1994 4.0 automatic, When put in gear it starts bouncing back and forth from 400 rpms to 700

[clapped4.0]

Anyone know why it does this? It just revs back and forth.

 

[rumblecloud]

Could be a few things.
Have you pulled any codes yet?

Vacuum leak
O2 Sensors
MAF sensor
And more...

Normal RPM should be anywhere from 8- 1000rpm at idle Higher at cold start-up, then down as it warms. Have you performed any maintenance prior to this happening?
What's the mileage?
Does the rpm continue to rise and fall when it's warmed up?

A cheapo OBD1 code reader from a local auto parts store could offer some clues as to what might be causing it.

Please post back with more info so we can help.

 

[clapped4.0]

only codes are for transmission 3/4 shift solenoid and torque converter clutch circuit fault. Looked for vacuum leaks and found 1 which was causing a 1500 rpm idle. replaced MAF sensor. Haven't checked o2 sensors. Previous owner had done spark plugs and coils just before I bought it and I haven't driven it much since i bought it. 210,000 miles. It seems to do it more when warmed up.

 

[clapped4.0]

Also anyone know where to find tcc solenoid at? a4ld trans, tried everywhere I could think of but not finding any.