91 lesabre bucking

i have a 91 lesabre and its bucking. fuel filter was changed 1 week ago and still the same prob any suggestions out there?

Be more specific. Bucking how? when? What rpm ranges?

i have a 91 lesabre and its bucking. fuel filter was changed 1 week ago and still the same prob any suggestions out there?when at idle, the rpms go up and down and when its in gear it goes way down almost to the point of stalling. i can't tell you exactly what # rpms because i have no guage. some suggestion were to change wires and plugs, ign coil, and o2 sens. this has all been done about a yr ago. the fuel filter was changed about 2 weeks noew but, my service engine light has been on since last summer
it came to be a code 41 and i changed the cam sensor ttwice.
me and a friend of mine also came to the conclusion that the code 41 also included the magnet on the large gear on thwe timing chain do you think that this could be the problem? it's getting worse everyday i'm afraid it will stop running soon.

My cam sensor magnet came flyin' off the cam sprocket at about 180k on my '91 when I gunned the engine on the interstate to pass someone... instant check-engine light :)

Only symptoms were the check engine light, and occasionally when accelerating gently from a stop it would buck a small amount - but rarely. Take the cam sensor out and look through the hole while turning the engine with a wrench. The magnet normally protrudes from the sprocket.

Replacing the magnet involves removal of the timing set (sprockets and chain). On my '91, there is one LARGE bolt holding the cam sprocket in - and the torque spec for mine was 75 ft-lbs plus 90 degrees. Ouch! Trick is to hold the sprocket still while putting that kind of insane torque on the bolt. I chose not to use the chain to hold the sprocket still (worried about stretching it - think 2" diameter, 75lbs = 450 lbs of tension, BEFORE the 90 degrees!), and had to rig up some stuff to hold the thing still...

Not being a seasoned mechanic, doing the cam magnet myself was a LOT of work.

As far as the engine stalling - when mine was doing that (a little bit), the problem was carbon buildup in the throttle body. I just took some towels, an old toothbrush, and some solvent and went at it. Just don't stick anything down the smaller passageway for the MAF sensor - it is very fragile.

Another possibility for engine stalling like that is a defective IAC motor - it is a stepper motor mounted just below the throttle body, 4-wire connector. Careful with the IAC though (it is possible to damage it on re-installation if the plunger is extended out too far, and if you turn on the ignition with the IAC removed, it will "launch" the plunger...).

Had a couple more questions that might help narrow the problem with the rpms up-down:

1 - does it just do it at idle, or at all speeds?
2 - is it rhythmic, or erratic?
3 - does it do it when the engine is first started, or when warmed up, or both?
4 - have you checked for leaking vacuum hoses?
5 - have you re-checked the ECM for more codes set other than the code 41?

Had a couple more questions that might help narrow the problem with the rpms up-down:

1 - does it just do it at idle, or at all speeds?
2 - is it rhythmic, or erratic?
3 - does it do it when the engine is first started, or when warmed up, or both?
4 - have you checked for leaking vacuum hoses?
5 - have you re-checked the ECM for more codes set other than the code 41?

hey thanks,that's exactly how the check engine light came on! (i gunned it to pass someone). In relation to ur ?'s 1-yes at all speeds and especially in overdrive! 2- it is rhymic. 3-both. 4-no. 5-no

Try replacing the wires with Delco parts and see what happens,or maybey a bad tank of gas.

hey thanks,that's exactly how the check engine light came on! (i gunned it to pass someone). In relation to ur ?'s 1-yes at all speeds and especially in overdrive! 2- it is rhymic. 3-both. 4-no. 5-no

A few thoughts -

1 - yes, try the Delco plug wires. I have also used UltraSpark from Autozone with good success - seem like good quality wires, although the metal clip tends to come off once they are a couple years old.
2 - make sure it is running on all 6 cylinders.
- check for spark (I usually just use a timing light to check each wire)
- maybe have the injectors cleaned (these are not those pesky Multec's - they are bosch injectors, on my '91 anyhow)
- check resistances on injectors and make sure they are all consistent (somewhere in the 10 ohm to 60 ohm range, don't remember exactly)
- check resistances on the three coils in the coil pack, just to make sure (measure between pairs of spark plug wire terminals w/ ignition OFF), making sure they are consistent (somewhere in the 5K ohm - 20K ohm range, don't remember it exactly)
- if you have access to the equipment, maybe try doing a vacuum gauge test and a compression test (a Haynes manual will show how to do it).
3 - if you have spark, and the rhythmic RPM change is not in sync with the flashing of the timing light, and are not in sync with every 2nd flash of the timing light, then:
- if the up/down is in sync with about every 3rd flash of the timing light, maybe it is your timing chain. This is a wild guess, but when I was repairing my cam magnet issue it was obvious that the magnet had gotten caught in the timing chain and gotten crushed by it (the magnet was stuck to the engine block, and was *much* smaller than it should have been - and about the right shape to fit in a tooth in the chain). My chain was in very good shape though, and I had driven the car 2000 miles after the cam sensor code was set (was on a long road trip).