2003 Crown Vic surges and bucks when fully warm

To hmac300.

Did you read the question above? The engine light does NOT come on. The throttle plates were completely cleaned as well as the plemneum when the intake was replaced. I also stated the fuel filter was replaced. I guess I was hoping for a little more?

Sorry if I was short. This problem has been so hard to find and I hate the thought of taking it to some shop so they can charge me $$$ to tell me they can't find anything. The crank/cam sensor is a good lead and I will check into the fuel pressure. Thank you for you response.

Chris

Hi again,
Its been close to a month now and I did replace the crankshaft sensor even though the original one checked out ok. I installed a fuel pressure gauge to the windshield and its usually around 30-35psi. The car has been working fine the last couple of weeks and now again tonight, its starting surging to the point of having to park it. Once it is completely cold, it usually works ok for a while. During the surging the fuel pressure is still up in the 30 plus range. I am starting to wonder if its the computer? There is NO check engine light. The light never comes on when this happens. Any new ideas?

I truly suspect that your vehicle is running lean when it warms up. This can be caused by a variety of different issues. If it was in my shop, I would hook up a scan tool to see what the fuel trims are reading. These are what the PCM uses to determine fuel mixture. If there are no vacuum leaks, I highly suspect a mass air flow sensor concern. I know you stated that you cleaned it. Rarely does this ever solve a problem with the sensor unless there is actually debris on the "hotwire". The mass air flow sensor does much more than reading air volume; it measures barometeric pressure and intake air temperature- believe me when I say that they are important.

Thank you again,
I will check out the grounds as you mentioned. There very well could be a vacuum hose somewhere with a hole in it? You mentioned it might be lean when warmed up. I have gotten it fully warmed up and have run it several time from 60mph up to 110mph and it pulls strong. I think the injectors are ok. The mass air flow sensor could be a possiblity as well.I will keep digging.

Well guys, I think I may have found the problem? Still too soon to say. My battery light started coming on about a month ago. (I know my troubleshooting skills are not the best). The alternator was under warrenty, so they gave me a new one. The light would still comes on once in a while. When the battery light is on, the battery voltage with all the accesseries on is like 14.65plus, seemed too high? Whne the light was on, I wiggles the alt. Wires and the light went out. I took a closer look at the alt. Plug. About 4" back from the plug end, the wires had been spliced and one of the thin wires was broken. Someone must have spliced in a new plug end at one time and did a poor job with the connector. Anyway, I soldered them, re checked my battery voltage and its like 14.18 with everyone on and running. Went for a 1 1/2 hour ride both on the freeway and stop and go traffic, it runs perfect. Ran it up on the freeway to 112mph and pulls good with no surges ever. Like I say time will tell, but what a S.O.B. To find. I sure hope this was it.

Replied on May 6, 2013

Mine ended up being a dirty MAF sensor. I still have the original sensor in the car with over 182,000 miles on it. It needed to be cleaned with MAF sensor cleaner, not carb cleaner and that did the trick. $8.00 can.

As part of my troubleshooting you might want to try this because I thought mine was fuel related at first. I went and bought a fuel pressure gauge tester, it came with about 3 - 4' of hose. I duct taped the gauge to the outside of my windshield and left it there while driving everywhere for like 2 weeks. Of course, than it worked fine until one day while I was driving in hot humid weather it started bucking and surging. The fuel pressure was good, had nothing to do with it at all in my case. It wasn't until it happened a few more times and left me stranded in a parking lot that I decided to unplug the MAF sensor. Bingo! The check engine light came on when I unplugged it, but the car ran great! If I were you I would get a fuel pressure gauge so you can monitor that for starters. Good luck!

Thank you and drive safe.