Hesitation/Bucking

I have searched the web and this forum with little success. I have a '98 Riv with 145,000 miles. Last winter is started bucking/hesitating. There is no rhyme or reason as to when it will do it. Flat road. Uphill. Downhill. Cold weather. Hot weather. Damp. Dry. It makes no difference. It will do it every day, but not every time I drive it throughout the day. I spend all my time behind the wheel just waiting for it to buck.

Here is what I have done:

New wires
New plugs
New coils
New ICM (twice - one was a used OEM one)

The Check Engine Light has NEVER come on.
Regardless of the CEL, I have checked for codes and there are none.

I cannot throw any more money at it and now I just hate driving it. POS.

Any ideas?

I know you say the CEL has never come on, but does it flash while the car is bucking?

matt270avian wrote:

I know you say the CEL has never come on, but does it flash while the car is bucking?

Isn't that the same as "coming on"?

Abaddon wrote:

matt270avian wrote:

I know you say the CEL has never come on, but does it flash while the car is bucking?

Isn't that the same as "coming on"?

Sort of. He might be thinking to look for a solid light at all times, where as I'm talking about it just flashing during the bucking. He might not think/know to look for that.

Never looked but I will next time.

Can you scan? I am wondering what your timing looks like during the bucking.

youve got a 98. Get a droid device from friend or family if you dont have your own and torque app with bluetooh OBDII  ($20 investment?) and start seeing what is actually happening with your car.

I would have someone scan and check MAF sensor signal. It can cause your issue, and doesn't always set an SES lamp. If the intake air temp (IAT) sensor in the airbox has failed, if can cause similar issues, but this is not common unless you've been working near the intake. Good luck.

Update..... I have been noticing for a few months that the transmission will often shift hard/harshly. Sometimes it would shift fine, other times it would hit like a sledge hammer. And it was doing it today. So I put some additive in the trans (siphoned some fluid out first so as not to overfill it). And since then it has not bucked once! I never noticed it bucking on the highway, just around town. So maybe it was bouncing between gears due to a sticky valve or solenoid or something as it was still at the speed where it would HAVE to shift up and down, unlike on the highway. I also noticed that it would almost never come out of OD on its own when lugging up an incline. I would have to let off the gas and then get back into it for it to drop down to third gear. Today I noticed a couple occasions where it hopped back out of OD on its own. So I will keep you apprised.

For those members here that don't know my 69 Riviera transmission issues... this is sooooo typical!

Could this be signs of the torque converter clutch going?

matt270avian wrote:

Could this be signs of the torque converter clutch going?

Converter lockup in low gear, yes. Chances are, there's a code for it stored in the PCM. It won't turn the SES light on until it's locked up permanently.

Not likely. He said "I never noticed it bucking on the highway, just around town."

I've had the experience of TCC failing, and it is something you notice cruising on the highway.

AA wrote:

Not likely. He said "I never noticed it bucking on the highway, just around town."

I've had the experience of TCC failing, and it is something you notice cruising on the highway.

It bucks like an effin bronco at normal road speeds if it locks up. On the freeway, it's BARELY noticeable. You or I may know something is wrong because of all the tuning experiments and what-not, but most people wouldn't think twice about it until they got under 55mph....

Okay. Can we agre 55 mph is more "highway" than "around town"? The TCC doesn't even lock until 3rd gear. You're right, my TCC tuning was not stock, but I noticed it right away as a pulsation above 60 mph when it started failing. Turning on cruse control made it most noticeable.

I don't think this is his problem, but maybe?

For what it's worth, I had a clog in the valve body once, after AAMCO installed my rebuilt trans. The result was inability to shift into 1st gear, which caused the car to stall every time, bucking wildly as this happened. Not saying yours is the same, but a misbehaving valve body could cause the behavior you're describing.

AA wrote:

Okay. Can we agre 55 mph is more "highway" than "around town"? The TCC doesn't even lock until 3rd gear. You're right, my TCC tuning was not stock, but I noticed it right away as a pulsation above 60 mph when it started failing. Turning on cruse control made it most noticeable.

To be fair, I think you're assuming the bucking will be EXACTLY the same between cars. Not sure if this would always be the case.

TCC lock-up is controlled electronically, and will only engage in 3rd or 4th gears above a specific speed at certain throttle %. That much is the same between all cars, and could reveal if this is TCC related.

Yardley, use one of these tests to rule out TCC as the fault

1) drive below 28 mph. If the bucking happens below this speed, it isn't the TCC.
2) push and hold the throttle about 1/3 while cruising at 35 mph. If the bucking happens under this condition, it isn't the TCC.
3) push and hold the throttle about 1/2 while cruising at 50-60 mph. If the bucking happens under this condition, it isn't the TCC.
4) if the bucking happens at any time under WOT, it isn't the TCC

Thanks guys. Been flawless since I put the additive in yesterday. Drives very smoothly.