my 97 ford taurus 24v DOHC has the CEL on. I went to AutoZone and pulled the code P0430 Catalyst System Efficiency Below Threshold Bank 2 Rear. Could a bad O2 sensor cause the engine to run poorly when accellerating and idling. If I accellerate slowly, it wont be noticeable, but if I accellerate normally, it is much more evident. It's almost as if not enough air or fuel or both (intermittently) is being delivered to the engine for optimal performance. Could this be causing my car to stutter when accellerating to highway speed or while idling. Once I am up to speed, everything smooths out. :dunno: :eek: :confused:

OK, pulled new code P0305 misfire cylinder 5 and the P0340 code for catalyst below performance threshold bank 2 rear cleared itself automatically. What the heck? Since a misfire dumps fuel into the cat unburned, will that set the cat code to go haywire

OK, got in my car today drove a bit on the highway with the CEL steady. Went to Ford to check a few prices on parts. Turned the car back on drove a few miles up the highway with no hesitations or indications of problems and the light went out. This light has been on forever. To double check it was not a burned out bulb, the next time I got in my car I put it in the "on" position and the light is not defective. So I had a cat code, misfire code, egr code and now they are all gone. Still a very faint hesitation issue when accellerating hard. Do you think ignition wires culprit? Or EGR backpressure sensor issue? Or maybe even a PCM issue itself?

I have the same engine in my 98 taurus and i also got a cylinder 5 misfire code. My only problem was that the spark plug wire boot had been tracking spark out of it. I would start with replacing the spark plugs and wires. It is a tricky process and if you would like any help with instructions let me know. When you are changing the plugs you will take off the intake manifold, when you have that off, on the right side there will be a control for the butterfly valves that you will see in the dual manifold runners to the heads, see if the cable isnt broken. Mine was and it was an easy fix ($185 for the part) but now my car runs great. You may also want to replace the plenum gasket while you're in there.

Its your cad convertor I'd say. My brothers did the exact same thing, exactly as you described it, it was "bogging down" and not gaining speed, making an odd sound when you accelerated hard, and did "okay" when you gained speed as normal. We got a new cad convertor in it by the dealership, went back and it drove perfect, and the moaning sound that was there was totally gone with only a roar that we expected and knew the car should have was there :) .

I'm gonna run it another week, it has 172,150 original engine/tranny miles, yes all mine. Gonna take it to my cousins for his test drive, advice w/steering parts installed. Thanks for the help on the wires, I'm on my third pair. The first pair lasted 92k. The second pair (Borg/Warner) lasted about 60K before they started arcing. The 3rd pair just suck. The crimping to the wires inside the boot to the spark plug came off on cylinder 1. Repaired it, now cylinder 5 gave me problems. Mashed down really really good on the plug at both the boot and the ignition coil pack. Around town driving ok highway driving great, just afraid of quick starts at lights as still showing issues. Highway passing is terrific. Its the starting line accelleration now that I'm having the issues with. NO OTHER DRIVEABILITY CONCERNS. By the way, I just reuse the plenum gasket as it is a reusable plastic one, not aluminum that oxidizes and pits.

No odd sounds. you probably heard something like marbles in a muffled tin can. Not this. And it just dissappeared. GONE. Capoot. All codes. What I think was/is happening, is the misfire is dumping unused fuel into the cat (when it occurs) and that is filling up the cat blocking the air flow. When on a highway trip (about 15 miles) that fuel is burning off, and is allowing for the air flow to regenerate and perform within specs, but not enough time/trips to reset the computer DTC. I think that is why when doing short quick trips around town, the fuel never had a chance to burn off during the trips, still causing the cat to be blocked but not defective. The more I think about this the more I am convinced that the cat code/O2 sensor was the symptom and not the problem. You were both right to some extent now that I had a chance to think this through.

Was wire #5. the connector that seats on top of the plug was forced way up inside the boot and was not always making a connection. swapped with new wires. everything dissapeared and runs great again. :cool: