First post, so be gentle.
I have a mostly stock 1988 IROC-Z 5.0 liter(305 TPI) 5-speed t-top car.
Non-stock parts include:
Adjustable Fuel Pressure Regulator (set at 40 psi, no vacuum hose to AFPR)
Autometer A/F guage, O2 sensor switched before the computer
switched speed sensor (VSS)
mildly ported plenum
modified air boxes with K&N filters
MAF with no screens
no catalytic converter, no A.I.R pump, no EGR, Dynomax muffler
timing set at 2 degrees BTDC
new MSD distributor

I have had this car for six years and it has been running in this configuration (except for the distributor) for 5 years
with no problems. The A/F ratio is tuned with the O2 sensor switched "off"(the computer can't read it) to about 12.5-13:1.
This ratio shows as the first two green lights in the "rich" portion of the A/F guage. With the O2 sensor switched "on" the
computer reads the O2 sensor and adjusts normally.
Two weeks ago the check engine light came on(code 44- O2 sensor lean) and the car immediately started sputtering
intermittantly. I assume this is due to a switch to a predetermined fuel and timing map(Limp Home Mode). Two days later the
car refused to crank. The refusal to crank was due to a bad reluctor ring in the distributor which prompted the install of
the new distributor. I assumed that the code 44 was in some way related to the bad distributor but it was not. I promptly
did the most obvious thing to try to fix the problem, replaced the O2 sensor. I still get the same code 44.
The specific conditions for setting the code occur when maintaining a steady speed of about 70 mph for 10 seconds or more
on the interstate. The really confusing part is that I can crank the car with the O2 sensor switched "off", drive down the
interstate and still set a code 44(after clearing the codes, of course) even though there is no O2 sensor attached to the
ECU !!
Any suggestions would be greatly appreciated.

 

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