Looking for some input from the experts. I have a 94 FD twin turbos with a series of mods (will list below) that runs clean from stand still to WOT in the summer but presents some sings of misfiring when the inlet air temp drops below 30C. I have a wideband hooked and logging which shows good AFRs 10.8 to 11.47 at WOT. Timing is 13L - 0T at WOT. Has anyone encountered this issue. I am fairly familiar with the rotaries and mechanically inclined so don't hesitate in getting technical. Thanks in advance!

94 FD sequential twins
New crate engine put in with 10K
Stock port
12PSI with stock injectors
Power FC w. Datalogit and commander
Innovate wideband
25row oil cooler
Greddy IC
Custom cold air
Upgraded radiator
RB cat back w. high flow cat
New stock fuel pump and filter
New plugs and wires

 

Well, as soon as I typed up the thread I started rethinking the whole issue. I slept on it and in the morning it all made sense. I realized it was time for the plugs to be replaced again. Apparently they took a beating during the summer so when the weather got cold and more fuel was introduced by the ECU to compensate the plugs were not able to keep up and misfired at WOT passed the 5K mark where injector duty hits approx. over 60%. I had been trying to firgure this out for a while and originally thought the maps and settings had to be twicked as I had done some mods over the summer including: relocated open element AIT sensor, cold air and air filters, and IC fan. So I'm glad I wrote it all down. Hope it helps anyone in the future.

 

It's always good to rethink a problem.

Kind of like looking at your bench again to find that tool you've been looking for.

Generally a misfire under load is most likely caused be a secondary ignition issue. Cooler/ denser air will cause the spark voltage requirement to go up revealing issues such as spark plugs, wires, coils.

 

Agree. Thanks for replying.