Intermittent engine power

Rapido925M

Rapido925M

Joined
Feb 5, 2014
Posts
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Location
mid-Norfolk
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29,980
MH
A class
Exp
since 2006
For some time I have felt that the turbo hasn't been working all of the time, causing me to change down on the slightest incline and having no power when trying to accelerate. a couple of weeks ago I took it to my local trusty garage who found a loose clip on an intercooler, which they tightened. Following a smoke test and a test drive they proclaimed it satisfactory.

When I collected it I wasn't particularly impressed but I wondered if I was imagining what it used to be like. However, other things got in the way and it was only today that I managed a decent run. It barely accelerated up a slip road on to a dual carriageway and I could only just get up to 60mph going down a gentle slope. I called in at the garage and they have suggested fitting a new fuel filter: this one has done 10k miles in 4y.

As I left the garage the engine roared and pulled like an express train: it climbed that gentle slope at 62mph and kept accelerating happily. All the way home it felt like my old van.

My son has suggested it's my fault for using cheap diesel and I should let the tank run almost empty then fill with "decent" fuel (plus some Redex).

Any thoughts please?

TIA - Gordon

The garage is looking to source a new filter and find time to fit it before I head to the Lake District on 1 March.
 
Rapido925M said:
My son has suggested it's my fault for using cheap diesel and I should let the tank run almost empty then fill with "decent" fuel (plus some Redex)
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Don’t want to get the popcorn out but cheap diesel itself would not be the cause of the issue. Many threads about the subject both here and on FB. However the occasional fill with a fuel like V Power does no harm at all.
 
Rapido925M said:
I called in at the garage and they have suggested fitting a new fuel filter: this one has done 10k miles in 4y.

As I left the garage the engine roared and pulled like an express train: it climbed that gentle slope at 62mph and kept accelerating
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:unsure: As with Figaro 's comment.............so how come it now pulls like a train?

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Rapido925M said:
For some time I have felt that the turbo hasn't been working all of the time, causing me to change down on the slightest incline and having no power when trying to accelerate. a couple of weeks ago I took it to my local trusty garage who found a loose clip on an intercooler, which they tightened. Following a smoke test and a test drive they proclaimed it satisfactory.

When I collected it I wasn't particularly impressed but I wondered if I was imagining what it used to be like. However, other things got in the way and it was only today that I managed a decent run. It barely accelerated up a slip road on to a dual carriageway and I could only just get up to 60mph going down a gentle slope. I called in at the garage and they have suggested fitting a new fuel filter: this one has done 10k miles in 4y.

As I left the garage the engine roared and pulled like an express train: it climbed that gentle slope at 62mph and kept accelerating happily. All the way home it felt like my old van.

My son has suggested it's my fault for using cheap diesel and I should let the tank run almost empty then fill with "decent" fuel (plus some Redex).

Any thoughts please?

TIA - Gordon

The garage is looking to source a new filter and find time to fit it before I head to the Lake District on 1 March.
Click to expand...
Do what your son says……….you should know by now that kids know everything:ROFLMAO::LOL:;)
 
rod_vw said:
Air Mass Sensor failed or failing?

Very unlikely to be the diesel that you have been using, I've been using supermarket diesel both in the UK and Europe for over thirty years without any problem.
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The science behind fuels backs you up
 
rod_vw said:
Air Mass Sensor failed or failing?

Very unlikely to be the diesel that you have been using, I've been using supermarket diesel both in the UK and Europe for over thirty years without any problem.
Click to expand...
Odds on favourite!! Classic signs👍👍
DJT
 
If your van has a Mercedes engine then what you experienced has been well reported in Sprinter forums, if it struggles on inclines change the fuel filter is the first thing to try.

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Figaro said:
So the suggestion of a new fuel filter fixed it ?
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No! I stopped at the garage to discuss the problem: the fuel filter will come later.

I don’t know what caused the improvement and I’m wondering if fuel filter problems are consistent with this behaviour.

