Hello and Merry 2025 Christmas! I picked up a ’94 850 which starts (with a little help), will not idle at first but after warming up idles, but surges between about 1000-2200 RPM. While driving the car above 40 MPH the surge is not noticeable but below that it wants to drive along at about 35 MPH without my foot on the accelerator. It looks like the TPS was already changed out but not positive (found and old one in a box in the glove compartment). I haven’t put a scanner on it yet due to outside temps below 0F. If it gets above 10F I’ll put that on it.

Any ideas? Thanks all. fpak

 

the 93-95 850s are "OBD 1" so your scanner won't work. To check for codes, use the diagnostics box under the hood (front of the engine towards the passenger side. Google for how to jumper and read the codes from the LED. My sense is you probably have an intake air leak - start by checking the vacuum "tree" by removing the throttle cable spool cover. look for cracked/torn hoses or tree stems that don't have a hose or a cap. Next I'd check the engine coolant temp sensor. You will find that at the thermostat cover (follow the upper hose to the block). You can unclip the harness and measure resistance. Google for a resistance chart but you'll want to see what it shows for both a cold and a warm engine. After that, inspect the intake air hoses - you can also spray around with some carb cleaner on the intake air hoses and around the injectors for possible air leaks. Last thing - do a stage 0 tune. Pop the wiring cover and look for date codes on the spark plug wires. 5 years is too old. If its not been done recently, go cap/rotor/wires/plugs. Use OEM copper core plugs with a correct gap (.028 if I recall).

 

And by the way, the '94 850s did not normally have TPMS, and this would have nothing to do with your idle problems.