Accent LC (2000-05) :: Engine Bogs Down Past Partial Throttle

Back in July some time I went out to my Accent (00' 1.5L) to go to work and it didn't want to turn over. Normally it's quick to start. So I turned off the A/C and it started right up. I went about my way. The next day, same thing happened. I thought it might be a camshaft position sensor, figured I'd be ok and headed to work. Got about 2 miles from the house and it died. So I pull over and try to start, no dice. Can't get it to start to save my life. We have it towed to the house and park it. This happened about 3 days before we closed on a new house, and having other cars we decided this needed to stay on the back burner. About a month later, I do some troubleshooting (not enough) and decide that the fuel pump is bad. I don't hear it coming on when I try to start the car. So, I replaced it. Turn the key, still no noise from the fuel pump. So, I leave it sitting for a couple of more months. During this time I've done more research than I care to admit regarding this car. I find out there's a Fuel Pump Check under the hood. I checked all relays/fuses before replacing the fuel pump. But didn't thing to test the fuel pump check. My loss there.

So, Saturday was a nice day I spent about 5 hours with my father and brother-in-law working on the car. First thing we do is Put 12v to it and the fuel pump comes right to life. So, we know it's not the fuel pump. Check the connections with a multimeter, we have voltage where we should and grounds where we should. So relay is working, wires are good. Finally we find a schematic of the fuel system and go hunting for the MFI (Engine) Control Relay. Well, I don't know how it happened since it's inside the car, but when we pulled it, it was rusty as all get out. We replaced it and the car still didn't want to start. Checked for fuel pressure at the rail, yup, we got fuel. So we sprayed some starter fluid into the intake and it finally fired up and ran. But it's not running how it ran when it died on me back in July. This car has been extremely reliable until this point. It's not a race car, but it will do 55-60 comfortably and get 38mpg doing it. Well, after it starts it's idling very rough, surging from 500-1500 rpm. We let it run for about 30 minutes and it continues to surge the entire time but doesn't stall. So I take it out for a test drive, as long as I only give it partial throttle 10-15% it gets up to speed in an acceptable amount of time. But anything more than that and it bogs down and will not accelerate. So I drive it home and park it.

The next day, I change the spark plugs, fill it up with some fresh gas, top off all the fluids and throw some Lucas fuel treatment into the tank. It started much better, but still surges, just not as badly as before. And the acceleration problem remains. I'm going to replace the wires next and see how things go and I've also ordered a new MAF and some other goodies. Oh, car has 133,000 miles on it. I do not know if the timing belt was ever changed and nobody in my family remembers if it was done either. I'm leaning towards being on borrowed time and the timing kit is one of the goodies mentioned. So, I've got a busy weekend coming up. But, I have to get this car back on the road so that my wife who is now commuting 140miles round trip per day can save some money on gas.