Gordon
 
Rapido925M said:
No! I stopped at the garage to discuss the problem: the fuel filter will come later.

I don’t know what caused the improvement and I’m wondering if fuel filter problems are consistent with this behaviour.

Gordon
Click to expand...
If the filter was blocked to the point of fuel starvation I guess that would result in reduced power.
Definitely worth changing the filter, but it's odd it started performing correctly without doing anything ?
Probably advisable to replace the air filter too
 
Rapido925M said:
No! I stopped at the garage to discuss the problem: the fuel filter will come later.

I don’t know what caused the improvement and I’m wondering if fuel filter problems are consistent with this behaviour.

Gordon
Click to expand...
Two possibilities for losing power inconsistently are debris in the fuel tank around the pick up pipe and a blocked tank breather as either will reduce the fuel flow. Both of these usually solve themselves when the engine is stopped. The former would be more likely with the symptoms you describe.
 
Derbyshire wanderer said:
Two possibilities for losing power inconsistently are debris in the fuel tank around the pick up pipe and a blocked tank breather as either will reduce the fuel flow. Both of these usually solve themselves when the engine is stopped. The former would be more likely with the symptoms you describe.
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The fuel tank is currently full (don't know if that is relevant). Presumably the only way to clear debris (its a 2002 vehicle!) would be to empty the tank?

If debris is the problem, then the filter should stop them getting to the injectors. Could debris in the filter sometimes allow full flow but sometimes prevent it? TBH, previous problems often cleared if I switched off the engine, originally for long periods but increasingly becoming shorter periods of decent power.

To me it is definitely sounding like changing the fuel filter should improve the situation: just hoping that they can do it before I need to go to the Lakes.

Thanks for all the comments.

Gordon
 
What engine have you got and did the garage find any fault codes in the EMU, I'll presume not as you should have had a "check engine" warning on the dash.

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If it's only done so little mileage, it probably hasn't been serviced SO, get it serviced, with new filters (check nothing been nesting in the air filter) fill it up with good diesel (do not wait until it's empty as you will be sucking up sludge) and, once warm, give it some revs for a while.
Have a good holiday! 👍
 
Italian tune-up? Once a trip I give ours around 20 minutes at around 3000rpm, or sometimes a long slog in lower gear up a hill does the trick. The idea is to get the emission systems heated up to do what they are supposed to do which is to burn off the crud. Unfortunately most m/hs only pootle along, unlike their commercial brothers, which can quickly bung everything up. From what you say it sounds likely to me.

Years ago my mother had a Mini Cooper which only got used to take her to school (1 mile!) and the weekly shop. Once a month I used to take it out and give it a thrashing and she always commented it went much better after.
 
It’s the 2.7l, 156 bhp, 5-cylinder engine (2002) Mercedes. I’ve had it almost 18y and it’s given little problem.

Until COVID we typically did 5k miles pa but we were just about to get back on the road when two terminal brain cancers plus hospitalisation for 94y old hit close family members and we provided intensive support almost daily. Even this trip to the Lakes is to enable our daughter to collect her new camper rather than enjoyment for us.

So keeping the van in good condition has taken a back seat, hence why its only done 10k in 4y and hasn’t been serviced since 2020.

Gordon
 
Rapido925M said:
It’s the 2.7l, 156 bhp, 5-cylinder engine (2002) Mercedes. I’ve had it almost 18y and it’s given little problem.

Until COVID we typically did 5k miles pa but we were just about to get back on the road when two terminal brain cancers plus hospitalisation for 94y old hit close family members and we provided intensive support almost daily. Even this trip to the Lakes is to enable our daughter to collect her new camper rather than enjoyment for us.

So keeping the van in good condition has taken a back seat, hence why its only done 10k in 4y and hasn’t been serviced since 2020.

Gordon
Click to expand...

If it's 2002 I presume it doesn't have egr valve, dpf or even variable vane turbo which will make fault finding a lot easier.

