my 87 5.7 TPI is misfiring at idle and pinging now, after a 1300 mile drive. it's idling 200- 250 rpm too high now at 750-800 rpm in drive and pings worse when it's fired up cold. there's a popping sound in the exhaust at idle from the misfiring.
the problem is intermittent , every now and then it clears up and the idle drops down to where it should be, although most of the time it's there. so i'm guessing it's electrical.

the distributor had some oil inside it coating the base, ie around and on the ignition module. there's no oil outside the distributor... i assume this blew a seal inside the shaft and is leaking up.
could this be causing the problem?? if so is this leak fixable, or is there shaft play, ie i need a new distributor ?? the car is low mileage, only 80000 and never had a problem before.

so far i've replaced a bunch of parts w/ no success -
igntion module
O2 sensor
plugs
IAC ( destroyed it by spraying carb cleaner in the idle passageway.)

have also checked the coil, TPS, cap, rotor, fuel pressure, EGR, thoroughly checked the plug wires and gone over every single vaccum line.
the base timing is correct, it's at 6 deg BTDC right where i set it 2 years ago.

 

Could it? Probably. Best bet is to get it tested. As for the IAC and TPS did you set them properly or just inspect them? How do the plugs look? Have you hooked up a vacuum guage yet?

 

the TPS was set to .54 volts, as it measured something like .42 when i checked it. although it didn't seem to help.
i didn't do the IAC throttle blade adjustment when the new one went in... maybe i'll have a look.
first i'm thinking of pulling the distributor to have a better look at the pickup coil and maybe find the blown seal.
may try replacing the CTS also.

 

the plugs had regular deposits didn't look to be running rich, although the problem hasn't been going on very long. the plugs did have white deposits from the pinging i'm guessing.
re the vaccum leaks - i pulled off every line one at a time and plugged them. didn't find anything. also sprayed carb cleaner around the intake and throttle body and checked the EGR and fuel regulator diaphragms.

 

for anyone reading this thread just thought i'd let you know the problem was eventually solved... it was the ECM. the PROM and MEMCAL were fine... it was something wrong in the ECM itself.

 

A quick and easy fix for oil seapage up the distributor is to remove distributor, then remove roll pin, gear and shaft. Then simply drill an 1/8" hole slightly below the mounting flange, where it mounts to the intake manifold. Then reassemble. I generally do this whenever I have to pull one with some miles on it, so I don't have to remove it again later.