1995 volvo glt 850 model year, 4.2 literes

Hi!

You meant a 2.4 litre engine, right?

Check:
- Fault codes from the diagnostics system.
- Fuel pump relay, located under the fuse box cover under the hood. If it's a green one labeled 103 it might be the culprit and should be replaced with the new and improved red one.
- The fuel pump itself, measure voltage to the fuel pump and make sure it's getting sufficient power. Can you hear the pump working when turning on ignition?
- Fuel filter might be clogged up. Located under car, by the right rear wheel.
- Unaccounted air entering through vacuum hoses. Spray them with start gas while the engine is idleing, if engine revs up you've found a leak.
- Throttle body might be in need of cleaning, probably a good idea anyway as it usually gives the engine a tad better performance.
- Mass airflow sensor might need replacement or cleaning of connector.
- If idle is rough check idle control valve.
- Make sure all plugs are firing, engine might be missing one cylinder, causing it to vibrate depending on engine RPM.
- Check that coil is ok.

Your problem doesn't sound like a camshaft/crankshaft position sensor, but you never know. Have the codes read, that'll probably help alot!

Well, that should give you some idea as to where to start checking...
Good luck mate!