random deceleration

[whozit110]

This is a hard problem to describe. It happens in any gear, while cruising, while starting, more often with the engine well warmed up but occasionally first thing in the morning. Happens most often when changing gears/accelerating.

Have recently replaced fuel filter, distributor cap, plugs, wires, oil filter.
Have cycled 2 bottles of HEET throught the system and have used GUMOUT and spray carb cleaner.

It feels almost as thought I've driven into a big wad of gum. The RPMs will drop off suddenly to about 1k, and if I don't hold back my reflex and give it more gas it will sputter and sometimes stall. If I hold the gas pedal very gently and patiently to about 2k RPM it will eventually "catch" and accelerate normally.

If I am impatient and instinctively hit the gas (like you would in a car that is stalling) the car bucks and sputters like it would if this were my first attempt at using a clutch. I'm sure that's what the people behind me think.

I would greatly appreciate any ideas. It feels like a fuel issue but perhaps it is...electrical?? Any ideas? I don't like driving around like this and would like to take care of this before the snow hits.

Thanks in advance for help....

EDIT -- This is a 1988 carbed Festiva 5 speed w 88k miles.

[ajb999]

check the fuel pump. my brothers pathfinder was doing the same thing and it was the fuel pump going out.

[packrat427]

I have never owned a carb'd Festy , but I would say it could be a fuel pressure issue or a accelerator pump in the carb .

Has it done this for a while , or did it just start , and has it got worse ?

[5.0zone]

Might be the accelerator pump.
Take the breather cover off so you see down into the carb.
With the car off have someone pump the accelerator a few times.
You should see gas being squirted into the carb.
If not the pump is shot and needs to be replaced or carb rebuilt.

[whozit110]

This car's been running spot-on for the last 20k miles/2 years. Recently I had the struts and the clutch replaced and it started happening maybe a couple of weeks after that. It took some time to weed out that it was not a matter of just getting used to the new and very different clutch.

It happens pretty much every day, but some days are better than others. It's possible that it happens less with a full tank of gas. Bumper to bumper traffic is a nightmare, but it happens while driving at even speeds as well - just not as drastically. It's hard to say if it's getting worse. I thought perhaps there was a big old clot of something in the fuel line that would eventually blow out but it doesn't seem to be working out that way for me.

So... the accelerator pump....is this something I can replace myself? Until recently with this baby I'd given up working on cars since college...when everything had a carb and you could set the points with a matchbook cover. I'm older and wider now, lol. The fuel pump, I believe, is under the back seat??

Thanks for you insight, folks. Hope to get to the bottom of this soon.

[Festy46]

The carbed engine has a mechanical fuel pump bolted to the back top right side of the head (as you face the engine). If it seems to work better with a full tank of gas, that could be a weak fuel pump because it has to lift the gas higher to get it out of the top of the tank. Check all your rubber fuel lines in the engine compartment for damage and make sure all the electrical connections to the coil and distributor are tight. You said you recently had a clutch put in. It's possible that the mechanic may have pinched a deteriorating gas hose or didn't get one of the electrical connections completely tight. The carb should have a sight glass on the left side. Take a light and see if it looks like it is at least half full of gas. Start the car and punch the throttle hard (after it is warmed up). If it revs up without hesitation, then your accelerator pump is alright. Put the car in neutral with the wheels blocked and/or the emergency brake on and with the motor running rev it up to about 4000 rpms and hold it there for a minute or so. Watch the gas level in the sight glass. It should stay at the same level all the time. If it drops, then you have a fuel restriction or a bad fuel pump.