crkemppainen

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!

VenkmanP

Check the wires. I had a similar miss right after I replaced my opti. Car ran great at idle, but as soon as I gave it gas it had a miss. Had a wire that was moving over and touching metal under load.

ninetyfivevette

Definately check the coil wire. I had some random missing issues and the coil wire had worked itself loose.

bogus

yea, check wires first.

If that isn't it, it's the opti...

corvetteduke

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.

Atok

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.

runner140*

Some type of wire problem. Either coil wire/plug wire. This is where I would check first. Next I would look a each plug.

corvetteduke

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.

Z06_BluByU

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..

SupaVette

I had a similar problem on a 95 LT1 i fixed, the problem was the rib inside the opti sprak cover had corroded away, and the spark was jumping. So it was trying to fire on 2 cylinders at once.

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?

VenkmanP

Uh, no. Replacing a non-faulty opti would be a pretty dumb move.

Atok

Test your spark output before replacing your OPTI!! Get your hands on a proper HEI spark tester, I used a GM ST-125. Test each plug wire and the coil output. You may save yourself some major OPTI $$$.

Wildcat1

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.

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.

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?

VenkmanP

Replacing only the cap is false economy. You don't want to have to go back in and replace the whole thing in a couple months when the bearing goes out.

Some people have reported that the aftermarket caps are crap.

You need more than the later cap to vent it.

I didn't realize before that the opti had 150k on it. In that case yes I'd replace it. How do you know it's original?

Some people say higher voltage coil leads to opti failure.


All of the above info and more can be found easily through a web search.