Loss of power/backfiring under load

I've got a 93 Geo Metro that still gets 43mpg!
It's ran flawlessly since I put on the new timing belt several months ago.

I usually just use it to go back and forth to work, kinda babying it but the other weekend I decided to take it on a 200mi trip.

Near the end of the trip I noticed my car was not accellerating like it should.
It seems that anytime I try to accelerate too hard it wants to backfire.
It idles fine, and if I don't push it it will run up to speed, but if I get on it in the least it will backfire/misfire and I lose power.

I started with the simple. Checked the air filter, checked to see that all plugs were firing. Pulled the timing cover to make sure it didn't jump time.
Changed the cap and rotor.
Then I put a compression tester on it... 110 in all three.
No change.

I'm left with the possibility that it may be a fuel issue but I really don't know how to test that. I thought I would just change the filter but I'm not sure of where it is.

Does anyone have any suggestions?

Pastor

I would point at bad plugs/wires first. Just cause they're sparking doesn't mean they're doing a good job. Sounds very much like bad plugs/wires tho. 110 comp is good if you did the test with the TB at idle. 185psi is stock compression@WOT.

after plugs and wires check the ignition coil, if any of the insulation is melted off the coil will arc when it gets warm, and that is feels and arcs just like a misfire.

A good way to check if your wires are arcing, is to touch one when it's running(seriously). If all you feel is wire, you're good. If it shocks the sh@# out of you, it's time for new wires. And you deserved the shock for leaving them on that long :wink: