So this could be the issue causing the miss?
Still confused on why it would run fine on base timing if it was a motor issue. Unless it not sealing so messing with the sensors?
Thanks for the reply, I'm just figuring out responding and using the forum. It's a 94' Chevy C1500, 4.3 V6, automatic.
Started out a year ago with hard starting when cold(Not really cold at 60 deg. at the lowest.
It progressed to lackluster accelleration in the midrange to falling on it's face during anything other than moderate pedal into it.
Changed the basics(Plugs/Cap/Rotor) with no change.
Plugs looked good BUT number 1 was almost too easy to remove. Loose in my mind.
No good results or changes.
Then I pulled out the parts cannon.
IAC, TPS, MAP, Temp sensors, EGR, O2 sensor, pigtails for all with the exception of the IAC.
2 years ago, rebuilt the TBI with new injectors just to do it. Overmaintain it.
The IAC...
If I unplug it while idling, nothing changes by even a hair.
The resistance measured on the bench is 52-54 ohms.
Never checked the pigtails going to the new IAC. for power/resistance or however you check it.
Changed the Distributor. No start. Crappy distributor now I found out the hard way (A junk Amazon "MOSTPLUS" brand).
No start, I had to change the ignition module from the get go to get it to start.
Had the shroud off as well as the fan to easily get into the engine bay.
I could time it at that time because the timing mark wasn't crowded with the fan or shroud in the way.
FYI, the truck won't overheat in 65 deg. weather without the fan installed which seems odd.
It closes loop at 195 when the thermostat opens and never got hot unless it's 90 deg. out with the AC on at a stop light with the fan/shroud installed.
I check temps with infrared temp gun on the thermostat housing as well as the instrument on the dash.
With the ignition advance wire unplugged I kind of got it TDC zero deg. advance.
Timing mark jumping around and never steady.
This is why I say "kind of" hit 0 deg. advance.
It's not idling consistent and missing so it's not steady by a long shot.
Changed the rotor for the 4th time in 3 months and the cap is #3 just to be certain.
Another thing;
I had an IAC. code a couple of years ago and changed it.
Solved the code issue.
Changed it again when it started running bad.
I'll check fuel pressure(filter is 2 month old and the one before that was a year ago).
No fuel leaks or smell.
Fuel pump in the tank is 10+ years old.
Never checked compression because plugs are always dead even light brown.
I change the Plugs/wires/cap/rotor every season.
I gap the plugs at .035 per Factory specs.
All ACDELCO maintenance parts.
I'm on timing light #2 just to confirm it's not the light missing the mark.
Forgot;
It idles and starts better with the ignition advance wire unplugged.
Still a miss at idle and it's inconsistent not on the same beat.
Exhaust is rich.
I removed the Cat a long time ago.
This was a long reply but everytime I look at that old boy, I remember it running 100% top notch just back in Feb!
I mean top notch.
Thanks for reading all of this!!!
Pete.