Three days ago, I replaced the cap and rotor (the old cap had the carbon tip broken off). I was thinking of ordering a resistorless rotor, but the PO had a bosch in there for 10+ years, so I figured it wouldn't hurt to go with the factory part. I just checked the rotor and it still looks good. Went for a good 30 mile test drive after changing the cap and rotor and all seemed much improved, but still felt like it was not running great. I did not have a working tach at the time, so I could not tease out the misfire as easily. I wired up the tach correctly on Saturday, installed the front spoiler, and then had the test drive where I started questioning wiring.
The reason I am thinking wiring and possibly signal noise is the problem is very intermittent. Sometimes the car runs well, and yesterday we went for a test drive and it ran like complete crap. Lots of misfiring above 3k, tried pushing it some more to see what would happen and got a backfire at 5k. Took it back to the driveway to check timing and it ran okay sometimes (got it up to 5k rpm no problem) and misfired at other times. Timing at idle was hitting the 5DBTC mark pretty well, made a custom mark at around 25 using a paint pen and when I was able to get the car smoothly up in the rpms it seemed to hold well before that mark.
I just looked and the green wire looks good all the way from the CDI connector to the black connector at the distributor. See picture of wire and the top of the rotor below.
I plan to drain the tank and also check the screen filter, but the fuel filter and pump are new. I am running a mix of 87 and 90 E0 gas, so I am tempted to try higher octane fuel, but I can only get E10 where I am currently.
Thanks so much!
