1993C4LT1

I went WOT yesterday, and felt a Missfire at 3,000 rpm. Earlier this morning, I was curious to see if I would get any knock on my scan tool. Sure enough I did. I was driving and wasn't able to read it good, but I did see it go away from zero. I believe it was at about 4, the knock retard. The miss seems to be more noticeable today. Yesterday, I only felt it once at WOT. Today, I felt at part throttle. Though not all time. Hope I am making sense. Just checked for codes, none. Put 93 octane in it last Tuesday.

antfarmer2

How old are your o2s? How many miles on it?

1993C4LT1

A year old. They are working fine based on my scan tool.

antfarmer2

I would take a look at them for melted wires. What brand did you use? Also look for anything loose like motor mounts or exhaust banging that could set off the knocks. And the wires to the knocks might be shorting out.

1993C4LT1

Fuel pressure at key on, 42 psi. Running, 36-38 psi. Safe to say the fuel pump isn't the reason for the miss, right?

antfarmer2

Fuel looks good.

1993C4LT1

Just let the car warm up, checked for arcing on the plug wires, none. Question, would something with the knock sensors cause the hesitation/misfire? As I said, it doesn't always misfire. I was looking to do the test that 93rubie shows on how to test the opti with a multi meter. But I don't know how to make t pins. No loose exhaust or anything.

antfarmer2

Yes might just be a rubbed wire on the knock check them when you look at the o2 wires.

1993C4LT1

Before going out for a ride today, I tested fuel pressure just because. At first key on, engine off, it only went to 24 psi. Went to key on again, then it was at 42 psi. Could the fuel pump be going bad? It ran great, no misfire. Knock on wood that it stays that way

PatternDayTrader

Not unusual. I wouldn't worry about it.