puzzled... occasional bucking at 45-50mph

Hi all,

Having an occasional glitch with my '91, and was wondering if anyone else here has seen similar problems and was able to figure out what the problem was & fix it... (posted once before but have better info now)

My 'sabre is occasionally very harshly "bucking" - it feels much harsher than just an engine miss, but not entirely sure. More like a really hard shift, but it isn't during a shift or TCC apply. It's like something is binding or locking for a split-second. Car has 212k miles on it and otherwise runs really well.

Some things I've figured so far:
- Tranny is 440-T4 / 4T60; engine 3800 VIN 'C'
- No codes are being set.
- Problem happens only in the 45-50mph range in 4th with the TCC applied
- It seems to happen mainly in cold weather in the first 10 min. of operation
- It happens seemingly only with the engine under some load (like uphill)
- Because of another issue I recently dealt with, I can rule out the ECM, Ignition module, and crank sensor.
- The valve body and ECM do not appear to be commanding any shifts or TCC apply/release when this happens (nothing indicated in the tranny gear indicator switches or TCC apply wiring).

Any ideas?

Any ideas?[/QUOTE]

I replaced my plugs and wires and got rid of the same problem...( had a bad wire)

Thanks! I will try putting a new set of AC Delco wires on it. The plugs are only a couple of months old (AC Delco standard plugs), and the wires aren't that old either (approx. a year I think), but it's worth a try... Wouldn't it be funny if just a set of ignition wires solves it after all this head-scratching :)

Yep. Got a bad plug wire. Whether or not it was the actual cause of the problem I was having (I hope it was!) will take a few days or weeks to determine, since it is warm here today.

http://files.automotiveforums.com/gallery/watermark.php?file=503/277136plugwire.jpg

This is a picture of the top of the spark plug boot of an Autozone "Double Silicone" wire that is about a year and a half old. Never had one do this to me before....

I suppose weak ignition has worse consequences in cold weather?

- GB

Check out other threads and you will see why most people that own GM autos recommend AC Delco parts.