Slight Hesitation or Bucking when going uphill

[DelCoch]

I did a search and couldn’t find anything similar to this.

I have a 95 Jimmy SUV 4x4, V-6, and I recently started getting a slight intermittent hesitation, or slight bucking when going up hills. (At highway speeds of 60-70) It’s most noticeable when running on cruise control. It will do it 3-4 times and then it will shift out of overdrive and will be fine. Also, if I press on the gas pedal it will shift out of overdrive and run fine. It runs and idles fine otherwise, and the tach doesn’t show a drop in rpm’s as this happens, so I’m thinking it might be related to the transmission. I have about 50K on a dealer-rebuilt transmission. My brother has a 92 Buick with a V-6 (front wheel drive) which has started doing the same thing.

Most of the time, but not every time, the SES light will blink about 4-5 times and then go out. I went to Auto Zone and had the engine code read, but no codes were listed.

I did a tune up, cap, rotor, plugs, wires, ran Techron and the other popular additive through 2-tanks of gas, and a new transmission filter – no help.

Has anyone else experienced this? Any ideas of what is going on?

DelC

[demotim00]

I would say since the SES light blinks while it acts up I would recommend spending the money to have a diagnostic ran at a shop, as they tend to show more codes and are more reliable than having it checked at places like Autozone. As far as ideas on whats wrong, the only thing I can think of off the top of my head would be a problem with the Transmission, however as always, mutliple items could be the problem.

[DelCoch]

I was thinking transmission also, but my brothers Buick, which is front wheel drive, is having the same problem, and the only thing close the two vehicles have in common is the V-6 engine, and even those are different.

Thanks for the reply,

DelC

[BlazerLT]

Originally Posted by DelCoch

I was thinking transmission also, but my brothers Buick, which is front wheel drive, is having the same problem, and the only thing close the two vehicles have in common is the V-6 engine, and even those are different.

Thanks for the reply,

DelC

You need to replace your fuel filter and check you CPI and nut kit for leaking.

[DelCoch]

Originally Posted by BlazerLT

You need to replace your fuel filter and check you CPI and nut kit for leaking.

Fuel filter was replaced when I did the tune up, forgot to add it to the list. I'll check the CPI.

Thanks for the reply,

DelC

[94 Jimmy]

Del
I seem to be harping on this, but most of us don't change the O2 sensors nearly often enough. These things can go a little bad, not set any codes and cause a lot of strange problems. If you haven't changed it in over 50KMi just do it.
My sensor drifted to a rich reading, this caused the computer to lean the mixture slightly. On sweeping right turns while accelerating, like freeway onramps, the engine would lean out and quit. Great fun, lose steering, brakes and power all at once with someone behind you with his foot to the floor looking over his sholder for oncoming traffic. Your problem could be a bad mixture causing hesitation only at sustained high throttle settings.
I have an OBDII decoder, and with my laptop I saw that the sensor was spending most of its time in the rich range, the cheapest, easiest fix was the sensor, I tried it and problem gone.
I have a 94, bet you could tell from my logon. I only have one sensor, you apparently have three. The one behind the cat is only to check if the cat is working. So your choice is the one in the maniford or infront of the cat. You could replaced one and move it around until it fixes the problem, or just drop the $90 bucks and replace both, it's not much of a job.
You could also invest in an OBDII decoder and read all of your sensors real time, their under $100 from Scantool.net and are a real help in diagnosing intermittent problems.
Let us know what you find.
Hope this helps, see ya.
94