4AGZE misfiring issue

[mr2gze]

Ok so my AE86 with AE101 4AGZE conversion is misfiring somewhere between 5500-6000 rpm. I completed the conversion 5 years ago, and the car has been running fault free ever since. The engine is as per factory apart from a small front mount intercooler, and made a healthy 150ish rwhp a year ago.

So here's the problem... It will rev perfectly normal up until the misfire, at which point it feels like a rev limiter, and seems to breaking down across all 4 cylinders. If I hold the throttle at say 75%, it will rev past the point and through to redline, but I can still feel a very faint misfire. The problem randomly appeared when I was driving home from work a couple of months ago.

What I've tried:
- Replaced plugs and gapped to .8
- Replaced Leads and Coils (with used items...)
- Noticed 3/7 ECU capacitors were leaking, so replaced the ECU with a AE92 4AGZE ECU

The replacing and gapping down of the plugs caused the misfire to occur higher in the rpm range (originally 4500 rpm, now 5500 rpm), otherwise the problem remains as per before.

I'm starting to think something fuel related...

Thoughts?

[Big T]

If it's fuel related, I'd change fuel filter first, check return line/charcoal canister, then reg, then fuel pump and lastly injectors. Since u say it happens across all 4 cyls, I doubt it'll be injectors. Before doing all that, check earths on head and block. Might still be a leccy issue.

[Jim621]

Common issue with GZE's - the knock sensor senses engine knock (either genuine or false knock) and pulls ignition timing.
Suggest driving carefully till you fill up with fuel again -make sure you use decent 98 octane.
Steve

[Futo_gt86]

Have a read

[mr2gze]

Thanks for the suggestions guys, this is most definitely not the infamous 5500rpm power cut issue - I know exactly what that feels like. As mentioned, the problem is a misfire, which is quite aggressive and almost feels like a rev limiter of sorts.

The 5500 rpm power cut issue causes a drop in power, but the engine continues to rev quite smoothly... completely the opposite of what mine is doing.

[mr2gze]

Thanks, I will re-check the earth's again this weekend, then move onto fuel.

Keen to hear any other suggestions.

Cheers.

[Jim621]

Measure the resistances of the leads then - post up the results and also measure the length of each lead.
the length should be proportional to the resistance.
Steve