Help intermittent acceleration problem

I have a 1990 Nissan Stanza manual 5 speed that runs normally the majority of the time, but sometimes something gets messed up and it won’t let the RPMs get up to normal. When it gets in that condition it revs up and drops down, revs up and drops down. This causes a bucking behavior when trying to accelerate while shifting gears after having slowed down to make a turn. It will accelerate a little, then start the bucking. When I hold in the clutch and try to rev it up that’s when it does the rev up and drop down but during those times it never revs up very high. While it’s in normal condition after making a turn and going through the gears to accelerate after shifting to each successive gear, it will accelerate sort of slowly then at a certain point it feels like something kicks in and it begins to accelerate more rapidly. When the problem is occurring, after shifting gears it will accelerate sort of slowly, then when it should begin to accelerate more rapidly instead it begins the bucking behavior. What seems to bring on the problem condition is when I use the motor to slow down, not downshifting but just letting off the gas pedal. It’s like the back pressure (or whatever) engages the problem.

When I turn off the ignition and start the car again the problem is gone instantly no matter how quickly I do that. I’ve had this car for many years and it has only recently started this sort of behavior. Does this sound familiar to anyone?

Thank you for any help!

Maine, USA

Do you have a check engine light on? if so, post it here to help you better
Most Autoparts stores will scan your vehicle for codes for free.
I am not familiar with your vehicle, but it seems like it might be a fuel related issue. if you have a fuel filter that can be replaced, when was the last time it was replaced?
From what I have read online, one known issue with this vehicle is…

Rough running, poor fuel economy, or poor power may be caused by clogged intake manifold runners allowing excessive EGR flow to some cylinders. (1990-92)

This is an OBD1 car…doubtful the auto parts stores have anything that can read the codes.

You’d have a hard time finding any shop that can read codes on this car.

I own a manual trans OBD I Corolla, similar vintage, and experience that symptom a couple of times. First case it was a faulty idle air control valve. Solved by disabling the function completely, as that part is useful mostly used for improved cold weather idling. Not overly cold in San Jose. Second case, fuel injectors needed cleaning treatment. With this problem, good idea to first make sure throttle position sensor is working and properly adjusted.

Could be other problems too. Engine needs basic tune-up, set idle rpm and ignition timing to spec, air filter plugged, problem with exhaust system, etc. That’s a frustrating problem, but I expect once your shop takes a look, won’t be overly difficult to fix. Best of luck.

OP probably already knows how to read the car’s diagnostic codes. OBD I cars usually have that function built in, set a test-switch or jumper, codes blink on light on the dashboard, sort of like Morse-code. Works well, not nearly as many codes on OBD I cars as OBD II cars.