This is not a very uncommon problem in many ways with these F-150's but I need some more opinions for some un-conclusive research with the problem that I have.

3 days ago I purchased a 2006 F150 Lariat edition with the 5.4 liter engine, with 192,000 on it directly from a Ford Dealer. The mileage was something I wasn't too keen on, but after talking with the sales guy and him showing me some of the maintenance records he had on it....I went ahead and purchased it. The dealer had supposedly sunk a decent amount of money into the truck before putting it on the lot. The cats were replaced, the plugs were changed, and the #8 coil was replaced. The sales guy said when it was brought in, it had some jerking issues when driving but it was fixed. When we test drove the vehicle we didn't notice any issues.

I drove it home (about an hour drive) completely fine, but the next day I got up to drive it and the thing was shaking/hesitating/misfiring like crazy. Classic symptoms of what seems like a coil or spark plug issue with these engines, misfires/hesitates around 40-50mph, stops once you turn off the overdrive. I took it into my local mechanic, who said it looks like none of the coils were replaced, and none of the spark plugs were either. I took his word for it, and went right back to the dealer I bought it from to have them reassess what they supposedly done to it.

I am having it checked this upcoming Friday, but I will probably end up doing the work on my own if they will not repair it. NOW I am a newby, and I am in no way an experienced technician, but I borrowed my buddies bluetooth OBD scanner to track some of the vitals of the truck, and the results I got from the scanner are very inconclusive and I need a little insight. On average there were only 30 misfires within the 45 minute drive I was observing the technical details (to me that doesn't seem too crazy). What is striking to me is how the fuel trim and O2 voltages are running. The fuel trim is bouncing all over the place (never steady or slow adjusting), and the engine is running very rich overall. The O2 sensors are all over the place sometimes even zeroing out for periods of time. My overall looming question, is this a coil/spark plug issue? Is it worth spending several hundred dollars to get all the parts if it won't fix the issue? I've read a lot of posts on this site that say the same thing, changing coils/plugs doesn't always work. The readings I was seeing on the scanner scream to me that I have another issue (like an injector) I need to look into or have my mechanic look for.

 

what were the codes that are recorded ........ that narrows it down somewhat. If its isolated to one cylinder, replace that COP and see what happens.

 

I had the same jerking at about 45MPH and 1500RPM. I replaced all plugs no coils and truck runs great. Could be the sensors are all over the place trying to compensate for the misfires. When I restarted my truck after reassembling after plug change it ran like crap for a minute and smoothed right out. If the salesman told you plugs and a coil were replaced and they weren't, I would have the dealer make it right somehow. I don't trust any dealers around me to work on my truck outside an oil change. Even that is questionable sometimes.

 

Replacing my plugs and COPs seemed to solve a similar issue I had too. Recently mine started SERIOUSLY sputtering, like barely running, and so far it appears to have been a faulty/old battery. 10 year old battery, the original. With a new one, runs like a champ.

 

I recently got Gibson Proformance Headers on my 2006 Ford F150
And when you cold start it or just start it period it has a odd ticking noise on the passenger side HELP ME!!

 

My take on this is - SLOW DOWN. Take @steve(ill) 's advice and get codes, pending codes, and study up a little more on OBDII and these Forums. Your post screams another fellow Ford owner is fixing to throw lots of $$$$s at a problem with very little success.

First: 30 misfires within a 45 minute drive IS (very crazy). My scanner (OBDII Mode $06 Test Results) reports ZERO misfires in the current or the last 10 Drive Cycles on my 2004 5.4 with 216,000 miles on it.

Second: O2 sensor readings are SUPPOSED TO BE all over place on the upstream sensors! (Not so on downstream which should settle down around .6 - .65 v when NOT under extreem operating conditions). You didn't mention which you were referring to. These are best monitored on a Graph. Be very cautious about jumping to conclusions (or taking advice from parts counter sales people, or anyone who jumps to conclusions) on single OBDII readings - or DTC codes for that matter.


Third: Fuel Trim readings are also VERY dynamic and as you say "bounces" all over the place as conditions, and especially engine RPM/load changes. That is normal. It is the PCM responding to rich / lean readings from the upstream O2 sensors. What do you mean the "engine is running very rich overall". Many OBDII readings, such as Fuel Trims, are interpreted incorrect - even BACKWARDS. Do you mean the fuel trims are generally "very positive"? If so, that means it is running "lean" (as normally stated) which is based on the O2 sensor signal requesting more fuel (longer injector pulse widths) to achieve the proper air mixture. THAT would not be indicative of a COP, or misfires - which will cause the opposite effect. As will an injector ---- leaking, BUT not plugged.


So what I'm saying, you need to try to get lots more GOOD, RELIABLE DATA before making a decision. OBDII diagnostic data is not a silver bullet and need to be taken together with other sensor data/symptoms.


I'm not beating up on you, just hoping to help.
Best of Luck