Trying to get my mothers vn in working order so she feels safe driving it and recently its been getting worse. more so when a mechanic touches it. the problem is that after starting it it can be fine idle normally or if can be idleling quite rough until it stalls. when you select a gear it almost always stalls. the worst thing is that you cant build up the revs because when you are try to rev it it sometimes works but other time exspecially at low speed it has no response and just splutters and back fires at you. But when you release the peddle completly at the last second it has abit of life.
Now heres the items that have been replaced.
Fuel pump 4 months ago fuel filter spark plugs 3 weeks ago spark plug leads Series 2 coild packs (its a 1990 dec series 1 with touches of 2) Crank angle sensor intake manifold gasket intake manifold with all components (found one untouched at the wreckers from a vp)
I have tested the fuel lines. Fuel does make it to the engine. there is spark. the air filter is reasonably clean no visible blockages.
Sorry forgot to mention info about the intake manifold it was a straight swap so all the sensors and injectors that were on it are still on it in the motor while the old ones are still on the old manifold till i clean and put them away for future use maybe
Sounds to me like you have a vacuum leak - could be a split hose or one completely off. You will need to check each and every vacuum hose that attaches to the inlet manifold including the heater tap, vacuum reserve tank and A/C controls. Also possibly see if you can get a complete throttle body with IAC etc off a wreck - they are pretty cheap nowdays. If not then clean the throttle body. Good Luck.
Another thing to check. Disconnect one of the bigger vacuum hose from the throttle body /manifold and create a biggish leak. Let the engine run for about 30 seconds to stabilize then disconnect the IAC(Idle Air Control) Valve On the Throttle Body. Stop the engine and reconnect. Fixed an erratic idle problem i had a few years ago.
Another thing to try is disconnect every hose connected to the Throttle Body and Manifold and plug - air tight. Run the engine and see what happens if its better hook them up one at a time till you find the leak.
DieselBob 797B Cat Dumpy 2513kW 24 Cyl V Weapon of Choice :)