94 LT1 Misfire/Backfire
06-25-2014, 12:17 AM
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94 LT1 Misfire/Backfire Ive done a lot of research, bit haven't gotten anything concrete as a place to start... was hoping for just a little guidance...
(To start, I'm thinking this may be an optispark issue, but not quite sure...)
(Keep in mind this car sat for almost 2 years, drove it 800 miles across the country with no issues about a month ago, prob put on about 1,200 miles total, odometer reads 54,000)
So i was screwing around about a week ago and ended up blowing the upper radiator hose wide open, happened to have water with me and wasn't far from home so i limped back home (put in about 2 gallons on the way, was less then a mile from home)
On the way, when i put it under some acceleration so i could turn it off and coast, it was hesitating...
Replaced the hose, while doing so i found that the #7 spark plug had backed itself out a little (absolutely no idea how this happened)
Car ran fine but would hesitate just a touch around 5k rpms, barely noticeable
While in a store for longer then expected, i let the car idle for prob 20 min... When i came out, it was off (must have just turned off, lights were on, radio on, started right up)
Now it misfires under medium load (not flooring it but not babying it either, end even babying it to a point, under 2k rpms, struggles to go over 3,500), backfires a little (This is about 100 miles after the hose replacement, dry weather when this happened)
This car has always had starting issues, ALWAYS have to crank it twice to start it cold, 80% when warm (always assumed this was fuel pump not holding pressure when off, but once started, it runs fine, so if it just looses pressure sitting, I'm not really worried)
I haven't done anything to diagnose this yet and was really just looking for some direction before digging into this, I know how to tackle a non-LT1 motor for these issues but being that these have so many screwy features, i figured id ask for a little guidance on where/how to diagnose to start...
(Yes, it could be something as simple as wires, but the onset just seems too sudden to be that IMO, as i said, barely noticeable hesitation at WOT from 5-6k AFTER hose breaking, then come out of the store and i can't get it above 3.5k)
(To start, I'm thinking this may be an optispark issue, but not quite sure...)
(Keep in mind this car sat for almost 2 years, drove it 800 miles across the country with no issues about a month ago, prob put on about 1,200 miles total, odometer reads 54,000)
So i was screwing around about a week ago and ended up blowing the upper radiator hose wide open, happened to have water with me and wasn't far from home so i limped back home (put in about 2 gallons on the way, was less then a mile from home)
On the way, when i put it under some acceleration so i could turn it off and coast, it was hesitating...
Replaced the hose, while doing so i found that the #7 spark plug had backed itself out a little (absolutely no idea how this happened)
Car ran fine but would hesitate just a touch around 5k rpms, barely noticeable
While in a store for longer then expected, i let the car idle for prob 20 min... When i came out, it was off (must have just turned off, lights were on, radio on, started right up)
Now it misfires under medium load (not flooring it but not babying it either, end even babying it to a point, under 2k rpms, struggles to go over 3,500), backfires a little (This is about 100 miles after the hose replacement, dry weather when this happened)
This car has always had starting issues, ALWAYS have to crank it twice to start it cold, 80% when warm (always assumed this was fuel pump not holding pressure when off, but once started, it runs fine, so if it just looses pressure sitting, I'm not really worried)
I haven't done anything to diagnose this yet and was really just looking for some direction before digging into this, I know how to tackle a non-LT1 motor for these issues but being that these have so many screwy features, i figured id ask for a little guidance on where/how to diagnose to start...
(Yes, it could be something as simple as wires, but the onset just seems too sudden to be that IMO, as i said, barely noticeable hesitation at WOT from 5-6k AFTER hose breaking, then come out of the store and i can't get it above 3.5k)
