Performance problems

I own a 1985 2.4 720 Nissan Pickup truck (that previously ran perfactly) and it has developed a problem: the engine revves like a roller coaster - it surges up and down then stalls when I stop. So far I changed (and tested with carb cleaner) the vacuum lines; replaced spark plugs and wires, rotor and distributor cap to no avail. Plus when in gear and stopped (with my foot on the clutch) the car will slightly pull forward/backward depending on what gear it is in and is difficult to get in gear. It is a 5 speed. Any suggestions?

It sounds to me like the clutch isn’t fully disengaging (out of adjustment maybe) and is putting a drag on the engine when you are holding it with the brake. That would also make it difficult to shift into gear.

Agreed that the difficult shifting sounds like a clutch problem.
The idle surging sounds like a vacuum leak or a carburetor/carburetor control problem. Carb cleaner is not always the definitive method of testing for a vacuum leak as leaks can exist in the dashboard, carburetor vacuum pods, etc.
A vacuum gauge should be used as this removes all doubt.

At one time 80s era Nissan trucks used an emission control device that could cause a problem like this and they were trouble-prone. This thing was called a BCDD (Boost Controlled Deceleration Device) and was mounted on the top of the right front inner fender. It was designed to control backfiring and hiccuping on deceleration.
Since this is near ancient history I just flat do not remember if this contraption was used on your particular year model or not.


Thanks for responding to my post and I will have a mechanic look at the clutch. I previously sent it to my regular mechanic but they were clueless hence my query (and I will find a different mechanic to do the work). Upon reflection this makes perfact sense but from my past auto ownership I only know the symptoms for what has previously broken down.

Thanks again.