Seems to be missing but passes ballance tst?

[50atheart]

I have an 89 5.0 with MAS air, CA smog, AOD (E?) Cold air and no major mods.
My problem is that I have what sounds and feels like a missing cylinder or two when I am at low RPM's and under load. I am not pulling any fault codes at all, and it passes the cylinder balance test as well. It idles good and rev's good too.
Does anyone have an idea what to look at/for? thks

 

[BlownFiveLiter]

It could be missing under a load, but pass the cylinder balance test when there's no load on the engine. How recently have you replaced all of the major tune-up items (plugs, wires, cap & rotor, PCV, fuel filter, air filter)? If it's been a long while, or you can't recall it having been done, those would definitely be some good places to start. How do the plugs look? Any partial fouling of any plugs? You could also do a compression test, if the tune-up had already been performed recently and this problem still existed afterward.

 

[50atheart]

Thks. I will go back thru the basics completely. Plugs (copper), wires, rotor, cap, replaced 2 months ago. fyi. I'll check compression. There is a smell of raw gas at the exhaust as well.

 

[50atheart]

solved

The problem turned out to be that the cat was flaking apart and plugging up the inside of the muffler.