Running problems! 2.1 freshly rebuilt

Post by **dubber91** » 26 Sep 2007, 10:26

Hi guys,

Ive just rebuilt my 2,1 wasserboxer and am having trouble getting it to run right.

When its cold it seems to pull much better and smooth through the gears.
When its warm, the engine stumbles missfires and jumps around if i hold it under part load conditions. Above say 2k rpm and a small 'cruise' throttle, the engine seems to start to jump around. Now given that fuel enrichment during warm up leads to running rich, am i right to assume its fuelling based?

I have timed it at idle to the right most mark on the crank, and the tappets were set to touching plus 1 turn.

I have changed the vaccum hoses, but its a best guess where they were connected......That is to say im not sure its connected correctly. In my eyes one vaccum connection is the same as the other right?

Also, on the throttle linkage there is another arm which doesnt seem to be connected to anything. What does it do?

Cheers guys

Steve

Website · Post by **syncrosimon** » 26 Sep 2007, 17:20

The spare arm on the throttle is for the cruise control vacuum unit to attach to.
Sounds like the air flow meter to me. Unstable running on throttle.
What did she run like before the rebuild, or has this started after?
Simon.

Post by **toomanytoys** » 27 Sep 2007, 05:58

could be all manner of things.. check all connections in the system.. check the vac off the diszzy is going to the correct location on the throttle body (If a DJ... tell us what engine and fueling system it has)
Could be low fuel pressure.. new filter? new fuel lines?
Could well be the airflow meter, these things HAVE to be handle carefully and cannot be dropped and "cleaned" easily...
Check for air leaks on the manifold etc..

hydraulic tappets... just touching and 1/4-1/2 turn preload..

Website · Post by **syncrosimon** » 27 Sep 2007, 06:53

Agree with the above, in my experience any one single item in the fuel injection dept can cause strange things to happen, which you end up trying to compensate for with the tuning.
If I was you I would take it for an hours rolling road tunning by a VW familiar company such as TSR in Bridgewater. They will be able to diagnose the engine at part, full throttle and show what is going on.
You can spend hours and hours swapping and replacing items to no avail, and this is actually quite a straight forward way of getting it sorted.
Try an get a haynes manual, and check that you have got all the parts of the vacuum lines routed properly.
If you can tie it down to fuel injection, then most people establish which bit is not working by swapping out various items for known good ones.
More info would help with the diagnosis. Was the engine running at all before the rebuild?? If so was it doing what it is doing now. If you have rebuilt the engine then the fuel injection should be a doddle. Just time consuming.
As you say she runs better when cold when there is a richer mixture, but only a rolling road will tell you what is really going on. The best place for the timing is as far advanced as she will go without pinking.
simon.

Post by **dubber91** » 28 Sep 2007, 10:03

The engine was running fine, smokey because the gudgeon puin circlip had gone awol, but relatively smoothly.
I have replaced all of the vaccum lines, and i actually have a rolling road at work but i havent put it on yet. Ill give it a go and see.

Has anyonegot a picture of their engine bay so i can make sure the lines are all fitted up correctly?

Steve

Post by **HarryMann** » 28 Sep 2007, 11:12

I have changed the vaccum hoses, but its a best guess where they were connected......That is to say im not sure its connected correctly. In my eyes one vaccum connection is the same as the other right?

Maybe thats where you start then...

Sounds a bit electrical to me... like they say above, I would remake all the electrical plug connections. And redo the earths to engiine, bulkhead and garbox. It's never a bad idea to earth the alternator itself directly to the body with a thick lead at the nearest point, especially on MVs...

Post by **Maplesyrup** » 29 Sep 2007, 16:28

Hello, I have the same 2.1 DJ engine in my van and it runs lovely cold and warm - loads of power very smooth and no misfiring or jumping - except when, as you say at slow cruise throttle, it jumps a little like the clutch is bouncing. At first I thought it may be worn engine mounts. Its done this for as long as myself and the previous 2 owners have had it and may just be a traight of DJ engines. I've learn't to live with it as its easy to dip the clutch and reset the throttle. Don't know if this is helpful but it may be best just to concentrate on getting it running right when warm before trying to address this problem. Good advice above - I'm going to take a look at the airflow meter on mine. Let me know how you get on!

Post by **wasserleaker** » 29 Sep 2007, 18:46

could it be a faulty temp. sensor in the thermostat housing, 'telling' the ECU the engine is still cool and needs more fuel even though it has warmed up? worth checking if the plugs look black and sooty after a warm run, which shows a rich mixture, they should be a light greyish brown colour at normal running temp. just an idea