Hellbent
NAXJA Forum User
- Location
- san diego, california
This is kind of a new one for me, I've got some ideas and will be following up as I go in order to possibly help future searchers.
Background: new to me '88 renix/auto/242 that I've been working on, which has been running great for the last 700 or so miles that I've been driving it, starting misfiring pretty badly last night on a long, steep highway grade.
after messing around with it, I have determined that it only happens under a sustained load of more than a minute or two. Cruising flat streets, I can't get it to happen no matter how many times I punch it. As soon as you hit a grade and sustain a load on it for a couple minutes, it'll start to miss heavily and randomly. The more you push it, the worse it gets and the slower you go.
What I think is a clue, is that when this happens, the tach jumps wildly from 3k down to 500-700 and back and forth 1-2k rpm in a split second. You can hear it pop lightly out the exhaust while it's happening. If you ease off the throttle it gets much better, but continues even on the downhill side for several more minutes. After that, it's fine until a sustained load again.
Fuel pressure stays good the whole time. All grounds were refreshed after I bought it, all sensors test good. Cap, rotor, wires all *look* good.
I feel like it's most likely a bad ign coil, bad icm, or possibly cps.
Going to swap to a known good coil and icm this evening and see what happens.
Anyone ever go through something similar?
Background: new to me '88 renix/auto/242 that I've been working on, which has been running great for the last 700 or so miles that I've been driving it, starting misfiring pretty badly last night on a long, steep highway grade.
after messing around with it, I have determined that it only happens under a sustained load of more than a minute or two. Cruising flat streets, I can't get it to happen no matter how many times I punch it. As soon as you hit a grade and sustain a load on it for a couple minutes, it'll start to miss heavily and randomly. The more you push it, the worse it gets and the slower you go.
What I think is a clue, is that when this happens, the tach jumps wildly from 3k down to 500-700 and back and forth 1-2k rpm in a split second. You can hear it pop lightly out the exhaust while it's happening. If you ease off the throttle it gets much better, but continues even on the downhill side for several more minutes. After that, it's fine until a sustained load again.
Fuel pressure stays good the whole time. All grounds were refreshed after I bought it, all sensors test good. Cap, rotor, wires all *look* good.
I feel like it's most likely a bad ign coil, bad icm, or possibly cps.
Going to swap to a known good coil and icm this evening and see what happens.
Anyone ever go through something similar?