Victim: '87 IROC L98 w/100k and stock except cat-back.

Initial Events Leading Up To Death Of Car: Replaced leaking valve seals and intake manifold gasket. In the process, also needed to replace coil, ignition module, cap/rotor, pickup coil. New fel-pro's all round on re-assembly and new intake bolts. Also did not re-install A/C compressor and lines as was not working anyway. Valve lash set six times as two lifters took a long time to pump up. Ended up setting lash with car running.

Current State Of Car: Runs with slight miss when cold. Take it for a ride and after 10-15mins gets a really bad miss (jerks the car under accelleration and rough/surging idle). Car has now started throwing codes 42(ESC) & 45(Lean) but did not do that initially (we've been troubleshooting this for a weeks)

What's Been Done Since: Re-dropped distributer and re-set timing. Changed plugs. Tried alternate distributer from buddies car. Tried different coil. Drank copious amounts of alcohol...

Any ideas out there?

 

fuel pump..pump relay..injectors..cap..rotor

 

I don't see O2 sensor on the replaced parts list.

42 should have been set when you unplugged the ESC to set the timing.

 

No...O2 sensor was not replaced, car ran fine before surgery so I didn't think we broke the O2...

The 42 piece makes sense...set when we set the timing...so the check engine light coming on and off during the drive when it's missing bad was just for the 45 (lean)...

I'll try and test the O2 sensor I guess...anything else to look at?

 

the startup cold miss shouldn't be from a bad O2 sensor.
look for vacuum leaks. also check for any air leaks between the throttle body and MAF sensor. check the injectors, they should all be clicking with the motor running.
you can use a long screw driver or an extension with 1 end pushed against the injector and the other end in you ear. just don't use that method to find a bad plug wire.
check the fuel pressure, the pump may be weak and not producing enough pressure or volume. be sure let the motor run until it starts the hot run problem and see hat the pressure is at that time too.

on the hot problem, if the fuel pressure is ok that could very well be a bad O2.
you can unplug the O2 sensor and see how it runs hot.
unplugging the O2 sensor will force the ECM into open loop.
it doesn't take much coolant to kill the O2 sensor. even using the wrong silicone can kill it.

 

Thanks for the reply. I'll try unplugging the O2 tonight. Pulled the plugs last night and they are all BLACK???

 

Also, just for giggles, pull your radiator cap and run it with the cap off, check for irregularity in circulation. What you are describing is exactly what my car did when it blew a headgasket.

I replaced, coil, distributor, ign. module, plugs, wires, computer, injectors, O2s, gaskets, hoses, etc. all before realizing it was a bad headgasket by watching the erratic coolant flow. This was confirmed after tear down, it was a good excuse for a 383 though.

 

Correct. But, a weak O2 will set the lean O2, and the ECM will keep adding fuel to try to get a non-lean reading.

You can also do a compression test to check for a blown head gasket. That could account for the cold miss.