I have an 03' F-150 with the 4.6. Everytime I am coming to a stop (especially at slower speeds) I feel slight shuddering in the idle. Not a violent shudder, but is very noticeable in traffic. I have no codes being thrown or any stored data to help me pinpoint the problem. I recently have been bringing this truck back from the dead because the previous owner showed gross negligence in the routine maintenance department. So, I've cleaned the maf, throttle body, and iac. Also installed new plugs, and cop's. I have also done two oil changes because oil was black as death and changed diff and transmission fluid. The truck has a 4" lift on it and some fairly large 285/75 r16 tires and is absolutely gutless. I will restore some power back to this truck with e-file, underdrive pulley kit, tuner, larger trans cooler, and possibly an oversized radiator. However, I need to eradicate some problems first. This being one of them. Anyhow, this is my first post and I certainly appreciate any thoughts on the matter. Thanks

 

If you intend to keep the large tires, the tuner will bring some of the life back into the engine. The rest of it you won't know you did anything to it. I wouldn't waste the money. The biggest bang for the buck will be changing the rear axle ratio. Most likely it has a 3.55 axle. You need to move to a 3.90 or 4.10 and then it'll be only reasonable. It still won't be a hot rod. The 4.6 is a great LITTLE engine and can last a long time but it'll never be a power house in that truck. In regards to the idle, I'd try adding a bottle of Techron to a half tank of gas and see if that improves the idle. The notation of the oil being black means the engine is struggling to pull the truck and carbon deposits will be yer friend under those conditions. It may take a few doses to clear it all up. So to eliminate all of the issues, you're looking at changing the rear axle ratio or putting the 255/70/16 standard tires back on it. The truck will look better if you can find acceptable 265/65/16 tires though. They will be a bit taller than stock but won't hammer it near as hard as the 285/75/16 you currently have.

AS a FWIW, assuming you have some idea about the trucks previous life, the O2 sensors should be changed at least every 100,000 miles or sooner. The upstream sensors feed info to the ECM which regulates the amount air/fuel needed. If they are on the edge of the range, it can cause issues with idle and poor fuel mileage. There will be no codes. Use only Motorcraft units as aftermarket brands are not always compatible with the expected heat cycles of the ECM. It will give you a headache chasing a light miss. Same with any of the emissions parts like the PCV, spark plugs,etc. Motorcraft only.

 

Thanks for the heads up labnerd. I bought the truck with the lift and tires. It's the third f150 I've owned. I've had a 99', 02', and now the 03'. All three had and have the 4.6. Each had their own little quirks. This has the most little b.s. problems of them all. Oversized tires, 4" lift, and stock gears with the small motor = gutless pig! Anyhow, I really love the way this one looks. I'm a keeping it! So I gotta make the best of things. But, re-gearing the 8.8 rear end is quite an investment of money and time. My boss has a tenant with a large amount of 9.75 rear ends waiting to be built. I am told I can have at one of them for a couple hundred. I believe would be a more reliable and bullet proof platform to gear up. Must way out this option carefully. And I also own the efan and underdrive pulley kit. They are just waiting to be installed. Kids and being on call 7 days a week have been killing those projects. Trans cooler is an easy and cheap pull at the junkyard and 100's to choose from. The tuner I am looking at is fully carb compliant. These items will help free up my lost ponies. But, not give asphalt roasting power to my oversized under powered piggy. I really need to knock out the shuddering upon breaking at slow speeds. It even studders on the freeway between 55-70 miles per hour. I can feel it on the gas pedal. So, I think I'll take your advice and change out the primary O2 sensors. My buddy Howard whose a mechanic at Kearny Pearson Ford said replace the iac as well. He can see in there system notes that they were problematic between 02-03'. And also said cleaning it could even make it accentuate the problem. He also said I gotta spend solid time looking at all vacuum connections and hoses. I got work to do I suppose. And yes I know all too well to go oem motorcraft parts only. Ford engineers use these parts for a darn good reason. I really appreciate your time and thought. It's cool to have a Ford support group.

 

I just spied my problem. Number seven cylinder has slight amount of fluid or wetness around spark plug probably causing my misfire. Looks like the crossover tube gasket for the thermostat housing has a leak. Probably a leak at the intake manifold as well. Gotta replace them. As soon as my parts arrive and I get this fiasco knocked out I'll post pictures. I have to button everything back up tonight so I can drive to work tomorrow. Anyhow, needed to share as I am sure they'll be some similar experiences. Probably even some with oil in the cylinder rather than coolant. I had to look up the name of that gasket. Knew it was thermostat related though.

