YACT: acceleration hesitation

[Barnaby W. Füi]

I have a 79 lesabre, which is in mostly ok mechanical shape, despite looking like crap with some rust and spray paint and whatnot.

So whenever I stomp on the gas, it will usually instead roaring to life, sometimes (most of the time really) bog down as if I let off of the gas. After a second or so, it'll catch its breath or whatever it's doing, and then it'll speed up like you'd expect it to. It seems to happen less when the car's been running for a while, and when I first turn it on, it'll actually die once in a while when I step on the gas the first time after starting up, i.e. it's doing the bog down thing, but just so extreme that it dies.

Ideas?

edit: oh and when starting it after it's been off for a while, I have to give it lots of gas. not sure if that's related or not.

 

[Eli]

Yes, it is related.

One word: Choke.

Actually, the choke shouldn't be on/affect anything when the engine is already warmed up. It is definately fuel system related, though. Accelerator pump? Fuel pump? Filter? etc...

 

[Barnaby W. Füi]

A friend of mine a while back mentioned he thought it might be the fuel pump.

 

[zimu]

my older car had same issues. i think its just the deal with older cars taking longer to warm up. especially in your case engine is damn old, when you stomp the gas you literally drown the engine with gas and it takes a second for it to overcome the drowing, at which point it picks up revs.

but its like flooding the engine and having the car not start due to that. fuel management system is outta date, doesn't happen in newer cars.

 

[Barnaby W. Füi]

Gotta be something I can do about it though, don't ya think?

 

[StageLeft]

Definitely something to do with either fuel or air I'd like to see what the problem is too...I have a similar, though incredibly mild, issue from my 97. When I give it WOT it sometimes does what yours does, though it's to such a small degree that a passenger probably wouldn't notice.

 

[Eli]

Originally posted by: zimu
my older car had same issues. i think its just the deal with older cars taking longer to warm up. especially in your case engine is damn old, when you stomp the gas you literally drown the engine with gas and it takes a second for it to overcome the drowing, at which point it picks up revs.

but its like flooding the engine and having the car not start due to that. fuel management system is outta date, doesn't happen in newer cars.

I believe you have it backwards.

Hesitation when stomping on the gas is almost always caused by a lean condition.

When an engine is running too rich, it will generally not hesitate when you stomp the gas. However, it will severely lack power in the upper RPM range- if it can even get there.

 

[Aimster]

Fuel filter there buddy .. change it
Air filter there buddy .. change it
Spark longs .. make sure they have been changed

Most diff fuel filter

 

[shekondar]

Could be a timing problem. Older engines had a vacuum actuator inside the distributor that advances the timing when you accelerate - sounds like this could be bad (I had an old Chevy pickup with the same problem). Vacuum leaks can also cause this.

Of course, wouldn't hurt to check the other things already suggested (fuel pump, filter, spark plugs, etc.)

The hard starting when cold definitely sounds like a choke problem.

 

[Quixfire]

It?s most likely the accelerator pump causing the problem. The accelerator pump injects a stream of fuel into the throttle bores when the throttle plates are opened quickly to prevent the engine from a lean run condition caused by the immediate intake of air. When the pump wears out it no longer supplies enough fuel to compensate for the increase in air volume through the intake.

If you know how to rebuild the carburetor this can be a simple fix of replacing the pump. If you don't I would find a mechanic that has the necessary skills to do the repair. Find an old timer like me that has worked on these older vehicle and you should be OK.

 

[Barnaby W. Füi]

See this is one of the many reasons I hate car problems - I get a different answer from everyone! I guess if I knew more, that wouldn't be such a problem.

The spark plugs, wires, and distributor cap have been replaced, and didn't affect this problem. Air filter has been changed a few times and I've never noticed a difference in much of anything.

So it looks like it's the accelerator pump, fuel pump, and/or fuel filter. Any other opinions on which it might be?

I do have a gearhead friend, so I know I have someone who can help me out with doing whatever needs done.

 

[Pepsi90919]

i was gonna say throttle position sensor but then i noticed the year.