2.1 (XUD11) throttle damper?

[Old-Guy]

The VSX has an irritating habit, worse until engine gets up to temperature, of the revs surging as I change gear. No, it's not an inability to co-ordinate both feet and left hand! Am I right in vaguely remembering reading something about a mechanical damper on this Lucas pump? Or is this something in the ECU mapping?

I wasn't going to bother over much about sorting minor problems with the VSX as I didn't intend keeping it for long, but the better half is out of action for the next couple of months so I won't have any time to work on the Green Lady, by which time it will be winter..... In the the meantime, we depend on the VSX.

If it's a simple fix that won't take more than an hour or so - like lubricating a mechanical damper - then it's worth doing.

[Mandrake]

Not enough slack in the throttle cable adjustment ?

[Old-Guy]

What throttle cable? It's bloody fly-by-wire! One of the reasons I don't want to keep the car; give the the good old Bosch pump with no electrics, let alone ECU. Yes, I'm a Luddite believer in the sound old mechanical engineering principle K.I.S.S.

[Dommo]

There's a throttle cable from the pedal up to the potentiometer underneath (and sort of beside) the air filter housing. Get someone to press the pedal up and down (engine off) while looking around/below the air box, you'll see it. Check it's not slow to return.

I have a feeling my old 2.1TD had similar behavior, as does my parent's Saab - albeit a petrol Saab - to attempt to make crap drivers seem smooth. However if you're normally a smooth driver it tends to catch you out as you don't entirely lift off the throttle during a gear change, so the revs are almost where they should be for the next gear by the time you bring the clutch up, if you know what I mean? However with it trying to keep the revs up for you, and you adding to it, it makes for a revvy gear change!

[Mandrake]

Another thought, where is the bite point of the clutch and how much life does the clutch have left ? The only cars that I've driven where the revs surged during a gear change were due to the clutch being almost worn out and the pedal having a very high bite point.

You can compensate up to a point by modifying your pedal technique but if its badly worn the revs will still surge.

[Old-Guy]

Gentlemen, thanks for all the information and advice. I understood the throttle potentiometer was actually on the pedal, perhaps I'm confused with Ford practise.

The clutch bite point is pretty high (at 92,000 may still be on the original clutch?), and when I test drove the car, I put the revvy gear-changes down to this and a lack of familiarity with this car's idiosyncrasies. I've been accustomed to driving lots of different vehicles so I know when it's a matter of unfamiliarity or the vehicle has a problem. I've encountered the identical problem with the latest Transit vans which was easily fixed - how I don't know and not sufficiently interested at the time to care.

In all cases that I've come across, the 'throttle' is slow to close when you lift off so the revs shoot up as you dip the clutch - hence my question about a damper. I vaguely remember someone (Jim?) talking about a throttle damper but I didn't take a lot of notice as the subject wasn't XUD9-with-Bosch.

[CitroJim]

There's no damper on an EPIC Guy, it's all done electronically..

The throttle pot is under the airbox and is cable operated from the pedal!

The likely causes of surging are air ingress (the EPIC is unbelievably sensitive to it) or ESOS valves beginning to fail. The problem is most likely the former and leakoff pipes are a big suspect.

The health of the ESOS valves can be checked by running Lexia actuator tests and also crudely by seeing how quickly the engine dies after ignition switch-off - if it runs on for a few seconds then the ESOS Valves are getting worn...