03 lesabre shudders going up hill

I have an 03 lesabre and at 71k it just started shuddering while at a steady rpm and any size up hill grade. I first thought the plug wires were starting to leak out so I changed plugs and wires. I used Bosch wires and the oem delco plugs. It did not help at all. If I press the gas and the rpms climb then it will smooth up if I let off the gas it will smooth up. It will shudder at 35 just as well as 55 mph and it only does it while holding the gas pedal steady and the action of going up grade causes the engine to work harder. I looked around for broken vac lines and felt all the connections and they seem okay. I even tried an STP injector cleaner. NOTE all the plugs I changed looked very good. The old plug wires had elec burns on them. Also I noticed it will only shudder when the shifting is over and the rpm's drop when the torque con locks up.
Any idea's before I take it to the garage?

This can be caused by dirty injectors, low fuel pressure, a skewed o2 sensor, a bad coil, so there is no answer here without onsite diagnosis. A full scan will reveal any misfire codes and other inputs that may point to the source.

I have an 03 lesabre and at 71k it just started shuddering while at a steady rpm and any size up hill grade. I first thought the plug wires were starting to leak out so I changed plugs and wires. I used Bosch wires and the oem delco plugs. It did not help at all. If I press the gas and the rpms climb then it will smooth up if I let off the gas it will smooth up. It will shudder at 35 just as well as 55 mph and it only does it while holding the gas pedal steady and the action of going up grade causes the engine to work harder. I looked around for broken vac lines and felt all the connections and they seem okay. I even tried an STP injector cleaner. NOTE all the plugs I changed looked very good. The old plug wires had elec burns on them. Also I noticed it will only shudder when the shifting is over and the rpm's drop when the torque con locks up.
Any idea's before I take it to the garage?

At a steady throttle at lower rpms is when the mixture is hardest to fire. The electric load is the highest at that time so a slight breakdown somewhere can be noticeable.

If it were my 03 I'd take off each of the coils and measure the high voltage resistance and the low voltage resistance where the prongs plug in on the bottom. I'd inspect the bottom carefully and the the spark control module for corrosion. Reapply dielectric grease when reassembling. Then compare the readings for the resistances.

Take a look at the new wires in total darkness at the areas where the old wires showed the electrical burns you mentioned.

Usually this is engine related. But has the transmission fluid been changed? You're up to 71K. I go along with the group and change mine at 36K approx. It takes 7 quarts and I installed Dextron VI fluid from Walmart brand on the last change. It's a new and improved fluid with GM's new standards. A remote possibility might be the clutch for the torque converter slipping as it's clamping down to 99% lockup. There's a controller valve that varies that lockup for engine load and conditions. allowing lockup from 99% and lower.

If it were my 03 I'd take off each of the coils and measure the high voltage resistance and the low voltage resistance where the prongs plug in on the bottom. I'd inspect the bottom carefully and the the spark control module for corrosion. Reapply dielectric grease when reassembling. Then compare the readings for the resistances.


I did remove the coils a while back to inspect for cracks. I noticed the aluminum top of the module was all corroded white. Is this supposed to be cleaned and dielectric grease smeared between the module and the coil?

Something I forgot was the #4 injector wire was damaged at one time and they repaired it by splicing the wires back together with an awfull looking nylon covered crimp. Would this show a code if the circuit was not complete? If not, can you replace the injector electric plug on the harness? Do they sell the plug and two terminals? I have a duetz plug crimping tool and kit if they are near the same style crimp plier.

Also the trans oil has been changed/flushed at the dealer two times since new. They claim to get all the oil with this type of flush as they hook up a pump system. I did check the trans oil today and it is very clean.

What do you mean by misfire codes?
I am experiencing some of the same symptoms. My "check engine" light has not come on. What is known of the scanners that Auto-zone sells? Will they do more than the vehicle's internal tester?

If you check everything and don't find the problem, shell out some cash and replace the injectors or send them out to get cleaned. My car does the exact same thing and it's the injectors. Dirty injectors don't show up when you run a diagnostics test cuz they're still working, just clogged. I tried everything to clean my injectors out but they were just too bad. Instead of sending them out to get cleaned I just replaced em. I only paid about $42 a piece. Well I've only replaced 3 so far (due to shortage of funds) but I still know it's the injectors. They're re-mans but it doesn't matter cuz I'm gonna put a bigger motor in my car anyway and sell the one that's in it now

Well I found the answer. I took the car to the dealer that sold it to me (used) and said fix it. They called me back and advised the torque converter and the torque converter valve needs replaced. $550 for the TC $65 for the valve and $600 labor. While she totaled it all up and i'm starting to get worried the service writer explained that the used car 100K warranty will take care of it and I had a $100 deductable. What kind of luck is that? I never had something go that smooth before.

ok im gonna throw this out there... i thought i had a tranny shudder as well and after looking around and wasting time and money, i finally found out that the front engine mount(torque strut) was bad and it felt like a shudder while in high gear. it was the twisting of the engine in the mounts. check it out.:banghead: the action i could feel back through the throttle as well, i guess it was pulling at the cables

Solution?

I fixed it but I am not certain how. I decided to go through the front end because I really haven't done much to it for years.

I replaced axles, shock struts, sway bar bushings, one caliper and one rotor and brake pads and plug wires and spark plugs. I did the basic compression checks.
I don't know if I needed the shocks but I got two new for $25. I also don't know if I needed both axles but they we only $39. each; Bosch plug wires we $17. and AC-Delco plus were about $2.50. Note on plugs, I recently got stung by a resister plug which was a replacement size. I spent two day trying to figure out a problem and found the resister, while have the same ohm value, did not work -- strange but true.

I drove 500 miles to Cleveland and back; got 26 mpg and not one shudder.

I set the camber with a level and I think I didn't have enough negative camber and I'll fix that when I can get some alignment specs.

I feel that one axle and one plug wire might have been the culprits but I ain't in a laboratory.

Thanks