You must be logged in to rate content!
3 minute read
Rough cold start idle, random lean condition, wet-fouled plugs
Compliments of boogieman
After the motor swap I had been experiencing some weird conditions that I was hoping were just part of the nature of having a super aggressive cam in a built motor. I even took it to a mechanic who simply cleaned off my fouled spark plugs, checked the ignition timing, and gave it back to me claiming everything was "fine" (this is exactly why I avoid going to a mechanic).
After I sent my injectors off to Witchunter Performance to be rebuilt, the idle was slightly better but I would still end up with wet-fouled plugs after about 50-100 miles (less when in town). I also still saw intermittent lean conditions on my wideband along with the same, albeit less noticeable, rough idle.
I tested the ignition switch by jumpering the starter to the battery, no improvement.
I tested the WOT and idle switches: fine.
I tested the ECU CTS: within ohm specs.
I tested the ISV: holds air and hums when powered.
My CO Pot is adjusted correctly
Static timing should be right (after dozens of times checking it during this process).
After some research, I settled on a plugged cat or a weak coil being the most likely candidates/ the easiest to solve. I got a Bosch replacement coil and threw it in.
The coil was kinda tricky to remove and required removing the boost pipe from the throttle body and also disconnecting the ISV hose from the same pipe to allow clearance to get the coil out. I ended up dropping and losing the lower nut for the coil bracket, so I put a rivnut on the bottom hole so I can screw and unscrew the bottom of the bracket blindly. I left the top one alone since I have to put a ground strap connector under that bolt.
So far the warm up process is much more gentle, rising gradually from 12.1:1 to 14.7:1 as the idle settles. I caught a few blips of 15.0:1 but I will only start hunting AFRs down again if it jumps to 16:1 -18:1 on a cold start and the plugs are again fouled.
Pictured below is the new Bosch coil with some... decoration.
This did not completely solve the problem. I ended up screwing in the idle screw tighter and adjusting the ignition timing a bit and while the idle is pretty high (1050 RPM) the AFR is very stable, floats down rather than up when it blips, and the car starts beautifully when warm or cold.
