It is a 95 with a earlier engine. I'm in Knoxville, outside temp doesnt seem to matter. This miss is worse when the engine is warm, but still hesitates obviously when cold. Last time I drove it, it was acting worse when cold.

Haven't had it out lately since the window went off track and both headlights started making a noise like the gears are stripped. Was driving it all the time before this.

All this happened after I replaced the clutch (throw out bearing broke due to wear on the fork). Wish I knew how to test the O2's positively.

 

All y'all need to let this old OLD thread die and start your own.

 

Way better and more helpful to keep all of this fairly similar info in one thread IMO.

I have the same problem - runs great open loop (cold), as soon as it hits that magic temp, blech. Skips, stumbles, misses. If I open the throttle it will even out after a few seconds (of course by then my wheels are spinning and/or I'm going 60mph). Idle is generally fine, and off-idle is fine under no load or when just pulling away slowly about half the time. But 1000 - 2000 rpm is yuck town. It's like it's running on 3 cylinders. I'm guessing it's rich, which could be leaky injectors or else misfire?

Mine is a swapped 97 LT1 from a firebird (into a 1966 C10). I replaced Opti, water pump, plugs, etc. I am running the 2ndry O2s as Primary (long tubes, those wires/connectors were closer and that style plug is more common - I rewired the PCM harness). The O2 sensors look fine, but I guess I'll replace them anyway. I just unearthed a Winders laptop so I can try Autotap tomorrow. Hope to get some obviously jenked readings that point to something I can easily (and cheaply!) fix.

 

The first thing to look at is the temp sensor in the water pump. This tells the PCM whether the engine is cold or hot. If the PCM thinks the engine is cold it will enrichen the mixture. If it's wrong and the engine is actually warm it will be running rich.

A leaky injector is always leaky...you would have an extended cranking period starting cold as it would let the fuel pressure drop when the fuel pump is off.

A computer scan would help a lot. Good luck getting that laptop going!

 

My computer scan was not so helpful. Apparently my scan s/w doesn't "See" that many variables on an LT1. I do have a lean Bank 1 code, which makes sense and narrows it down to that side. If I disconnect both O2s, the motor runs nicely. So it is only running crappy in closed loop. Also narrows it down. Seems like a misfire. In closed loop it spits soot out driver's side. So possibly bad spark. I'm going to replace the plug wires and see what happens. Luckily the driver's side is the issue and those wires are way easier to get at (stupid accessory bracket).

 

You have a lean condition and soot on the same bank....could you have an exhaust leak fooling the PCM into thinking it's running lean and enriching that side? Check that first, then move to plugs....read 'em before replacing

Don't replace just one side of wires...they're all the same age so the issues are the same everywhere.....