Replaced the opti and wiring harness for it about a month ago because the car was struggling to start and then just stopped starting. I thought it was something in the fuel system so I started off by changing the filter then the pump and checking the injectors. Nothing worked. So we moved onto the ingnition system and it ended up being a deteriorated wiring harness for the opti and a vent tube that was being pinched that caused the opti to fail. Now a month later I have a horrible misfire and it got so bad that I barely could make it hope because it was misfiring so bad.

Most of the time it sounds like just one cylinder is not misfiring and it was mostly in low rmps, once I would hit 3000rpm it would run on all 8.

Then it got to the point if I opened the throttle any more than 35-45% it would misfiring under any kind of load but at idle it would run fine.

Then it got to the point where it wouldn't even idle fine.
So I changed all the wires since it's one of the easier things to do and still have the same problem.
Checked all the plugs they seem fine and tested all of them and they seem fine. Still have the same problem.

I didn't bother to change the cap and rotor when I swapped out the opti just because of money at the time. Anyone have any kind of insight as to what this could be? I'm thinking about just going to the LTCC system since I have the money after x-mas and b-day.
Can someone please help tho so I can figure out what it is before I drop a ton of money?

 

I thought swapping out the opti was replacing the cap and rotor. I could be wrong but to me those are the parts to do when you do a tune up. For 100 to 150 you can get the pair from several aftermarket companies. The coil wire or the opti wire could also be a problem. Plugs not tight, plug wires not on all the way, or damaged plug wires should be an easy check.

 

i would check plugs and plug wires
i had a low RPM miss, and it was the plugs, but im doing wires and cap and rotor too just because

 

this ignition system is driving me crazy

 

Well, yours sounds exactly what happened to my car. Mine would backfire like crazy too... but it got slowly worst untill it would hardly even idle. Changed so many things and when i finally broke down and took the opti off, one of the screws came lose off of the rotor so there was only one holding it on. So you could turn the rotor freely, got a new screw and fixed the problem.

 

When changing opti change the COMPLETE thing.

Install a new rotor and cap.

 

When you "replaced the Opti", what did you replace? Just the base housing with the optical sensor? Have you inspected the wire towers in the cap for corrosion? Check the coil wire for corrosion? Chech the IC Module and the coil?

How did you "test all of them (plugs)"?

 

What did you do exactly to rule out your fuel system?

 

tested shrader valve, just put new fuel pump in, ect... checked all that and is running fine.

Just got done replacing coil, wires, and plugs, it is running a little better but still missing. 1st gear it runs normal, 2nd, 3rd, 4th, ect it is missing throughout the rpm range after maybe 1/2 throttle. And yes I just replaced the optical part of the opti-spark system I didn't have the money at the time to replace everything and that was the quickest way to get my car back on the road. I am realizing that was a bad idea now but don't bash me for doing so, not all of us have the $ to fix everything when needed, especially a college student

 

Not bashing just trying to fix the thing with the correct advice on HOW TOO.
Ya still need to replace the cap and rotor.

 

Not bashing anyone..... just trying to be clear on what you did when you "swapped out the Opti". Its always easier to help someone if you know all the details.

 

i know i know, just frustrated because it's hard to tell exactly what is wrong and I appreciate ya'll trying to help me. My dad dug into the car a bit today since I had to work from 9-8 i don't know what he got done or figured out tho since he isn't home now. One of my buddies stopped by who is pretty knowledgeable with LT1s and is a tech for Mercedes. He said to check the vacuum lines and vacuum pressure ect... also said to check the 02 Sensors and the wiring harness since i have longtubes.

But the car is running better than it did before but it is still misfiring. I can at least drive it down the road without it sputtering to the point where it barely moves. Its jsut a constant misfire through every gear except 1st

 

this might have been the problem......?

bad cap



due to loose rotor