Hi,

I have an '89 245 that rough idles and hesitates only when warm. I've done the following:

- Verified that all ground, hose and cable connections are OK
- Replaced air intake hose to fix vacuum leak
- Cleaned throttle body and air bypass valve
- Checked plugs, cap and wires -- everthing OK
- Replaced blade-fuse
- Replaced RPM sensor
- Replaced engine coolant temp sensor
- Replaced thermostat
- Ran a "quality" injector cleaner through one tank of gas
- Visually inspected the AMM (clean inside and wires are intact) and fuel pump relay (i.e. I opened the relay -- don't see any broken solder...looks almost new actually, so I think it may have been replaced by previous owner)

The car certainly starts up and runs better than it did before these repairs, but the warm stalling/hesitation problem still persists. Here are my questions:

1)How can I tell if the problem is due to too lean or too rich a mixture?
2)Should I check the resistance/voltage on the AMM & fuel pump relay? If so, how?
3)Haven't yet changed the fuel filter (probably overdue for this), but why would this solve a problem that occurs only when engine is warm?

Any advice would be greatly appreciated. It's great to finally be learning how to fix my car (I'm new to both volvos and auto repair), but I'm incredibly frustrated at this point. Thanks.

- Mark