So ever since I got my 88 l98 back in 05 it has always ran ok but never as good as i thought it should. But over the past few years it began running more and more rich along with very sporadic idling all the time. I've always been trying to correct the issue by going through every sensor, wire, injector, and vacuum line, and anything else that could possibly cause it. I got an adal cable to datalog last summer but never got it working well until a few ago when I started playing with it again. I finally got it to connect with TTS datamaster (which is a damn awesome program) and noticed some very weird things happening, injectors pulsing way too much, coolant temp sensor would only read correctly every once it a while, among other things. So after some searching on thirdgen and some datalog comparisons with my 87 lb9 (which has always ran great) I figured I would try switching the ecu from the 87 into the 88 and sure enough, eureka! the 88 has ran awesome since I swapped the ecu's, no more cloud of rich smoke from the exhaust and a nice constant and consistent idle at 750 every time. car also runs better and better every time since the rings are no longer being washed out with fuel. so pretty much about 5 years of headeache and frustration was fixed with about 15 minutes of work and about 6 little bolts

So in conclusion, I always see lots of people on here with the similar running rich/idle problems and my advice is to save yourself the headache and look at your ecu/prom first because you might get lucky like I did and just have a simple fix.

 

I have like a dozen of those 165 ECM's laying around for that very reason. I'm amazing how unreliable they are after they get old.