Mystery missfire

Hello, I am brand new to the forum. I have a 1994 Blazer, 93K miles, with a 350. It has a mysterios dead miss at idle. Will idle than miss, idle than miss. I have changed cap, rotor, plugs, wires, and O-2. No help. Ignition module was changed 2-months ago; new exhaust and cat. Tried to clean the TBI on the intake while running, no help. Checked timing; verified at 0 BTDC. Does ping under load, even with running 91 oct gas. Hooked up scanner; only had EST timing code and cleared that.

Any suggestions would be wonderful on what to do next. :crying:

¿Have you tried watching the ignition coil with the engine running in the dark? ¿Have you tested fuel pressure while this was happening?

No actually I haven't checked the coil; I'll get one today and change it out. Thought about it before I posted. Will let you know. I haven't taken a fuel pressure reading either, but have suspected intermittent failure. Never shot a code for it though. Will reply again when I replace the coil.

Spray carb cleaner around the base of throttle body and see if the RPM's change. I have seen several of these gaskets gone bad and created a vacuum leak.

Okay, thanks for the tip, I'll check it out and see what happens.

Replaced the coil; so far everything is good. Thanks for the assistance.

Quick update; missfire returned. Checked tightness of TBI before replacing gasket. Retightened 2.5 turns; also changed fuel filter (had black crap in filter; dark black dirt). I'll try that and see what happens...if that doesn't do it I'll drop the tank and change the fuel pump.

If the throttle body was that loose, Change the $3.00 ? gasket and pick up fuel pressure tester before you drop the tank. No need to throw $$$ at it without testing first.

Yes, I hear you....just typing away. I'll change the gasket this next weekend. I have one already. Just thought tighting it would suffice for now. I have to drive it this week for work so I'll see what transpires tonight through Thursday. I'll keep you posted.

Changed TBI gasket and put some Lucas in the gas tank. Still idles a little rough but I will drive it to see if it clears out. The throttle has loosened up dramatically and acceleration is better. I don't think a fuel pump is needed at this time. Thanks for the help.:grinyes: