We have a 94 850 wagon non turbo and we can't figure out what is wrong with it. It isn't throwing any codes but is reluctant to start and idles at about 2k. It normally idles at about 1k but lately it has been all over the place. It revs up on its own and bogs down and dies when you put it in gear. We changed the MAF, the plugs and plug wires and the fuel filter. I've read all the articles here that relate to this problem but none of the listed culprits have been our problem. We haven't checked the cam position sensor yet. I've also read it could be the ignition module. It has around 40lbs of fuel pressure and the relay is working fine. I bought this car to be my sons first car and hes really losing hope in this car running. We really have no idea what is wrong with it and can't fully explain the issue because we don't know what else to check. It started fine the other day and idled right around 1100 but it started revving up around to around 2300 all on its own for a few minutes then it would just drop back down to below 1000 and quickly rise up to 1100 and stay there. It would rise up again for a few minutes and then just drop back to normal without us doing anything. We drove it around and revved the hell out of it and it didn't have any issues. We are going to drive it daily and see what it does and go from there. It started and idled fine the other day but today it refused to fire up. We know it isn't the cold because we've driven it at low temperatures before. If it narrows down any possibilities or theories the car was built in 12/93. Does anyone know what else to and why it revs on its own?

 

I would read the codes on the system. Coolant temp sensor and intake leak come to mind.

 

If you are not getting any codes, inspect the vacuum lines and intake boot for cracks - try spraying some carb cleaner along seams to see if any sucks in while the engine is running (if it bumps the idle that a sign some got sucked in). You may also want to inspect the intake by removing the MAF and idle air valve for any dirt or gunk - if you decide to clean, use CRC MAF cleaner as carb cleaner can be too harsh for the grid wires in the MAF. After that, you may want to try replacing the temp sensor as Robert noted...

 

As mt6127 said check vacuum hoses(ALL of them). A year ago, My car will stall at idle when my brake was engaged at stops and idle when park. The issue was the vacuum line that goes to the brake booster. It is often missed because it goes under the air filter box in the back firewall on the driver side. You can trace it from the intake manifold under the throttle, snakes under the airbox to the back of the car. Just one place to check and a cheap easy fix for me. Just 12$ worth of vacuum hoses(5/16 diameter in think) that stop stalling for me.