F.I. Bus miss

[busnerd]

I've got a '78 bus with fuel injection that has developed quite a pronounced miss under acceleration. I have replaced the fuel filter, as I thought it may be a starvation thing but that was not the cause. I put a new cap and rotor on it as the old ones had lots of carbon built up. But the van still bucks under load. I don't know where to go from here? The points are set to 50 degrees and it's timed correctly. I don't know much about fuel injection so any ideas would be great. Also.... how can you tell if the engine has hydraulic lifters? as i guess it could be a valve adjustment thing if they aren't hydraulic.
thanks for your help.

[koho60]

I had a 77 that had the same problem. It turned out that there is a heat sensor at the #3 cylinder that went bad. As for your valves I don't know. There is a article in type2.com that explains what valves you have.
good luck
JEFFRO

[canabus]

possibly the pump is noy pushing the desired fuel,or something resticting the line.

[westy78]

Does it miss just under acceleration or does it do it while cruising under partial throttle also? I had a problem with my 78 that I thought would be solved by a tune up. It would miss under acceleration but only at a certain throttle position. Turned out to be a bad AFM. At that particular throttle position the track that the potentiometer moved over was worn and was not sending the correct signal to the injectors.

If this is a stock 78 it should be hydraulic lifters. I dont think there is a way to tell without pulling the push rods or lifters out. If the valve train is quiet than it is most likely hydraulic or all of your valves are to tight which is not good.

[NeverHadaBeetle]

I have had the same problems as Westy78 on the AFMs where one spot on the contact board is worn and causes a hard miss. A miss caused by this type of problem is actually ocurring under normal cruising also, but it's just not as noticeable as it is under hard acceleration. You can sometimes remove the cover on the AFM and actually see the worn spot that's causing this. If you need to replace the AFM then check Ebay since your bus is still running and this problem shouldn't leave you stranded. You should be able to find one under $35 and I see them all the time for under $20. Make certain you get one with 7 pins in the plug which were 1977-83 only. In 1975-76 they had 6-pin plugs. You could also go ahead and replace the cylinder head temp switch also. The CHT is kind of a maintenance item anyway and they only cost about $15. You can replace it in about 5 minutes so it's cheap and easy. With regards to your lifters they should be hydraulic in a 1978. You can remove a valve cover and see if a magnet will stick to the push rod itself. Hydraulic lifters used steel pushrods and a magnet will stick, but the solid lifters used aluminum push rods and a magnet will not stick. Good luck.

[busnerd]

Thanks for all the good advice guys, i will look into the AFM and change the cylinder head temp sensor as well.
later.