My wife's 2003 Expedition (4.6lt, 2wd, 80Kmiles) has recently started what I always refered to as surging (cruising along at say 40-50mph...that is where it is worst, and the car will lurch a bit). It also seems to miss like this at idle. The truck sure seems to have lost a lot of it's power. The check engine light didn't come on for a while when this first started (few weeks ago). I attributed it to maybe bad gas, or fouled plug, or bad coilpack. Then the engine light came on for a bit, then went back off. I took it to be scanned and the scanner read that cylinder 5 misfired. I figured at that point it was likely coil pack.

I figured while I'm at it, I'd do plugs, so I pulled the plugs and replaced the coilpack on #5. the plugs all looked lean to me (whiteish). Thought maybe it would be a good time to replace the fuel filter and that maybe it was bad enough to be causing this. Swapped the fuel filter as well, but alas, its still doing it and maybe getting worse.

So, with all of that said, where do I go from here? Injectors? CPS? TPS? What else can i check to help diagnose this?

Thanks all!

 

I had a heater hose leak that caused the same problem. There is a tee for rear heater that dripped onto 2 front plugs pass. side, very slight drip.

 

really?! very wierd but worth checking. I don't see anything under the truck except a little oil leak that started after my last oil change. I have to address that too. They couldn't be related (oil leak and my issue), right?

jsut remembered, cylinder 5 is the driver's side front cylinder and there aren't any wet hoses there.

 

change the oil yourself and you wont have leaks, my coolant leak was so slight not even the dealer noticed it, they do all my service.They replaced the hoses & plugs wanted $734 dealer said it was a maintenance issue and warrantee would not cover.Since they do all my service, I took 2 pair of boxing gloves out, made a challenge and they decided to give me 70% off. Keep us informed of your progress GOOD LUCK

 

LOL (on two counts). I did the last oil change and at the boxing gloves comment.

If there is nothing wet near #5 and that is the cylinder that showed a misfire, what would that be besides coilpack, plug boot/spring, plug?

 

just found this....

" work at a dealership, my Expo did it also. There is a TSB reguarding this. It ultimately has to do with fuel tank slosh. Replacement of the fuel pump is usually required with a new one per TSB. I cant guarantee this will fix your surge, but it did mine with the exact same problems most of you have. I would take it to a reputable dealer and let them know what you found. Dealers have a hard time diagnosing this problem due to fact it is an intermittent problem. My ford website is down, or I would give the TSB #. Remember that if you want to do this yourself you will need the p/n for your vehicle application, do not replace with aftermarket, get the Ford pump listed in the TSB, per application."

from post https://www.ford-trucks.com/forums/4...n-surging.html

sounds pretty dead on...lean plugs, same speed range, same same.

Dealer wants over $700 to replace the pump! ug. I'll start a new thread asking all of those questions.

 

well, I pulled the crank sensor last night thinking that might be the issue (before I read that post on the fuel pump/tank slosh). NAPA gave me a CAM position sensor instead, so I had to put the crank sensor back in. I cleaned it really good first. Hmm..what do you know. Truck ran really good last night. Could a dirty, grimy crank position sensor cause a cylinder to misfire and hence my problem?