LT-1 Random misfire problem
Thread Starter
Racer
Joined: Apr 2004
Posts: 298
Likes: 1
From: Springfield Missouri
LT-1 Random misfire problem
I need some input on this problem. After not running the car for almost a month, the engine now has a random miss at all RPM. It is more noticeable during light acceleration between 1200-2100 and almost completely goes away when the engine is unloaded...like when you have the cruise control set and start going a little downhill...
it gets really bad when you stomp it and start pulling past 4500 in first. the engine misses so bad I thought I had hit the rev limiter the first time it happened.
If this was a points style ignition, i'd say it was "smearing" the spark, or the vaccum advance was jacked up.
Is this a sign of a failing Opti, or is it somthing as simple as dirty injectors?
This is a '93 and is my first "new" car...as in, made after 1971. Pardon my ignorance on the hight tech stuff!
THANKS in advance!
it gets really bad when you stomp it and start pulling past 4500 in first. the engine misses so bad I thought I had hit the rev limiter the first time it happened.
If this was a points style ignition, i'd say it was "smearing" the spark, or the vaccum advance was jacked up.
Is this a sign of a failing Opti, or is it somthing as simple as dirty injectors?
This is a '93 and is my first "new" car...as in, made after 1971. Pardon my ignorance on the hight tech stuff!
THANKS in advance!
8th Gear
Joined: Sep 2003
Posts: 8
Likes: 0
From: Allentown PA
I am chasing the same thing on my 96 LT4. I replaced the wires (that was tough on the drivers side, removed the alternator and moved the compressor over too to get to the wires as well as removed the tensioner and idle pulleys). My situation is similar except my is rough on idle now and is missing seriously. I will probably purchase a new Opti Spark (>$450) and put it in. Too bad I already replaced my water pump last year, should have done the opti then.
If some one knows that clogged injectors or bad O2 sensors can throw a P0300 Random Miss fire let me know before I buy an expensive Opti.
Good luck its tight under that hood.
If some one knows that clogged injectors or bad O2 sensors can throw a P0300 Random Miss fire let me know before I buy an expensive Opti.
Good luck its tight under that hood.
Melting Slicks
Joined: Apr 2003
Posts: 2,150
Likes: 6
From: NS
I had the exact same problem with my '95. The solution....replace your spark plugs.
I borrowed a HEI spark tester from my local GM dealer and tested the ignition output following the procedure in the service manual. I had lots of voltage at the plugs. I replaced the badly worn AC plugs and bingo, never misfired since.
I borrowed a HEI spark tester from my local GM dealer and tested the ignition output following the procedure in the service manual. I had lots of voltage at the plugs. I replaced the badly worn AC plugs and bingo, never misfired since.
8th Gear
Joined: Sep 2003
Posts: 8
Likes: 0
From: Allentown PA
To update you if you do buy an opti, I just bought mine from Sam Taylor Buick and Cadillac ( http://www.samtaylor.com/html/parts.html ) for half price including over night delivery from FL to PA. All local dealers in PA wanted twice the price.
As for my issue I also replaced the spark plug when I did the wires as noted previously with little to no change. If it is not the opti I will be back on line one minute later. Wish me luck, I could use it.
As for my issue I also replaced the spark plug when I did the wires as noted previously with little to no change. If it is not the opti I will be back on line one minute later. Wish me luck, I could use it.
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Race Director
Joined: Nov 2000
Posts: 17,103
Likes: 39
From: stop the fun suckers
I had a similar problem after installing a new opti.. it turned out the screws holding the opti on loosened up and allowed the opti to wobble in place a bit.. before I went down that avenue I would verify spark from the coil, mist water on the wires and check for arcing, pull the plugs and check the gap and make sure the resistance on all the wires is less than 30,000 ohms..
Thread Starter
Racer
Joined: Apr 2004
Posts: 298
Likes: 1
From: Springfield Missouri
I replaced the plugs less than 1000 miles ago. NGK tr-6 plugs.
This is a confusing matter, since the car was running just fine prior to going into the shop and I didn't go near the ignition system.
so i am going to go ahead and replace the opti and plug wires...... might as well, right?
the question is now... What kind of performance upgrade can be done instead of swapping in a stock opti?
