You could do a quick resistance test with a multimeter. You'll find resistance parameters in Haynes (or probably a bunch of places online). You don't even have to remove the coils.
I checked the coil on my Pathfinder and it checked out good, but it wasn't. It passed the ohms resistance test from + to - and from the terminal post as well. Couldn't even tell visually that it was bad, but when hooked up and turning as to run, it would arc out. Shorted out between the coil and distributor. Loosing the current, i.e. low / weak spark.
VT247
Here's what I'd look for. Check to make sure the catalytic converter isn't clogged. That could cause the engine to bog down due to excessive back pressure. Check the fuel pressure. Low fuel pressure could cause the engine to starve out at higher rpm's. This is because the fuel pump can't keep up with the engine demand. Just a couple things to consider. LMK
VT247
You'd probably get a code from a bad cat, but not always. Running out of ideas here. Runs good at 1/4 throttle, sometimes has full power but quickly drops off. Runs good at idle. Any more description of the symptoms? I'm trying here : /
VT247
An easy test for converter plugging is done with a vacuum gauge. Connect the gauge to a source of intake vacuum on the intake manifold. Note the reading at idle, then raise and hold engine speed at 3,000. The needle will drop when you first open the throttle, but should then rise and stabilize. If the vacuum reading starts to drop, pressure may be backing up in the exhaust system.
Also while you have the vacuum gauge connected, with the engine fully warmed up, the reading at idle should be 18 - 20 InHg. At 3,000 RPM, it should be around 21 InHg. If readings are under 18 InHg, check the intake manifold nuts to make sure they are tight. Also check the intake plenum bellows at the throttle valve and at the MAF for cracks or loose clamps.
Yeah runs good at 1/4 throttle and sometimes if pump the throttle it will go then lose power again until I go back to 1/4. No engine light. Idles perfect. Changed the fuel filter, coil, cap, rotor, and wires. I cleaned the MAF. It doesn't make sense I have no idea what's wrong. The gas mileage isn't very good either less than 14 mpg.
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