Turbo diseasel tech advice needed.

[Pete-M]

Because I'm particularly crap at diesels, I have a couple of questions to ask those who actually know a bit about 'em. It's related to the 2004 2.2 dCi ESpazz I keep trying to get running properly.

 

Past history is this. Car ran fine for 95,000 miles then the turbo went causing the engine to run on its own oil. Luckily, it was stopped before it grenaded. Engine was fully reconditioned, all the pipes cleaned out and a new turbo, DMF and clutch fitted approximately 6000 miles ago. Since then, it's never been right.

 

Last week I ran it for a few days, interrogated the various ECUs and other than the infamous "Heater plug circuit" fault I've been told that virtually all 2.2 dCi Renaults suffer from it's showing up as being fine. All faults clear other than that one. As it starts perfectly, I can live with that fault for now. I also cleaned the air flow meter and reset everything.

 

It drove better after that, but it's still not right. Drinks more fuel than it should, feels down on power and torque. At low revs it feels ok, but it's lacking torque. Higher revs (2000-3500) it pulls ok but not like it should. Feels almost as if it's running on 3.5 cylinders. No smoke, doesn't burn oil, just feels a bit like it's misfiring slightly. Very flat in high gears at low revs.

 

Tonight I had a look at a few of the intercooler pipes - mainly the ones I could get to as it was getting dark and they're a bit buried on it. A couple weren't fitted quite right, so I adjusted them so they're sitting right and did what I could to get a better seal. After that it's better, but still not quite as it should be. Still feels down on power but it's better.

 

Now, as I'm crap at turbo diesels I'm wondering if low boost pressure would cause it to feel a bit three legged? I'll check all the other boost pipes asap, but if the turbo isn't boosting properly due to pipe leaks would that cause it to run rough under medium loads when the turbo should be doing it's thang?

 

There are no whistles suggesting boost leaks, but it's obviously not right and I'm racking ye olde noggin trying to work out wtf could be wrong with it (other than being the worst engine ever to enter production, obviously).

 

Any pointers? It has had fuel system cleaners through it and other than being crap nothing seems to be too far out. No nasty noises or anything obviously wrong.

[ashmicro]

The only thing I can suggest is "intermittent loss of signal from crankshaft position sensor" (AutoData 3.38). Might not show up on a FCR. Do Renners of that vintage still use volatile memory? If so, perhaps the disconnecting the battery trick might yield some result.

 

Good luck, I'm glad you're doing it and not me!

[Pete-M]

The ECU logs bloody everything, so it's unlikely to be that.

 

After some googlage I'm thinking it has to be a pipe not sitting properly somewhere. Either something to do with the VNT or similar.

[warren t claim]

[michael1703]

What makes you think its ECU related?

 

Is it lacking at all rpm's or just under load?

[Rocket88]

You may be right in suspecting an air leak. Find someone in your vicinity who has a smoke machine, you'll know in seconds!

Brilliant bits of kit, works by pumping smoke [they use baby oil to make the smoke.............] into the air intake, shows any leaks instantly.

[panhard65]

You could try unplugging the maf sensor and give it a run up the road. This works with V.W's when they are down on power and doesn't show up as a fault code for some reason. I would also get it compression checked just in case

[Micrashed]

Sticky EGR?

If they stick open it will cause the faults you describe. That said I would expect this to show as a fault code.

[dieselnutjob]

you can try blocking the EGR completely and see if it makes a difference. It may or may not cause it to throw an error code but it will at least tell you if the EGR is open more than it should be.

 

On the 607 the EGR is blocked with a piece of sardine tin cut to shape with a pair of scissors. It works.

Basically there is a pipe from the exhaust manifold to the inlet manifold, with a valve in the middle that controls how much of its own shit the engine sucks on instead of nice clean air. Block that pipe anywhere that you can.

 

If blocking the EGR transforms the car (even if it causes an error light to come on) then that would suggest that the EGR valve, or possibly activating solenoid is tired.

 

It could also be that your new turbo is a bit crap and not boosting properly. You need to get the car on a diagnostic tool that shows boost, or inlet manifold pressure in real time and drive around seeing if you get decent boost. If you have even an EOBD scanner (or a Renault one) the show manifold pressure on many diesels so worth trying. I would imagine that you are looking for 1 bar boost from 2000rpm or so? Turbos are computer controlled these days and the ECU may well ask for a bit of boost even at medium throttle. If you can access a similar car that drives well and compare numbers that that would be good.

 

If you get low boost it doesn't necessarily condemn the turbo. It could be a vacuum leak or a tired actuating solenoid.

 

A friend of mine changed the turbo on a Saab 2.2 TiD for an "OEM" one a few months ago and he says it has lost its sparkle since then so it does make me wonder if these copy turbos are as good as the original ones.

 

Lastly mass air flow sensors can cause crap running and the ECU doesn't seem to be able to tell that its a crap MAF rather than crap airflow. I don't have a solution to this as none of mine ever failed.

[Pete-M]

Checked all the boost pipes I can get to (most of 'em) and got them to seal about as well as I can. It is improving all the time.

 

Next step is a new air mass sensor methinks, if that doesn't work then it'll just get driven until it dies. Shouldn't take too long, even with all the new bits.