89 lesabre missing during accel and steady speeds

Hi, new to the forum. my name is jake. I love this car and it has not gave me any real problems for 2 years until now. When i drive this car (hot or cold) during acceleration and steady speeds the car will miss and shudder back and forth a little bit. im stumped plz help. have already done the following

-fuel filter
-plugs/wires
-swapped ignition coil 4 one in the junkyard thinking maybe mine was bad. didnt help
-cleaned throttle body
-changed all fluids religiously

maybe a vaccuum leak, spark plug gap, fuel delivery problem (the pump has always been loud but lately its getting louder and sumtimes it will go from loud to silent and the car almost dies. and the pump used to prime for a few seconds. the past couple months it hasnt been priming, but still starts rite up) . i dont know. any ides are appreciated.

Welcome to AF. Try testing the fuel pressure for starters, your description can be caused by the trans slipping or shuddering also, only a road test by a competent tech can pinpoint the problem.

i had a 87 park avenue i put plugs and wires on it was doing about same thing your saying. i'm sure you got the 3.8 right? well took it to good year had it put on a machine and said ground wire braking down some where but they never could find out because had it on there twice and run good on machine. anyway i figured it out on this site it was the dam module.

ya its a 3800. it usually only does this during light throttle. if the gas is to the floor or somtething it wont hesitate and miss.

Have you checked for codes?

Sounds like a bad ICM or weak pump.

The ICM is the part that sits directly under the coil pack. It takes 3x 11mm nuts and the wire harness to remove. These can be tested for free at most parts stores but they need to be warm or else they may pass as good even if there is a fault.

That would be free to at least check it.

Otherwise, check fuel pressure via screwing a gauge onto the valve on the fuel rail. You should have about 40 PSI at idle. Significantly lower and you have a weak and dying pump.