93 lesabre - shudder and hesitation on acceleration

93 Lesabre 185,000 miles
smooth at idle
hesitates on acceleration with a shudder
replaced original fuel filter - no change
disconnected EGR - no change
pulled connector off each fuel injector one at a time resulting in slightly rough idle each time confirming injector is good
fuel pressure 41 key on
fuel pressure 34 at idle (read that 41-47 is optimal)
all vaccum lines checked and suspicious ones replaced - no change
vaccum line at fuel regulator pulled with slight engine idle change

The engine runs rough under any load whether slow or fast acceleration . with a shudder and hesitation.


Any thoughts??

tap on the injectors with something like a extention for 3/8 drive lightly while its running

I noticed you didn't check plugs, wires, and coils. Both my Lesabres had a good idle when I got them, but had a bad shudder under load. In both cases it was plugs/wires. If they are relatively new, try reseating the plug wires with new dielectric grease. It's also possible to get bad plugs or wires out of the box.

My 2c worth anyway.

A bad or disconnected air temp sensor can cause a lean condition, but sounds like an ign break down under load as mentioned.

Good spark from the coils
Is there a way to check if the coils are ok under load?
Plugs and wires replaced about 50,000 miles ago

Does the fuel pump pressure of 34psi seem too low?
hate to drop tank and replace the pump if it's OK
manual says 40-43

Just pulled the coil packs and all 3 tested within specs
all primaries tested at ~ 6.5k ohms
all secondaries tested at 0.5 ohms

will test wires and check plugs and if questionable will replace

If your gage is accurate the fp is low.

Check the MAF. Also pull off the EGR assembly, clean, reseal, and remount the tube from the intake plentum to the EGR base.

Update:

Replaced plugs & wires even though they still looked good (replaced 50K ago)
Still ran rough on acceleration
check each plug and discovered #3 plug not firing
previous coil pack check tested good - ohms within specs
checked coil pack to find that half of the coil pack was not firing (the other side to plus #6 fireing fine)
even though it fired well cold, once warmed up and under load it did not fire.
Replaced coil pack ($26 AutoZone) - Runs awesome!!!!

Hello CAMFLIGHTTRN,

I similar same symptoms with my 95 LeSabre all this week. The car was running fine, then suddenly we had a cold front pass through and the car started running poorly and would hesitate. I changed the plugs, wires, air filter and fuel filter about 20,000mi ago so I didn't think it would be any of these items. Nonetheless I pulled each plug wire off of each plug one at a time and tested spark on a spare spark plug. All 6 test appeared to produce proper spark.

Then I decided to pull the plug wires off of the ignition coils one by one. I noticed that when I did this, 4 of the 6 ignition coil studs produced very strong archs from the bare stud to various places on the ignition coil. However, the other 2 studs (from the 3-6 ignition coil) did not produce such sparks AT ALL. I concluded that this particular ignition coil was "weak". So I went to Autozone just as you did and purchased a Duralast ignition coil for $30 and good golly that solved the problem! I also tested this new coil with "naked studs" one at a time as described above, and this new coil also produced very strong archs.

So thank you for chiming back in and advising exactly what caused the problem you were having; it saved me alot of time and aggravation!!