99 crown vic hesitation

[danielsaxxon]

My car has 114k miles on it and has a hesitation. There was a faint hesitation a while back. I figured it was the 2 sensors so I replaced them. That was when I realized that there are four of them. The faint hesitation had not come back and since I could not get to the other two I put replacing them off for a bit. I changed the plugs at about 100K. I was thinking that the hesitaion was coming from the O2 sensors that I didn't replace. I was told that if the O2 sensor was causing the hesitation that the check engine light would come on. It has never came on. Is it possible that the sensors could be bad with out throwing a code? I was thinking that since there are four of them that it might be possible but I don't know how the on board comp. interperates the signals from them. I will probably be paying someone to replace these two sensors but was wondering if the hesitaion could be from something else that I wouldn't have to pay someone to fix since I do most of my own maintenance and would hate to pay for something that I could do myself.
Any information would be greatly appreciated.

[mechhound]

I would try a bottle of name brand fuel injector cleaner or Sea Foam in your gas tank. Add the cleaner after you pull up to the gas pump, but before you fill the gas tank.(full or nearly full). Also if you regularly use the 10% ethanol and you have a choice in your state, try just the pure gasoline. The cheapest, lowest octane should be fine. Hope this helps.

[danielsaxxon]

Thanks for the quick reply, I forgot to mention that I did add a bottle of injection cleaner. I haven't used the whole tank of gas yet though. I guess I could go for a short trip to run it through.

[rhandwor]

When do you get the hesitation coming to a stop or taking off. How bad is it does the motor shake. A leaking egr valve will cause some hesitation. You could clean the idle control valve for starters also clean the egr valve and the inlet to the valve. A bad plug wire will also cause problems use an ohm meter to check them.

[danielsaxxon]

The Idle air control valve is new. The old one didn't like the colder weather here in pennsylvania. A few days ago I finished the tank of gas with the fuel injector cleaner. The car seems to be running ok now. The hesitaion was during acceleration when the car was under a load like going up a hill. It felt like a fish on the end of a fishing pole. When it started acting up it would do it when the car was under a load and also when slowing down to a stop. It never stalled. I thought about the egr valve but haven't done anything to it yet. Was also thinking about the fuel filter as well. It never seemed to hesitate or run rough when idling in park or neutral. I was also thinking about trans fluid and a filter because of this. I haven't done anything to it since it seems to be running ok at the time but I know I will have to do something soon The O2 sensors and fuel filter are a definite in the very near future.

Thanks for your advice, I'll have to check the plug wires and eger valve.

[sweetal]

Originally Posted by danielsaxxon

The Idle air control valve is new. The old one didn't like the colder weather here in pennsylvania. A few days ago I finished the tank of gas with the fuel injector cleaner. The car seems to be running ok now. The hesitaion was during acceleration when the car was under a load like going up a hill. It felt like a fish on the end of a fishing pole. When it started acting up it would do it when the car was under a load and also when slowing down to a stop. It never stalled. I thought about the egr valve but haven't done anything to it yet. Was also thinking about the fuel filter as well. It never seemed to hesitate or run rough when idling in park or neutral. I was also thinking about trans fluid and a filter because of this. I haven't done anything to it since it seems to be running ok at the time but I know I will have to do something soon The O2 sensors and fuel filter are a definite in the very near future.

Thanks for your advice, I'll have to check the plug wires and eger valve.

I had the same problem. Changed the fuel filter, air filter, and plugs (tune up) and hesitation cleared. I hope this helps. If not, could be more serious--hope not!

[sweetal]

another thought: how are your brakes? need adjusting--could they be gripping too tight? you probably would've smelled them by now if that's the case.

[superfret78]

Sometimes bad spark plug wires cause hesitation when under load. If I were you, I'd worry about doing a basic tune-up and include a plug wire and fuel filter change in that first....its cheaper than worrying about a bunch of oxygen sensors and will probably solve the problem.

[JR Tigerstar]

Try cleaning your MAF sensor also.