T25 1.9DG Engine running rough

[markhouston72]

I’m having a bit of an issue with my van just now, hope someone can point me in the right direction. I had left the van sitting for a couple of weeks and when I went back out to it to start it, it started behaving funny.

It seems to be miss firing quite a bit on start up, sometimes it will start on 2 cylinders (it sounds like anyway) then you get 3 before they all get going, sometime it starts on 3 before getting the forth. Also when driving it sometimes feels a bit sluggish power wise too, nothing massively noticeable. On the very odd occasion when driving you get a bit of a back fire when coming off the throttle. Idle is very lumpy too, where it used to want to idle quite fast, now you’re lucky if you can keep it running it’s so slow.

Also, the day it started doing this once it was running there seemed to be quite a bit of knocking coming from the engine which goes away when it gets warmer. This seems to have gone now completely after changing to 20W/50 and a can of STP.

Did notice that the engine mounts were completely shot (at low revs I could make the engine shake so much I thought it was going to twist its self off the van) which I replaced on Sunday (took all day cause the new ones didn’t fit, so needed to be “made” to fit). This has cured that problem at least. I’m hoping the shaking hasn’t caused some real damage.

Anyway, I’m going to start this week with replacing the plugs and HT leads. Any ideas as to where to go next?

[kevtherev]

I would be replacing the fuel filter and cleaning the carb out.
then checking for air leaks in the system.
Which cylinders fail to fire?
left side would indicate a leaking servo hose (common)

the loud tapping is quite normal for flat four high mileage engines.. lack of use lets the hydraulic valves leak down.
20/50 will do a good job keeping them quiet.. I never use additives

[markhouston72]

Well lots of busy work over the weekend on the van, to varying degrees of success.

Changed the spark plugs (I ordered the plug leads from JustKampers but they sent the wrong ones), cleaned up the dizzy cap and rotor arm etc, sprayed DW on just about everything I could think of that might leak air with no change in engine note.

The thing must be running really rich though. The spark plugs were jet back when I took them out (dry though, thankfully) and I’m getting a bit of black smoke out the exhaust plus some evidence on the drive of what looks like black sooty splatters of some sort of liquid which looks like it’s come out of the exhaust too, hoping its un-burnt petrol and not oil, could not recreate this though. Also when I adjusted the idle screw for the card it didn't make much difference what I did to it, it still coughed and spluttered and didn't relly idle any better.

So I guess my main question now is how do I lean the engine back a bit?

[kevtherev]

Plugs will be black after a cold engine tickover, should use them as a guide after a run over 3000 rpm
there's an idle mixture screw on the carb... I would use a gas analyser to set up the mixture

But, I would first check over fuelling by a faulty choke i.e. stuck on (Choke pull down unit failed, busted bi metallic return spring, float chamber stop "cock" fulty etc )

[Briggsjag]

I've just had the same problem as yourself, it wasnt until i had a look at night that i noticed a slight arc between HT leads. Replaced them and problem seems to have gone. As for the knocking, i've been told my van has a lazy/sticking lifter or valve, it will free its self after a few miles of driving. doing an oil change today so hopefully that will stop it. hope this helps.

[toomanytoys]

MH72, can you fill out your profilr please, that way we know where in the country you might be, there may be a mechanic near you that can help out...

Before leaning off the engine, coz you think its rich.. has all the other factors been addressed?? like timing, is the carb faulty.. (these carbs really benefit from a rebuild now.. gasket kit and set up works wonders..) Air intake/filter clear?.. Have you been up the road in it for a good run and then seen if the plugs are still black.. sitting on a drive or just up and down the road for 5 mins isnt the way to set up or assess an engine.. I am guessing it get started and used only for short trips a lot.. as the "knocky" tappets is what happens if they dont go far..

[markhouston72]

I'll try and update my profile, sorry about that. Anyway, I'm up in Central Scotland but was down for Vanfest at the weekend and managed to get a place booked for the Tuning Workshop. To cut a long story short the tuning guys thing that I need an carb rebuild. They turned the mixture screw right in on the carb and still the CO2 reading was way to high so they think its an issue with the bottom end of the carb. So I guess I'm looking at a rebuild or reconditioned unit.

I think I'll try disconnect the automatic choke first though, just to make sure

[clartsonly]

you can check the choke by taking the filter box off and looking to see if the butterfly has moved, you can clean the carb by revving the nuts off it and then putting your bare hand (not latex gloves else they will tear and you will get something stuck in the jets) over the top of the carb. It will drag a load of fuel through and give it a good clean up.

make sure you always run it for 20 minutes before you class it is "warmed up".

try jamming a screwdriver under the throtte cable to get the revs up a bit then (after you have marked its existing position) just turn the distributer as tiny bit each way and listen to how it sounds, I tried following the timing gun and haynes instructions for mine to set the timing up and it made it run like sh*t.

also check the engine breather pipe that returns to the filter box, if it is full of gunk it will not breath properly and push emulsified oil/gunk back into the carbs.

good luck... dont always trust garages.... VW Campers are a different story they have a mind of their own, certain pipes may be disconnected by the previous owner - maybe they fell off! maybe they were removed to keep it running right.