Update: Loss of power at 3k RPM = 0 volts on O2 sensors?

[Rockscout]

Long time user of this forum. I think this is my first post. Bear with me.

Edit: Please skip to my most recent post. I've ruled out a lot working on the 2002 SOHC all summer. It runs fine until you go above 3000 RPM. Then it acts as if a governor is kicking in.

 

[Rockscout]

Just put in a new fuel filter and that's not the trouble.

 

[rusty ol ranger]

Yes, in theory anyways, if the oil pressure drops it coulf starve the lifters...valves wont open...no power.

However i dont think thats the issue.

When this happens do you notice power being cut to other stuff? (lights, blower, etc?)

Check engine on?

Im thinking the engine is stalling which is why the gauge shows the pressure go down...OR....you have an electrical (ground?) Issue thats causing the engine to stall and also killing the gauge.

That engine would let you know if it was actually low on pressure. Generally. Athough i did have my 97 460 do this (without stalling) and it turned out my mains were shot.

You could also hook up a real pressure gauge and watch what the pressure does. The factory gauge is basically an idiot light with a needle.

 

[Rockscout]

Thanks for the reply. Yes, I think my next step will be getting an oil pressure gauge on there.
Then the power dips there's no change in the fans or lights. There's no signs of any electrical issues. There's no codes, no check engine.
I haven't seen the oil pressure gauge go out since the other day. But it happened simultaneously with a bad loss of power, so that has me worried.
I'll add that I sometimes hear the lifters knocking in this engine. I'll change the oil and the knocking goes away. It's currently not knocking.

 

[Rockscout]

Finally got an oil pressure gauge on this truck 15 psi @ idle. 40 psi @ 2000rpm .
42 psi @ 3000rpm

The loss of power is only at 3000rpm where the rpms blip rhythmically.

Seems like oil pressure isn't the issue. I could see a bad ground causing this, but I don't know how to check that.

As a recap I've ruled out TPS, fuel filter, air filter, and battery. No codes. The truck works as it should until you hit 3000 rpm.

I'm just looking for a correct diagnosis before I start randomly replacing fuel and ignition components.

 

[Rockscout]

I'm continuing to have loss of power above 3000 rpm. I've replaced fuel filter, spark plugs, plug wires, and coil pack. The alternator is good. No codes.
The strange thing is when I hit 3000 rpm all the oxygen sensors go to 0 volts!

Any Ideas? @rusty ol ranger suggested a ground issue, so I've been on the lookout for that.

 

[Rockscout]

So on a hunch I learned this engine has a 3k RPM rev limiter in park and neutral. But mine is kicking in in drive!

 

[SenorNoob]

IDK about 02 but earlier trucks had a single input to the PCM for that purpose. MIght look into it.