I have a 1990 subaru sambar 5 speed 4x4 . The truck starts fine , idles fine ... but when I'm accelerating up through each gear there is a point about mid-way where the engine hesitates . Once I have reached the upper R P M's in each gear , the truck runs fine . What would cause this . Any help would be great ! Thanks . ( also , in neutral the truck revs. up smoothly ... no problem )
N/A subaru with a carburator, or EFI (with or without supercharger)? Excess air (vacuum leak?), low fuel pressure (bad pump, clogged filters), or bad spark plugs or wires could cause this. If you have EFI, it could be a defective MAP sensor.
Thanks for the reply Spikefiend ... my truck is N/A and carburated . I just changed the fuel filter recently , but the fuel that is in the tank is quite old ! Would that be any issue ?
I think that's very likely. I'd siphon out the old gas and put some new stuff in there and give that a shot. Symptoms of Bad Gas
Once again SpikeFiend ... thanks so much for your advice . It's much appreciated ! As soon as I get time I'll switch into trouble-shooting mode . Your help has been great !
Have you resolved your problem? I’d like to know if you did and your remedy because I’ve have an identical issue!
trktrd Tell you what, if we don’t get a response, I’ll keep in touch with you. I’m going to dig a little deeper and I’ll connect a vacuum gauge and see what’s up. I suspect it’s vacuum related.
Have you checked the ignition coil? Could it be failing? Is the problem worse after running a while when the coil may be hot?
There is a diaphram that opens up the venturi when you go WOT. Difficult to work on as you can't check it when parked as you have to be WOT for a bit and the engine would over rev in neutral. There is an adjustment for this diaphram and it should have some paint on it to show it hasn't been played with. It could be there, but I warn you, playing with it can make a mess of your carb and getting it working right can take a long time of driving, adjusting and driving again to get it right. I set up a gopro camera looking at the linkage to that diaphram and watched to see if it worked when going WOT on the road.
