Our 1998 Ford f250 4.6 idles fine, but when on the highway at running speed it misses really bad. we just had new heads put on it and a new plugs and wires. we are at wits end. Not sure where to look next. Changed the fuel filter. Also there is a vacuum hose coming off the transmission that we can't seem to locate where it goes.... someone please help.

 

Just out of curiosity, what brand of plugs did you/ they install?
Are you sure it's a vacuum hose and not a vent hose?
Did anyone check to see if the plug wires are installed for the correct cylinders?
I believe the engine uses the waste spark system and if not careful the wires could be on the wrong plugs and the engine will still run , but can give the problems you are seeing. Look for any cracks on or around the coil pack.

 

Once again, Hanky, I'm impressed with your accuracy of suggestions. Also, why were the heads off? And addtionally, if you can scan the codes and retrieve your PO30x, where 'x' represents the clyinder misfiring, check the base eng. compression of that cly. verses anyother one that's NOT missing. I have a bad feeling about this...

 

One other thing. The transmssion doesn't have any vacuum lines to it, as it's totally electronic. It's the breather hose that comes up the top back of the bellhousing to the top rear of the engine to allow the trans. to breath and not ingest water.

 

we had to get another engine, when we got the engine the exhaust bolts was rusted and broken. a so called mechanic.... said he could drill them out. i am not a stupid woman and grew up with back yard mechanics (brothers). i doubted him from the beginning. anyway thats a new court case. we had a verbel agreement it he broke it he buys it. the guy drilled threw into the water jacket there for we had to get used heads. one came off of our old engine which had 200k miles so i bought another head. took both to the machine shop and had them worked. my husband put them back on torqued down to specs. he took his time. three times we have went over the firing order. the plugs we installed was motorcraft plugs.... and new wires. the egr vent tube has been replaced. omg we have replaced almost everything in it . trannie has been done. only thing i can think of is fuel injectors or sock on fuel pump. im tired of guessing and want to get it on the road before snow starts flying.

 

we changed the coil packs... as i stated almost everything is new. trannie , torque converter. alt, i am a gm person my self. i used to work on my own car. i have learned alot about this truck . we only paid 250 for the truck to start with. now i have invested over 2500 in it. it is so close to be on the road. as i stated i idles like a new vehicle ... pull out on the road its one sick sob. lol

 

not sure if its a vent hose or not. i will crawl under it tomorrow my self. my husband is getting so aggrevated.. says it should be an ole 350 lol.. i am thinking he told me it had some type of connector on the end but i will go under it and check ...

 

can advance auto do the reading on it or do i need to take it to a ford dealership?

 

Pretty sure if Ford does it , you must pay. Know Autozone does it for free, not sure about Advance. Why not just make the phone call and ask Advance ? These are all good P/R moves (public relations) and it helps keep business coming back. If you do decide to call could you let us here know, thanks.

 

LOL our local Advance knows me by first name and know my phone number, that tells you how many times in have been there lol. i did purchase a meter yesterday, got several codes P0102 MAF or VAFA which im not sure what that is. i do know the mass air flow. im not giving up till i get this truck in top running order.