Severely underpowered DCi

[Bob0907]

Hi all, I have a 2003 clio dci 65 which has a serious lack of power just now. It struggles to do 60 on the flat and when it hits a hill at full throttle in 4th or 5th it will just die down to about 50. Went to overtake an artic lorry on a crawler lane the other day and it ended up pulling away from me!

I have:
Replaced the turbo actuator and the wastegate is free to move
Checked the timing which is the same as it was when the cambelt was changed and the car drove fine
The turbo spins freely, there is slight play up and down on the turbo wheel, but im unsure if its enough to fail it?
I have cleaned the EGR valve
The fuel filter looks reasonably new
I cant see any smoke coming from the back when driving or revving it.
The boost pipe and vac pipes look in good condition with no cracks, holes or anything.

I am really at a loss as to what else it could be causing it? It also has quite a loud rattle when driving or revving. Think it is coming from fuel pump?

Thanks for any help.

 

[clioben182]

Could try taking the egr valve back out and make sure the two valves are seating properly. Would be an idea to get it plugged into a decent diagnostic computer to check for any codes. Possibly an injector leak off test but i don't think it would show anything with the symptoms you have described.

 

[Bob0907]

Thanks for the help! Tried that but egr valve was ok. Unplugged the map sensor and it runs better, so ordered a new one and will fit that.

I have also noticed that there is air in the fuel lines. I had a look at a friends dci 65 and it has much less air in the lines. We bled the filter numerous times until there was no air at all, but after a drive air manages to get into the lines again. What could cause that? The fuel pump is good, as the injectors were getting the same fuel pressure when we cracked the inlets off. The air is mostly in the return from the pump line.

Any help on that? Thanks!

 

[sburrell93]

Do the 65's have a MAF sensor or equivalent? The fact there's no smoke out the back means it's not overfuelling. So as you say it's either a lack of fuel issue, or a sensor is stopping the ecu putting in more fuel because it thinks it's being starved of air.

How much air are we talking in the lines? There's small bubbles in the lines of my dci most of the time, but it's never caused any problems.

 

[Scrooge]

More air bubbles in the fuel lines can sometimes mean the strainer in the tank is blocked. This is an asshat to get to. Will only cost you a new locking ring and seal though.

Egr is probably gone though, just cleaning it more often than not won't solve the issue.

 

[Bob0907]

Do the 65's have a MAF sensor or equivalent? The fact there's no smoke out the back means it's not overfuelling. So as you say it's either a lack of fuel issue, or a sensor is stopping the ecu putting in more fuel because it thinks it's being starved of air.

How much air are we talking in the lines? There's small bubbles in the lines of my dci most of the time, but it's never caused any problems.

Is the MAF another name for a MAP sensor? The one that attaches to the top right of the airbox? Thats the one I unplugged anyway. Its worse than my friends dci, but its better than what mine was before!

More air bubbles in the fuel lines can sometimes mean the strainer in the tank is blocked. This is an asshat to get to. Will only cost you a new locking ring and seal though.

Egr is probably gone though, just cleaning it more often than not won't solve the issue.

Where can I find acess to the strainer? From the top or underneath?

 

[Scrooge]

Under the seats there's a circular panel, under that is the locking ring. Getting that off will be a c**t but one it's off the strainer is at the bottom of the fuel sender unit.

 

[sburrell93]

MAP is manifold air pressure, MAF is mass air flow, both different sensors. Unplugging sensors would probably put the car into a sort of default 'open loop' fuelling mode, which could explain the increase in power. Have you tried just disconnecting the egr valve and running like that?

 

[Bob0907]

Thanks for that scrooge, will have a look at that.

Ah ok, is the map sensor the one at the top? or is that maf? Where is the other one? I havn't tried with the egr valve unplugged. Would that run better if it wasnt working properly? Thanks

 

[sburrell93]

That'll be the map sensor. I'm 99% sure the dci 65 doesn't have a maf sensor.

Unplugging the egr will just make it stay constantly closed. I've had mine unplugged ever since I got the car lol because it was sticking.

 

[GrahamS]

dci has a map sensor. Thats the one that clips onto the airbox. If the car runs better without it plugged in then that's the faulty part. When you replace it it will run better than with it unplugged.

Clean the hard EGR/intake pipe whilst your at it as that will make it run better. Do you get boost or not? I have a boost problem which is the EGR valve

 

[Bob0907]

That'll be the map sensor. I'm 99% sure the dci 65 doesn't have a maf sensor.

Unplugging the egr will just make it stay constantly closed. I've had mine unplugged ever since I got the car lol because it was sticking.

Whats the benefits and or consequences of disconnecting the egr valve? What does the egr valve even do?

dci has a map sensor. Thats the one that clips onto the airbox. If the car runs better without it plugged in then that's the faulty part. When you replace it it will run better than with it unplugged.

Clean the hard EGR/intake pipe whilst your at it as that will make it run better. Do you get boost or not? I have a boost problem which is the EGR valve

Ok ill give the pipe a clean. How would you check if its boosting properly? Im a complete noob to diesels and turbos as you can probably tell lol. First of either iv ever owned!

Thanks for all the help guys

 

[GrahamS]

You can hear when it boosts up. Boost will generally be after 2k. Hissing noise. If it's not boosting properly you will be accelerating extremely slowly, revs won't build up quickly.

My egr valve is sticky at the moment and stopping my boost building up properly, i'm below 2k and put my foot down the revs just won't move. Dropping a gear sorts it out.

Will sound a bit like this but quieter

 

[sburrell93]

The egr (exhaust gas recirculation) valve does basically exactly that. It recirculates some of the exhaust gases and mixes it back in to the air inlet to reduce emissions.

Exhaust gases in a diesel always contain a bit of soot though, and this mixes with oil vapours and builds up as the black gunk you see inside the egr valve, and also the inlet hard pipe that Graham was talking about cleaning out.

Disconnecting it simply stops these gases being recirculated and so keeps inlet air clean. It theoretically could increase power because you're getting more clean air in, so a better burn, but mainly it'll stop the valve and pipe getting gunked up and stop any issues if that's what's causing it.

Drawbacks are that it could throw up a light on the dashboard. That's about it lol. It will technically increase NOx emissions too but since diesels aren't emission tested on an MOT (only smoke tested) this doesn't really matter.