Bucking or jerking of vehicle and Blinking check engine light

[sgould]

Is that the rigid plastic pipe?  If so its the brake servo suction.  The tee piece is only on the automatic.  The extra leg runs to a vacuum pump on the end of the camshaft under the inlet pipe.

[jmblack]

I had a problem with that pipe. It popped off on the down leg of the T on a 2.3t auto. Didn't think of it as the symptom was at idle only. I think it was sucking in air and making the mix too lean. Resulted in nearly stalling then revving high as engine prevented itself from stalling. Under load there was no problem. Easy fix though and worth a change of the small section? The part was quite expensive (I just repaired with a bit of hose) with the valve on but should be easy to source used? Only like that on auto though, I think.

[andcro]

SGould - no not the brake servo pipe - though I have checked that.

This is the pipe that runs around the off side inner wing to the rear of the inlet manifold, under the back of the throttle body. I'm trying to find suitable pipe and valves to make a replacement...

[sgould]

OK.  I think that is the EVAP pipe.  It's for venting the vapour from the fuel tank into the throttle body on engine overrun or into the inlet before the turbo when the turbo is boosting.  It has non-return valves in it to organise this flow.

These valves can stick.  On later cars like mine, there is only one pipe.  No tee down to the turbo.  You could try the "Bolt Mod" but this doesn't eliminate a faulty non-return valve on the pipe to the throttle body.

The bolt mod is simple.  On the APC vale, the one on the top front of the engine with three rubber pipes from it, pull off the top pipe.  Leave the valve end open to air.  Plug the end of the rubber tube with a bolt.

I have attached a picture from the workshop manual of the pipework!!

[sgould]

Here's a modified drawing showing what is on my car.

The red pipe does not exist.

The green pipe is all in one piece.

The blue circles show the old and new positions of the non-return valve.

I think that this design would be better than the bolt mod.

[sgould]

There are other things that could cause uneven running.  Are all three vacuum pipes still attached to the solenoid on the bulkhead in front of the passenger?  These vac pipes get tired and crack or just fall off.

Check all the other small pipes. A pinhole is enough to upset things.  A new set of silicone pipes is a common precaution.


[edit] Where did the blue dash on the red pipe come from??? Ignore it.

[andcro]

That's the pipe chaps.

I've just ordered some hose and one way valves to replace it to see if it improves things, though from what you say I don't think it could be the cause.

Going to have a good look at all the other hoses - I replaced all the small vacuum pipes so they shouldn't be a problem but I'm going to remove each one and check it through - just to be safe.

I'm starting to think it is something more sinister like the throttle body! I'll clean it and see what I find.

Thanks for the helps guys - if you think of anything else please do shout.

Andy

[collywobble]

Check all the other small pipes. A pinhole is enough to upset things.  A new set of silicone pipes is a common precaution.

Will,

I'm interested to know what size silicon pipe you used as I need to replace the vacuum pipes on my 2.2 TiD when the weather improves and the OEM pipe is 3.8mm I.D. and all you can buy is 3 or 4mm I.D.  I assume that the pipes on the petrol engine are the same size as the diesel. when I asked the question before on here I never got a definitive answer as to what size to use.

[sgould]

Yes it's a dilemma.  I only did a few on the old car.

3mm is a tight fit but doable if you are patient and use a lube that disappears, like water.  Otherwise they will be lubed enough to come off in time, perhaps.

I didn't use 4mm but others have done this with success but you may need to put the odd cable tie on the pressure pipes.

[Max Headroom]

...and use a lube that disappears, like water. 

A very very thin film of silicone grease?

[collywobble]

...and use a lube that disappears, like water. 

A very very thin film of silicone grease?

What about using a gentle source of heat such as a hairdryer to soften the end of the silicon tube so when it cools it shrinks around the spigot on the part you are attaching it to?

[Steve440]

What about using a gentle source of heat such as a hairdryer to soften the end of the silicon tube so when it cools it shrinks around the spigot on the part you are attaching it to?
[/quote]

Or a cup of boiling water? Dip the end in for a few seconds and push it on quickly?

Steve

[collywobble]

Good idea Steve, easier than waving SWMBO's hair dryer around under the bonnet - together with the repercussions for using it in the first place!

[Audax]

I have a cheap hair dryer for DIY jobs. Cost about £8 from Argos.

[Max Headroom]

I have a cheap hair dryer for DIY jobs.