Bucking

[alaska_guy]

Based off your symptoms I am 90% sure it's the boost valve. Really not much else that would cause the bucking you describe. Call a good transmission shop locally and ask them if it sounds like your issue with your symptoms to confirm.

 

[Danneman]

Ok - Thanks, I will make this part of my agenda at my next garage visit. Looks like it's part of the overall "Functional Test" outlined in the service manual so I'll just have the whole thing done.

Meanwhile, I found a table in the service manual that outlines the typical values a scan tool would show for Transmission Data when warm and idle - and the only difference between these expected values and my actual values was that the 3-2 Downshift Solenoid was showing as Off and apparently should typically read On. I wonder what should be made of that?

Also noticed that this table in the service manual shows four data points that my scanner isn't showing: "Current TAP Cell", "Maximum TAP", "1-2, 2-3 TAP Cells (4-16)", and "TAP % of TP".

 

[Danneman]

Ok, so take a look at what I stumbled upon in the 1998 C/K service manual: apparently what I'm experiencing, GM calls a "chuggle" as per their shift condition descriptions. Found this on page 7-233 (in the volume 4). It doesn't seem to go on to talk about any testing procedures specific to a complaint of transmission "chuggling," but as this trans is under warranty with my dealer (was replaced about 1.5 years ago) I'm expecting them to get to the bottom of it.

If nothing else, I feel a great relief that my condition is recognized in the official service literature and has a name (that I would never have thought of). I'm dropping all other "theories" until this one is pursued further.

 

[Danneman]

Update. Not a transmission issue. Rather, I'm getting misfires on cylinder 7 under load.

I can see them being registered on my Tech 2 while experiencing the issue - normally the value shows "0" for each cylinder, but then as the misifre happens it shows the count and then when they stop it sets it back to 0.

We swapped the plugs and wires with another cylinder but the misfire stayed on 7. Found a little corrosion in the distributor so replaced the cap and rotor again but that didn't help. Cleaned the fuel injectors in all the ways that can be cleaned, several times, and even did top engine cleaning - hasn't helped. Best guess at the moment is bad fuel injector - which is irritating because I had just put a new spider in about two years ago and neither the part nor the labor were cheap.