Running rough

[MF74]

I'm having problems with my 1.9DG engine. It's a remanufactured VEGE unit around 3 years old and it's only done about 8k miles.

I did a tour of the south coast (nearly a 1000 miles) and it ran fine, then it sat unused for 2 months.

On its next trip out it was hesitating when pulling away, kangarooing slightly, mainly when in 2nd gear but there was also a bad vibration around 40 - 60mph. At first I thought the vibration was a wheel so I checked all the wheels and even swapped the spare onto each wheel but they were all fine, so it wasn't the wheels causing it.

I've since found that the vibration is being caused by the engine rocking - with the engine running I took the ignition leads off the distributer cap in turn for each cylinder. When I took the leads off to both right hand cylinders (1 & 2) there was no difference to the engine note, so something was not right there.

So I checked the plugs, they were fine (nice and dry and whitish grey). I put a new disi cap and rotor arm on and tried new ignition leads (even took the metal shrouds off them), but none of this made any difference. I had a compression test done and the results were cylinder one 120, cyl two 125, cyl three 135 and cyl four 150.

I reset the tappet screws (screwed in until they touched then a further 1.5 turns in). After that cylinder 1 is now 135 and 2 is now 130. This has made a big improvement in the running, but there is still a hesitation when accelerating and the vibration is still there (but nowhere near as bad). It seems the rough running is at the same point in the rev range in each gear.

I've checked all fuel filters & checked for air leaks. It had fresh oil 1200 miles ago. The strange thing is that it idles well and revs cleanly when stationary, it's only when you're on the move it plays up.

Any thoughts on what to try next?
Thanks.

[kevtherev]

Does the engine advance the spark enough ..and correctly?
I notice that you only reset the tappets on one side , is there a reason you did that?...apart from it works ok

[itchyfeet]

there was also a bad vibration around 40 - 60mph.

I've since found that the vibration is being caused by the engine rocking - with the engine running I took the ignition leads off the distributer cap in turn for each cylinder. When I took the leads off to both right hand cylinders (1 & 2) there was no difference to the engine note, so something was not right there.

It seems the rough running is at the same point in the rev range in each gear.

The strange thing is that it idles well and revs cleanly when stationary, it's only when you're on the move it plays up.

When you took the leads off one and two and it made no difference well you can't do that while driving and you say it runs well when idling so that sounds strange to me.

Check the second choke vac unit is operating.

[Ralf85]

Partially blocked fuel filter?

[itchyfeet]

Partially blocked fuel filter?

I'd expect a slightly different symptom happening after a period of time over a certain speed rather than always at the same revs in each gear but certainly worth checking.

[marlinowner]

Probably not relevant in this case, but not firing on 1 and 2 would make me wonder if leads for them have been transposed whilst trying different tests.

[MF74]

Thanks for all the replies.

I did adjust the tappets on both sides + checked for a spark (ok). Also double checked leads in correct positions.

[kevtherev]

there was also a bad vibration around 40 - 60mph.

I've since found that the vibration is being caused by the engine rocking - with the engine running I took the ignition leads off the distributer cap in turn for each cylinder. When I took the leads off to both right hand cylinders (1 & 2) there was no difference to the engine note, so something was not right there.

It seems the rough running is at the same point in the rev range in each gear.

The strange thing is that it idles well and revs cleanly when stationary, it's only when you're on the move it plays up.

Check the second choke vac unit is operating.

Good call itchy

[MF74]

''Check the second choke vac unit is operating.''

Thanks. Could you tell me more about this please. Where would I find it and how would I test it?

[itchyfeet]

its this disc shaped unit here, as you can see it attaches to a cam which means it can't physically open the throttle by the cream plastic part until the throttle is sufficiently open already ( this stops it opening at idle when vac is high just opens at high throttle when vac is high)

After this point if there is enough vacuum then it should open the second throttle.

So to test you need to disconnect the vac pipe form the carb, open the throttle sufficiently ( brick on the pedal means you have both hands free) then suck on the pipe and watch the second throttle with a torch.
In practice you can't get your mouth to the short pipe with the carb in place so if you still have the original small diameter plastic tube on your dizzy vac pipe you can borrow it to lengthen this pipe.

if it won't open or you can suck fresh air it's not working.

If it does work then double check the drillings in the carb are not blocked by borrowing the dizzy vac pipe attaching the dizzy pipe to the carb and blowing into the carb, you should be able to blow air in.

[kevtherev]

It is akin to a bloke with a bucket of petrol standing ready to chuck it in your engine when you floor it

[MF74]

Thanks for all the advice, I will give it a try.