i have a 1997 expy with the 5.4l 4wd and i have had to replace a coil pack befor and it is doing about the same thing. the code is reading too lean bank one. about two weeks ago it started missing and the check eng light came on and the code was missfire #4, drove it home and it quit and started running great and the light went out, now it started missing at low speeds. after the bank 1 problem i ran a tank of gas with lucas fuel cleaner in it and still no luck. it runs rough, misses and only runs decent when driving on the highway at 65mph and under no load but when i give it gas to speed up or go up a hill it starts missing again and still does it at idle. it has 138k miles and everything is the same as when i got it at 80kmiles except new plugs and a new coil pack. i noticed that there is a o2 sensor befor and after the converters so gutting them i think is out of the question. PLEASE ANY AND ALL INFO WILL BE VERY VERY VERY HELPFULL

 

Check that PCV hose!

 

ok we have an update for you guys, i have replaced the pcv valve cause when i went to pick it up from autozone i had then redo the check eng light test and now it comes up with bank 1 and bank 2 too lean and missfire on 4!!!!! so i bought a pcv valve and a fuel filter to see how that helps. here we go again

 

just installed new fuel filter and still no change HELP!!!!! HELP!!!!!! HELP!!!!!!

 

All of the codes you are getting are misfire codes (the lean bank means that too). I know because I had both banks lean and the local Ford service department said it was misfires. Did you change wires with the plugs? Also, what plugs did you use? You might need 2 new coil packs. Keep us posted.

 

well i have installed a new pcv valve and checked all the hose and they are fine. i also installed a new fuel filter. and now the problem comes and goes some times it will start missing at idle and driving and then sometimes it runs perfect for about 10miles. please help with any and all ideas!!!!!! thanks

 

Sounds maybe like coil packs, but which plugs did you use and also did you replace the plugs wires?

 

I'm assuming you have coil-on-plug ignition (5.4 has it, 4.6 doesn't).. I would try switching the #4 coil with one from another cylinder (preferably from the other side of the motor) to see if the misfire migrates to the other cylinder... if it does, then you know that the coil is the culprit... If the miss stays at #4, then I would try another plug in that cylinder (#4 is very easy to crack just because of it's crappy location)...

 

it has the 5.4l v-8 in it and when i replaced the p[lugs last time i used what autozone recomennded i think it was motocraft or something like that, i know that it was not the cheap .97 cent ones it was more like 1.5002.00 each. thanks for the advise, i wont be able to try switching them around till thursday and then only if the rain holds also. expy to big for me old turn of the century model-a garage lol!!! i will besure to keep evryone posted asfor the results!!!

 

Too lean could mean many things. I believe that the stumble under load is definately related to fuel injector or plugs/coilpacks. But, since you have the "too lean" code, I would look at the fuel injectors first. If only one bank is running lean and its stumbling, I'd say you have a fuel injector not firing properly. Probably just one too. It may be worn out or you may have a loose connector. Use a stethascope and listen to each one fire. See if one sounds weak.

Another thought is the MAS. The MAS (mass airflow sensor). I pulled one out of a friend's Explorer today and it had a dead ladybug stuck to the thermistor. He said it had been running rough and crappy for weeks with no codes though. We cleaned that and went ahead and cleaned/lubed the IAC and throttle body as well. It runs like it did brand new now. If you have never messed with the mas let me know and I can walk you through it. Basically its a pair of thermistors, one hangs in the airflow tube and one is tucked away behind a shield. THe trucks on-board computer compares the temperature readings off of the two sensors and determines the amount of airflow based on that calculation. If the one that hangs in the airflow gets dirty or gets a dead bug on it, it gives false readings and you run too rich or too lean (this affects both banks however). Even if this isn't the problem, it should still be cleaned every 20k miles or so.

 

Have you checked the rubber elbow in the back of the engine for a vaccuum leak? It tends to rot away after a few years. Bank 1 and Bank 2 too lean are an indicator of this. This is where the PCV valve gets it's vaccuum source. It is a common problem and takes a couple of minutes to check. Also, a very easy and relatively cheap fix. Not sure about the misfire, but before I invested anymore money and time, I would at least do a quick check. Good luck.

 

That makes complete sense. I changed my plugs and forgot to reinstall the pcv valve into the valve cover and then my check engine light came on. The error codes were that Bank 1 and Bank 2 were too lean. I had no clue that the codes were for the PCV Valve but now, after clearing the codes, no more check engine light. Thanks jprop!

 

i am going to take a can of break cleaner to all of the vacum lines tomorrow and also check each injecter by taking the auto steth to each one a listen to them, i had no idea that you could do that, thanks for the advise. will let you all know how it turns out!!! cross your fingers for me lol

 

ok, i placed the number 4 coil on the number 1 and vise versa and the check eng light came on stating that the number 1 was missfiring change coil pack problem solved. changed pcv valve and no change, checked the hose for it and found that in the back it was rotted almost inhalf, while trying to remove it i broke the acual hose and a few min. at autozone with a new pcv elbow and a rubber splice of hose i was back in business. now all the problems are gone and she runs like a bat out of h e double hockey sticks!!!!!! thanks to all of you guys that replyed in my time of need. thanks so much for all of your help!!!!!!! john g

 

OH YEAH!