XUD9 Valve clearances

[johnny625]

OK, now I measured the valve clearances on my 1.9td Xsara. With the engine stone cold, some of the inlet valves do have 0.3 mm of clearance. The exhaust valves are all pretty much in spec. 


Now will this affect performance as the car does have a stage 1 tune and generally I try to keep it in good nick. It starts well, but at times it drops on performance suddenly then picks up as if nothing had happened. Its not air in the fuel lines or the injection pump.  It just feels weird as if the engine feels choked at times.

Could the "loose" valve clearances cause this? Is it even worth it, taking the cam out and adjusting the valve clearance? Something inside of me tells me that correcting that 0.15 mm difference will make sod all.

[Martin306]

OK, now I measured the valve clearances on my 1.9td Xsara. With the engine stone cold, some of the inlet valves do have 0.3 mm of clearance. The exhaust valves are all pretty much in spec. 


Now will this affect performance as the car does have a stage 1 tune and generally I try to keep it in good nick. It starts well, but at times it drops on performance suddenly then picks up as if nothing had happened. Its not air in the fuel lines or the injection pump.  It just feels weird as if the engine feels choked at times.

Could the "loose" valve clearances cause this? Is it even worth it, taking the cam out and adjusting the valve clearance? Something inside of me tells me that correcting that 0.15 mm difference will make sod all.

The way I see it, is your clearance issue is there 100% of the time. It would not be intermittent.

Not sure what to suggest though, do you have a boost gauge? if so what does it read when you experience this low power?

[johnny625]

When the engine feels choked it doesn't seem to build boost as easily. I do have a boost gauge, generally around 20 psi (1.4 bar) when everything seems to be right.

I just hoped it was the valve clearances or that someone had a similar problem in the past.

I know that sometimes xud9's suffer from tight valve clearances but large valve clearance, that's new to me 

[welshpug]

large is common too, stuff wears.

the bigger the gap the longer the cam turns before opening the valve, and therefore closing earlier, and not lifting off the seat as far.

[johnny625]

Thank you for your suggestions. The valve clearances will be adjusted but not before sorting out the bloody strut bearing...had a nasty case of steering wheel binding and general steering weirdness today. The wheel not returning to center, jerky movements, creaking noises the whole thing, genuinely felt scary to drive at times...

Luckily its just a strut bearing that has collapsed.

[tobytronicstereophonic]

Having worked on Peugeots & Citroens for 36+ years I have found:
A large number of XUD engines seem to have lost a lot of their valve clearance after a few 10s thousand miles, and a few have no perceptible clearance, but all seem to run just fine. In later years, working for myself, I used to correct these anomalies, but it seemed to make no difference to how an engine started or ran...
A more interesting thing I found was when I fitted a brand new cylinder head to one of these engines, using the old original valves/shims (warranty work) they always checked out with perfect valve clearances...
This in my opinion is a fantastic triumph of the PSA's engineering prowess. How a cast alloy component can be made so reproducibly accurate...
Just leave as is, is what I mean :-)

Just though of this to share: in the late 1980s, at a main dealership, I had six Citroen BX Diesel engines in bits at the same time...
I forgot which was which, and put a 17RD head gasket on a 19RD. The 17 having a smaller bore, made the bigger pistons 'kiss' the gasket's fire-ring. It ran fine, just made a click-click-click on idle...

[Mighty306]

Did your boss make you strip it back down again?! 

[ekjdm14]

That's a strange one, (tobytronic's experience) since I've noted tight clearances to actually make a fair difference to cold starting. Perhaps it's down to running on 100% veg oil so it's more sensitive to the slight loss of compression when stone cold, but either way I've never known very slightly large clearances to affect either cold starting or general performance, nor create an intermittent problem like above.

To be honest it does sound more likely to be a fuel issue, or possibly (one I experienced on the silver car last year & only noticed while revving from under the bonnet!) something in the intake isn't up to the task & is collapsing under the draw from the turbo. Either a collapsing pipe between the filter/turbo intake or even the filter itself depending what type you have. When it loses power do you notice any change in smoke, more or less, different colour etc? EGT gauge would probably help determine more if it's a fuelling issue or air restriction. (EGT suddenly less than what you'd expect = fuel issue, sudden increase from what it'd normally be would= lack of air)

One other thought, does your engine have an EGR valve still installed? could possibly be getting sticky or weak & allowing boost to bypass straight to the exhaust side.

[johnny625]

Just to mention, even if I re-did the valve clearances and now they are completely within specs...the intermittent power loss issue seemed to be related to the injection pump.

I had a Lucas injection pump on the car originally, and after 20+ years of service, it seemed to be somewhat worn. I went to a local old school diesel guru, which had a play with the Lucas pump and basically said that there is little that he can do as the pumping plungers inside the rotor of the Lucas are worn.


He told me that it is to be expected after 20+ years, but advised me to put a Bosch VE pump on, as there aren't any new spare parts for the Lucas around here, at least not reasonably priced ones.

So I put Bosch VE from a Citroen ZX on the car, no power loss at all, and bringing the valve clearances within spec seems to have given the engine a bit more torque at low revs, or it could simply be my imagination.