Hi,
I've got an 89 240 with the California emissions (EGR valve) package that is getting a 1-1-3 fault code. It runs rough at times and then will smooth out. If I clear the code, it stays good for a while but usually within a few miles the check engine light comes back on. This fault code indicates a problem with the fuel injectors. I've been running some injector cleaner in the hope that will help. I've listened to the individual injectors with a mechanic's stethoscope when it is rough they all seem to be firing. This leads me to think I have a dirty sensor but how do I figure out which it is? I've also read about checking the oxygen sensor in other posts. The intermittent nature of this makes it really tough to diagnose. It generally seems to run fairly well at highway speeds.

Any thoughts about what and how to check? How do I figure out which injector is bad if it is really an injector problem?

Thanks for any help!
Lyle