 

Great day yesterday! Earlier on in the week pulled my transmission off the truck and was able to inspect a bit. Had a cracked flexplate and a blown torque converter. Replaced them both this week. Buttoned it all back up yesterday. Very long week. But, the truck runs great and no shuddering. Shifts are much cleaner. Also at the last minute I decided to replace the crank position sensor which kept getting oil collection on the wiring harness. I cleaned it up three times in the past 4 weeks and still had oil collecting on it. Replaced it and bam!!! Lost power back! Accelerates like a brand new truck almost. Very happy day. Have owned this truck for 4 months and thrown $3200 into it aside from purchase price. Anything and everything that could have been a future problem is crossed off the list now. Woohoo

 

thanks for reporting back.
what led you to the transmission? was the TC leaking? Explain more on "Blown", please

 

Well, to be quite honest I was grasping at hairs. I had done double fluid change on the transmission shortly after buying the truck. And the fluid looked smoked all over again in just a few months. And I had crossed misfire off the list due to a spark plug and coil replacement. Crossed vacuum issues off by replacing all vacuum hoses. Replaced all O2 sensors. Did the catalytic converter test. No blockage there. Replaced fuel filter and soaked the injectors, along with running the fuel system through my buddies fuel cleaner machine. Cleaned and inspected the maf, iat, iac, and the entire throttle body. Pulled the silencer in the intake and adapted the inlet to up air volume going in. Split oil filtration into dual filter canister to ensure clean oil flow. Mounted up a trans cooler from a super duty ford making sure trans was staying cool. Put on my e-fan and underdrive pulley kit to beg the truck to gimme my horses back. Then I continued to read and research the shuddering since I was lost. Torque converter was the only thing I could find that would draw my symptoms and not throw codes. So, I nutted up and pulled the transmission. What a pain in the *** by myself. Never again. Anyhow, I could see fractures in the flexplate. I knew I was having rock hard shifts and something else had to be wrong because f.p. wasn't in pieces. So I pulled the torque converter and it was full of smokey fluid. I just decided to replace it along with the flexplate. Had high hopes. So, I took it to a Ford dealer I regularly work with. My fleet mechanic Howard inspected it and claimed it bit the farm due to age and neglect of transmission services. I believe he said it wasn't releasing anymore? That made sense because the yellow plug was in the pan on my first change when I bought it. They never changed the fluid (130,000 miles) Having said all that...replacing those and the crank position sensor changed the whole driving experience. It truly feels new. Pretty exciting to just relax and drive now. Not searching for problems is good

 

Late to the show but you confirmed my suspicion it was the Torque converter by the way you described it.
The diode function was not releasing and keeps trying to move the truck against the brakes.
You have to like that truck to do that much investment.
I am at over 270k and see no end yet. The 4.6 motor is still super with lots of power. Had a higher stall converter installed and sure made a big difference off idle acceleration compared to stock. No difference once the converter is locked up in cruise.
Good luck.

 

Wow! 270,000?! You got twice the mileage I got on mine. That's either testament to a well built vehicle or testament to the owner's service vigilance. I assume it's a bit of both. That's really cool to hear. Aside from that I put the B&M racing holeshot 2400 in as will not be doing that service again I hope. I do like this truck, but I am more or less stuck with it for now. I sold my Titan 5 months ago and bought my wife a new car because her transmission was going in her SUV. I was afraid she'd brake down with the kids in it in summer heat and I'd be stuck at work not able to help. My Titan was my baby. Most excellent truck ever. But, I have struck a new relationship with my Ford. My love has grown for her. At any rate, I am sick as a dog from overworking myself. Between, all hours spent at work and overnights working on the truck..... I am literally broke, sick, and tired. I got the flu. Oh well back to work in the morning. One day off hopefully helps. Thanks for the words.

 

So, I just joined the forum tonight to ask about my 02 4.6 vibrating at idle and then found this thread, I'm concerned that this may be my problem as well. Is there anyway I can check the flex plate without pulling the transmission? The vibration has gotten Worse within the past weeks and I've thrown alot of time at it. I feel it in the whole body of the truck and majority underneath the cab at idle and now at lower speeds, no codes and torque pro info looks great so I'm leaning toward mounts and flexplate now. Any help would be appreciated.