Hesitation at 2200 RPM
 

Hello everyone; I'm new. I know a bit about VW TDis but nothing about Volvo/Ford/PSA so I'm hoping for your help on our newly acquired 2006 S40 Euro 3 2.0D.

It's a lovely machine but there are a few teething problems to sort out. The first of these I would like to address is a hesitation when accelerating through 2200 RPM. Afterwards there's also a smaller hesitation accelerating through 2800 RPM. Other than that, it pulls very well indeed. These hesitations are accompanied by a faint sound I can only describe as like a note played on a clapped out reed organ.

In the Torque app I've plotted both fuel rail pressure and boost pressure against engine speed. I can't see any pressure loss in either at the affected RPMs although I'm not convinced of the accuracy of the boost calculation in Torque. I do notice that full boost coincides with the first hesitation at 2200 RPM.

It would make sense to me that the ECU is overcompensating after a high boost spike causing it to back off too much.

Are the these turbo units variable-vane or are they fitted with a wastegate? I'm trying to understand the accompanying noise.

Thank you in advance for any help you can give.

Hi,

Can I ask how you are logging the data?

Thanks

Nothing very scientific I assure you! I have an OBDLink MX talking to the Torque Pro app running on Android. Under "Graphing" I chose to plot boost against engine speed as a scattergram. I started logging when in 3rd gear at low revs, then went through the revs at WOT a few times. I did the same while plotting fuel rail pressure. After a while the graph builds up two distinct lines - one when accelerating and the other when slowing.

I had a crank sensor go on another car which gave the hesitation after 2200rpm (or somewhere very close to that think it might have been 2500rpm)

Is it a bit of a chirpping sound you get? I've had overboost on another car and that gives a chirp but not until you let off the pedal (to change gear etc). As you let off the pedal you get a flutter noise.

Check for any splits in any of the pipes and make sure they are all secure

I would expect a defective crank sensor to throw a code and there are no codes being generated.

The noise is a tone rather than a chirp and happens on-throttle.

I looked at the vacuum pipes as you suggested and some of them are quite soft. Maybe one is collapsing and making the reedy noise as the air is drawn through. I have some spare tubing I can try as soon as this damn rain stops!

Thanks dude.

and exhaust manifold nuts sits snug? Check the DP bolts whilst there. Both are known to come loose, resulting in o2 leak prior to o2 sensor. Not necessarily leaking exhaust but pulling in air, messing with o2 reading.

I'll certainly ask my man-wot-does to take a look at the exhaust manifold next time it's up in the air. DP? I'm aware of one meaning but I don't think the car is that kinky.

Thanks.

DP=Downpipe. Connection between it and exhaust manifold :-)

V40 TD Engine rattle
 

I know I am probably following the wrong thread, but am hoping for assistance with this ongoing issue. I have spent £500 on getting the egr valve checked, a new maf, and the manual fuel pump?? replaced. All this was to alleviate surging whilst cruising. I explained to the independent garage that I also experienced a rattle at approx 1500 to 2000 rpm and a slight hesitation. The rattle sounds like a diesel engine running with petrol in it (I did that to a vauxhall and it sounded like "pinging") The above "cure" has only helped with minimal reduction in the surging and continued engine rattling. The engine does not smoke or use oil. Fuel consumption is still excellent at 11 miles per litre.
The garage man says that he now suspects the turbo.... I enquired at Aceturbos in essex and they seem to think that the rattle may be caused by the Vnt ? variable vane "wastegate". I have checked the actuator vacuum diaphragm unit and it moves easily. I have also had someone watch the actuator to confirm it is operational - thus proving the solenoid is working. Could this annoying rattle be caused by heavy carbon deposits preventing the vanes from opening?

Any advice would be appreciated - I don't particularly want to fit a new/reconditioned turbo and find that the problem prevails.

To follow up, I decided to replace the turbo vacuum pressure converter and it seems to have done the trick.

I suspect that the old one was releasing the vacuum too quickly when the system got to peak boost. This was causing the wastegate (or is it VNT?) to open fully with boost dropping dramatically. Then when the ECU noticed, it was piling on the boost again until peak boost again etc. The result was surging under load.

Insomnia has its uses.

Sorry losttribe - I have no idea what your problem was. I hope you got it fixed.