I'm currently running Partner MY2003, 1.9D (1,868 l), it's the DW8B engine coded WJY. The block (with everything inside so cylinders, crankshaft etc.) has been recently swapped due to heavily worn out cylinder(s), it was pressuring into oil sump, so it could not start under 15 °C outside, way too bad compression. Everything else (head, sump, fuel pump etc.) has been kept from the previous block (the one with worn out cylinders) as it was running OK otherwise. Since than started right away. Also the exhaust piping broke recently due to corrosion, the first and last pieces have been replaced as a whole (so both noise suppressors), some new pipes were replaced as well.
I've run some 2500 km with, but recently noticed gradual loss of power, first it starting only mildly jerking (if that's the correct english term), most likely missfires. It got worse over last 500 km, few days ago I could barely keep 100-110 km/h on highway, now it gets to the point I can barely keep 80 km/h especially uphill. I can feel it easily that the engine misses out the haul.
Now what I know so far:
- it only happens once the engine warms, runs more or less normally while cold, I can throttle all the way to 3000 RPM and it still has power and can increase speed; once it warms, it starts missfiring since about 1/3rd throttle, if I go all the way to full throttle it gets worse, in the extreme to a point it almost does not run at all (but by the momentum of the car)
- runs completely fine on idle, so first I suspected fuel filter cause Felicia with VW AEF engine behaves similarly when filter is totally clogged and it both has similar Lucas fuel pumps, it was somewhat dirty but no real change in behaviour; there is no air in the fuel system, when I opened the fuel filter box, it was completely filled with fuel without a single buble
- do not notice any black smoke or anything
- I got an advice to remove the bottom hose from the underpressure regulation of the (so called) butterfly valve; it seemed to help at first but maybe it was just that everything cooled down while I've been messing around it cause it started missfiring after some 8 kilometers again
- not sure whether this is connected, but I noticed almost instantly when I started driving it, if I do not wait some 5 seconds between turning the key on, and starting the engine - while it is already warm - but start the engine right after inserting the key, it either dies within few seconds, or, if I hold it up with throttle, RPMs shoot out to some 2500 and pretty much stay there even if I release the throttle. Computer beeps doing that.
I should also add I am adding very clean (but used) hydraulic (mineral) oil to the fuel mixture as these indirect ignition-swirl chamber engines generally run OK on that (two AEF engine cars I run already have more than 50000 km on them), but it may be producing a bit more of sluge which may get to intake through EGR which is not blanked ATM. So I am thinking, could the butterfly valve be sludged so much that it has problems getting air, or possibly the valve gets stuck in some position? But than why would it only manifest when the engine is warm? So could it be also something on the Lucas pump?
), I could clearly see it's been pulling a LOT of air through the fuel hose from the very tank.