Hesitation at 3k to 4K rpm at WOT

[Ron240sx]

It seems as if my 86 300zx (vg30e) has quite some hesitation when it's getting warmed up. I've replaced the fuel pump. The symptoms are still the same. It seems like it leans out almost like it's at rev limiter. It's only once it's warming up and getting to normal operating temp. When it's cold first thing in the morning it accelerates great. But once it starts to warm up it studders around 3k to 4.5kish rpm any gear. But only half to WOT. 5k to 6.5k rpm it seems to get the power back.

The car has codes 23, 31
Has new chts and sub harness
New plugs ngk bcprs6es or something close to that, there the factory plugs gapped at .40, cap, rotor, and coil are new.
Timing has been set to 20* with a timing light.

When I pulled the old plugs. Which weren't that old, they didn't show signs of rich conditions and they were burned a light tan color.

The FPR has been tested with a gauge running at 28psi at idle with vacuum applied. With no vacuum applied it's at 37psi at idle. Everything FPR wise is current to factory specs.

That leaves me to question if the ecu could be at fault. Or if I seem to be overlooking something.

Any positive help would be appreciated greatly.

[evildky]

Generally speaking rpm related issues are the result of the mas. Warm restart/rich warm condition generally is a result fo the chts (which you've already addressed) or the O2 sensor. The fact that you have a codes one for the ecu, I'd start by replacing the ecu.

[Ron240sx]

Alright I have solved this issue. I replaced the ecu. Long story short it fixed the problem. my old ecu was was number 25, which I believe was an automatic ecu version. Though my car is manual I switched to number 24, and it was successful. Hopefully this more or less will help someone else stumped on the same issue later. Until then cheers z31 forum.


Big R