700r4 surging

[redneck_reed78]

When I am coasting in my 91 suburban, the engine surges, the rpms going up and down from about 1200 to 1400 rpm (I have a tach). The truck doesn't jerk around or anything but something isn't quite right. If I recall it seems to be more apparent in OD. Is this an early sign of the transmission on its way out since it has 226,000 original miles? (Not a transmission guy...) Because otherwise everything works great other than being tired. Or maybe TC because it likes to lock and unlock quite a bit (I think).

 

[VAL]

I had a similar problem with my 90, I thought I was the transmission also. It turned out to be if I remeber correctly, a temp sensor on the intake. Was causing the ecm to go crazy,

 

[redneck_reed78]

I had a similar problem with my 90, I thought I was the transmission also. It turned out to be if I remeber correctly, a temp sensor on the intake. Was causing the ecm to go crazy,

Could be something like that because my temp guage is a little bit goofy. I have a 180 thermostat but it takes about 30 minutes to get to the first mark which is about 155. Thats as high as it goes except one time when I had to replace the thermostat, it went a little over 210, so it only halfway works.

 

[1987 GMC Jimmy]

You're running TBI? They recommend a 195 stat so you can get into closed loop properly. That may help things out in general. Maybe check the TCC plug. When I got mine, it wasn't plugged in all the way, and it didn't feel right so I plugged it in correctly, and it got better. Have you changed the fluid and filter recently? It may be something worth doing if it's been changed before, which I'm assuming it has since it's lived so long. And maybe the TCC solenoid is no good since you say it locks and unlocks a lot.

 

[smoothandlow84]

Mine surged...after installing a new and performance built 700r4 and it ended up being a partially clogged fuel filter. I dropped both tanks only to discover fine silt in both. P.o. obviously didnt get a very clean fuel source, nor did he change the fuel filter in the tank or on the frame.