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Rapido925M said:
The fuel tank is currently full (don't know if that is relevant). Presumably the only way to clear debris (its a 2002 vehicle!) would be to empty the tank?

If debris is the problem, then the filter should stop them getting to the injectors. Could debris in the filter sometimes allow full flow but sometimes prevent it? TBH, previous problems often cleared if I switched off the engine, originally for long periods but increasingly becoming shorter periods of decent power.

To me it is definitely sounding like changing the fuel filter should improve the situation: just hoping that they can do it before I need to go to the Lakes.

Thanks for all the comments.

Gordon
Click to expand...
Yes the filter will stop debris getting to the injectors but I am thinking something that is getting around the pick up pipe.
I have seen before that the internal paint comes off old Jerry cans and floats around the fuel tank until the suction of the fuel pump manages to get it wedged across the end of the pick up line and restricts flow. Switch off the engine, suction drops and it falls away.
It will need inspection to confirm and then a good clean if anything is seen.
Edit to say that your comments about standing for sometime could also indicate diesel bug as it can do exactly this
 
Derbyshire wanderer said:
Yes the filter will stop debris getting to the injectors but I am thinking something that is getting around the pick up pipe.
I have seen before that the internal paint comes off old Jerry cans and floats around the fuel tank until the suction of the fuel pump manages to get it wedged across the end of the pick up line and restricts flow. Switch off the engine, suction drops and it falls away.
It will need inspection to confirm and then a good clean if anything is seen.
Edit to say that your comments about standing for sometime could also indicate diesel bug as it can do exactly this
Click to expand...
I can picture exactly what you are saying. I’m not sure how it would be solved: some sort of vacuum pipe inserted through the filler?

Being aware of diesel bug I do tend to store it with a full tank

Thanks for the advice

Gordon
 
Rapido925M said:
I can picture exactly what you are saying. I’m not sure how it would be solved: some sort of vacuum pipe inserted through the filler?

Being aware of diesel bug I do tend to store it with a full tank

Thanks for the advice

Gordon
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A vacuum won’t work.
If it is the problem then running the fuel low prior to removing the sender unit is the best option as you can get an arm in the tank to clean it properly. Horrible job but at 22 years old it could well be ready for a spring cleaning.
 
Just smiffy said:
As TerryL said the Italian tune-up is the most effective and cheapest…

Every third fill up I give it a good blast to the fuel station, you don’t have to go fast, just keep it in a low gear and keep the revs up BUT ONLY once the van is up to normal temperature…
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I’ve been doing that for years: hammering along the motorway for 10-20 miles at high speed, especially on the continent 😉

However, apart from on the way home yesterday I haven’t been able to get above 60 for a few months: presumably because of the leaking intercooler pipe. (I haven’t been out in it very much since September when it did 200 miles up to Teesside: chugging rather than roaring ☹️).

Sadly, cheap solutions seem unlikely at the moment 😉

Gordon
 
For info I just cured a misfire problem on Rio petrol toad with STP fuel additive.

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That was my comment to the garage secretary when I booked it in last month. She phoned Mercedes who said that it’s part of the turbo and can’t be replaced separately.

Gordon
 
Have you ever had a boast control valve replaced I had a 962M with the 2.7 156hp 5 cylinder engine and had to replace this valve a couple of times in fact I have a brand new Mercedes boast control valve in the garage as I changed the motorhome to a Fiat one .
it is located on the off side below the air filter
.
 
Rapido925M said:
That was my comment to the garage secretary when I booked it in last month. She phoned Mercedes who said that it’s part of the turbo and can’t be replaced separately.

Gordon
Click to expand...
The wastegate valve is part of the turbo but it's often just a case of disconnecting the actuator and manually opening and closing the valve a few times using the actuation lever. This can clear away any rusty or sooty deposits that may be preventing the wastegate valve from operating properly.
Also as above, check the boost control valve and vacuum pipes connected to it first

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