I saw a cool coil-on-plug system with LS-1 components that could be done, but where can I get one?
This is a confusing matter, since the car was running just fine prior to going into the shop and I didn't go near the ignition system.
so i am going to go ahead and replace the opti and plug wires...... might as well, right?
the question is now... What kind of performance upgrade can be done instead of swapping in a stock opti?
I saw a cool coil-on-plug system with LS-1 components that could be done, but where can I get one?
Melting Slicks
Joined: Apr 2003
Posts: 2,150
Likes: 6
From: NS
Originally Posted by crkemppainen
I replaced the plugs less than 1000 miles ago. NGK tr-6 plugs.
This is a confusing matter, since the car was running just fine prior to going into the shop and I didn't go near the ignition system.
so i am going to go ahead and replace the opti and plug wires...... might as well, right?
the question is now... What kind of performance upgrade can be done instead of swapping in a stock opti?
I saw a cool coil-on-plug system with LS-1 components that could be done, but where can I get one?
This is a confusing matter, since the car was running just fine prior to going into the shop and I didn't go near the ignition system.
so i am going to go ahead and replace the opti and plug wires...... might as well, right?
the question is now... What kind of performance upgrade can be done instead of swapping in a stock opti?
I saw a cool coil-on-plug system with LS-1 components that could be done, but where can I get one?
Racer
Joined: Apr 2004
Posts: 487
Likes: 0
From: Huntsville AL
I've had this problem many many times. Once was the 02 sensor(s), a couple other times it was the wires. I have had to replace them each year. Another time was the opti, but only after some idiot drained my water pump onto it when I was having him install a meziere elect water pump. And the last time was when I became the idiot and switched plug wires by accident. It never got out the driveway that time.
I believe the failed 02 caused the engine light to come one.
In this case, I also say to replace the wires and optispark wire....but not the opti if you don't have to. I went with a Dynaspark when I had to replace my opti though. I also suggest doing whatever it takes to make sure the new wires are as far away from metal as possible. I already burned one of my new Taylors, I now have them tie-wrapped away from the headers and such.
I believe the failed 02 caused the engine light to come one.
In this case, I also say to replace the wires and optispark wire....but not the opti if you don't have to. I went with a Dynaspark when I had to replace my opti though. I also suggest doing whatever it takes to make sure the new wires are as far away from metal as possible. I already burned one of my new Taylors, I now have them tie-wrapped away from the headers and such.
Thread Starter
Racer
Joined: Apr 2004
Posts: 298
Likes: 1
From: Springfield Missouri
I got it locked on now- I bought a new cap and rotor, the 95-96 kind, so i can hook it up to a vent line.
I also bought a new set of plug wires. Taylor Thundervolt50 direct-fit. So far as I have found, they look to be the best direct fit wires for the LT1....a little pricey, but hey, every little bit helps.
I say the stock opti and wires have served their usefulness at almost 150,000 miles. Time to do some minor upgrading.
On a side note, Is it worthwhile to replace the ignition coil with a higher voltage unit? is one even available?
AND who has used a Mallory Hyfire digital-6 ignition box on the LT-1? Does it connect to the factory wiring harness, or was it a custom hack-up?
I also bought a new set of plug wires. Taylor Thundervolt50 direct-fit. So far as I have found, they look to be the best direct fit wires for the LT1....a little pricey, but hey, every little bit helps.
I say the stock opti and wires have served their usefulness at almost 150,000 miles. Time to do some minor upgrading.
On a side note, Is it worthwhile to replace the ignition coil with a higher voltage unit? is one even available?
AND who has used a Mallory Hyfire digital-6 ignition box on the LT-1? Does it connect to the factory wiring harness, or was it a custom hack-up?
Safety Car
Joined: Apr 2003
Posts: 3,793
Likes: 9
From: VA
Originally Posted by crkemppainen
I got it locked on now- I bought a new cap and rotor, the 95-96 kind, so i can hook it up to a vent line.
Some people have reported that the aftermarket caps are crap.
You need more than the later cap to vent it.
I say the stock opti and wires have served their usefulness at almost 150,000 miles. Time to do some minor upgrading.
On a side note, Is it worthwhile to replace the ignition coil with a higher voltage unit? is one even available?
All of the above info and more can be found easily through a web search.
