Big Ken

my 93' 5.7L TBI has recently started missing, especially during idle. Looking at the injectors while running it seems to be getting plenty of fuel delivery, changed plugs no improvement, smoothes out somewhat once up to speed but idling is very erratic. I'm thinking somewhere in the firing, did the diagnostic but no codes stored, the Tach is all over the place and while watching the engine idle in the dark I can see a faint glow on one side of the coil between the coil body and steel mounting frame but its not jumping fire just a faint glow. I'm leaning toward ingition module or coil but just guessing. Any help would be much appreciated.

Big Ken

bringing this back to the top one time before it dies, thanks for any input

nauticstar87

Have you changed the wires?

mudmaniac

I've never seen the coil glow like that, so that would be my guess.

Big Ken

250k on the truck at least 100k on wires, so coil and wires probably as good a place to start as any, simple anyhow, I'll post results.

gotstylez

100k on wires? damnnnnnn

69luvr

My '94 is doing the exact same thing! Slowly getting worse...I was thinking fuel filter(change it every year), but it runs at WOT ok...did you ever resolve this?

69luvr

94 k1500 Sub 5.7 - slowly started running rough, tach needle jumps around all the time now - it's now getting worse...stumble at idle, a little stumble when taking off, smooths out, then stumble then smooth...never dies, just runs rough...it will go down the road at 60mph, just very roughly! Here are the things I've done so far...new distributor,cap,rotor...fuel filter, wires,plugs are about a year old...checked the tps, its within specs...pulled the TBI off, the gasket was in really bad shape(found this by shooting carb cleaner around the base), replaced it...no difference! 288,000 miles...please, any ideas? Anyone? Anyone?

69luvr

Ok guys...found the problem...let me tell you I'm old school for most things, but i am embracing newer tech as much as i can(not that OBD I is new tech...meh)...anyhow, I checked my wires with ohm meter 6-9k on everyone EXCEPT #5...wide open. Cut the wire, and found a gap of almost an inch in conductor - It would still fire intermittently! Now, this thing didnt act at all like a bad wire(think old school), the motor seemed confused, it would pull hard and then buck(stumble) then smooth out, then do it all over again...other than the tach jumping, it really seemed like a fuel issue! Replaced the wires, smooth as butta...also, replaced the TBI-to-intake gasket...it was in PIECES...I replaced the gasket before the wires, and it really didnt make any difference - shocking to me....there was about a 3/4" piece of gasket mat'l hangin out in the slipstream, about to be ingested by the motor - if you have 200+ on yours, I would recommend looking at it...mine has 288K...