coolant ??

Have you tried unplugging the MAF sensor to see what happens ??

It does sound a bit like a blocked EGR or a leak from a turbo hose. A faulty MAF should show up as an error code.
It's worth trying a direct feed injection cleaner like Liqui Moly Diesel Purge before pulling the injectors, although if it's not smoking at idle or when booted, I doubt if they are causing the problem.

[gatos]

Dirty MAF, dirty EGR, split vacuum hoses or my magic cure for everything: dodgy N75 TBC N75 solenoid. Easy to check the solenoid. Just unplug the small hose that goes from the right (facing the engine from the front) of the solenoid to the air intake hose and see if there is any vacuum. If not, then the N75 solenoid is faulty

[bobthecabbage]

Mine is also very flat at low down revs and stalls easily if you have the air con on (blower is usually flat out and radiator fan kicks in when stationary so a lot of electrical load too).
It picks up better from 1700 ish with the air con on which is presumably because the engine is getting/burning more fuel due to the load of the air con pump and fans.

Does it have an intercooler? If so can you see if its clear of any obstruction? Obviously air has to blow through it both on the inside and the outside to work properly.

234k is quite a high miler really, mine only has 136k on it!

[ijmorrison]

It might be relevant (or not) but I had mine stalling under load, flat spots, etc ...small leak in the diesel pipes near the tank ...if it can leak out air can get in

Might be worth a quick check .. mine is running better after getting it back today

Iain

ps Goes on the corner ...

[bobsleigh]

Im getting lots of lag below 1800RPM since I cleaned my EGR... Am going to try cleaning the MAF and making sure I have no Turbo leaks, however I think its different to yours as mine will pull cleanly to the redline even in 5th gear.

My solution is to maybe get a tuning box as I have a feeling its the way these engines are.

If I have any luck this weekend ill let you know.

[skyship007]

Originally Posted by bobsleigh

Im getting lots of lag below 1800RPM since I cleaned my EGR... Am going to try cleaning the MAF and making sure I have no Turbo leaks, however I think its different to yours as mine will pull cleanly to the redline even in 5th gear.

My solution is to maybe get a tuning box as I have a feeling its the way these engines are.

If I have any luck this weekend ill let you know.

If you have got a lot of lag it makes sense to fix the problem before playing around with a tuning box, otherwise you might make it worse not better.

[kieran40]

Mine was behaving funny and it was a dutty maf all is well now and yea was doing it in the heat aswell

[gordonr]

got a little flat spot around 2500 but seems to pull again
not too concerned as there is no smoke , not going through oil or water either

[Cornishv40]

I have no acceleration issues in my T4.. lol