Mild bucking problem on '01 SSEi
 

My Bonneville currently has 107K. The bucking is most noticable with the cruise control set at highway speeds running about 1,800 rpm or so. When going up the incline of an overpass or hill, the car has a slight buck to it. RPM's never change. I have read on the forum that it can range anywhere from the MAF (changed twice in 3 years) to the TCC switch. I went out and tapped the MAF with no change in RPM. This leads me to the TCC. I have had problems with TCC's before in a couple of older FWD GM cars. Whenever they would start bucking, I would simply unplug the switch and deal with the unlocked situation of the TC and keep going down the road. Can I perform this same procedure on my Bonneville? I know that the TCC switch is located on the brake pedal assembly and wouldn't be very involved. Tomorrow afternoon, I will pull the TCC switch assembly loose and check it with a multimeter. I only plan on having this car for about another 3-4 months. My family is quickly out growing the Bonneville and if I can make it just long enough to trade it off, I'm going to. Thanks for any help you guys can give.

When was the last time you checked the plugs/wires/coils.

hey buddy

Check this out. https://www.gmforum.com/electrical-133/tcc-solenoid-switch-284972/ Adjusting it is just as easy as unplugging it.

I changed the plugs and wires at 90K but didn't mess with the coils. It now has 107K and the performance of the car couldn't be any better. It runs great except for the bucking issue. If the coils were starting to fail, would this cause a change in RPM's?

OK, so I followed the link to check the TCC switch and brake lamp switch. I've been on a business trip all week and just got back to check the car out. I metered both NO contacts and NC contacts with no issue. I even disassembled the TCC switch to make sure the contacts were beingeingaged. No problem there. I next went on the road test performing the 50 mph and lightly engaging the brake. RPM went up about 300-400 RPM. The strange thing, is that the RPM's never change while the bucking happens. I've heard that it could be possibly called "torque converter shudder". I don't quite know how accurate this is. I'll check the coils tomorrow afternoon. What should the Ohm;'s reading be and is there a +/- range? Thanks

Here's how you check your coils. https://www.gmforum.com/trouble-shooting-test-procedures-141/testing-coils-spark-plug-wires-278818/

You could also check on your motor mounts. If the engine can move you can feel that when your driving as a bit of a surge.

Thanks for the link! As for the mounts, I performed the solid mount conversion posted on here. Solid as a rock. I thought about my wording as for what is going on. The car isn't bucking hard enough to make you move around in your seat. It's more like a surging I guess. And it only happens when your at a constant speed applying light throttle to accelerate or when going up an incline. As soon as it starts happens, I can apply moderate throttle to WOT and the issue goes away.

Have you looked into what Bill suggested? I had a similar problem and it ended up being a bad spark plug wire that had got damaged from oil getting into it. I lived with the uphill issue you had, and only when the wires connectivity got worse did it causes a bigger misfire that I looked at the wires and plugs. My wires and plugs were only two years old and of high quality, but that didn't matter. The problem may be a easy one, consider replacing your wires- may sound off, but it fixed mine,

Go to Autozone and have them check for DTC's. A sporadic misfire could cause what you are experiencing, and could throw a code. If so, the DTC will lead you to the cylinder, and narrow down which coil/wire/plug could be the culprit.

I have a 2002 Bonneville with a problem very similair to "springcityssei", my shudder/stumble happens seemingly when it starts up an incline or when you are cruising at a constant speed (though not nearly always). It only happens for an instant. I have changed plug wires, the front ones were laying on the exhaust manifold, no help. Did the TCC on road test, worked fine. checked the coils with the following result at the plug wire terminals 5.4, 4.9, 4.9 at the the ICM terminals (back of coil listed in same order) 4.0, 4.5, 4.8 is this variance within acceptable limits?

It has another problem that may or may not be related. Starts fine when cold and usually when hot too, but sometimes will crank for 2 seconds start then chug for a couple seconds before running smooth. Occassionally it will actually die while chugging. Any thoughts would be appreciated. Thanks