I have owned this truck for three yrs . It has 130k miles. The history: 2 months ago the motor stumbled as it would if you run out of gas. I removed cat and changed fuel filter (filter was plugged. I couldnt blow through it. Had to be 15 yrs old.) Ive just been looking for an excuse to remove the cat. All symptoms were gone until i got 1 mile from home and it stumbled again but cleared up. I drove it to work and back for a couple of days and then the stumbling returned. I dont have a guage to check fuel pressure so i changed fuel filter again and now i only use rear tank. If i switch to front tank i get the stumble again. Obviously front pump is dying. I havent had a problem until 4 days ago when we finally got substantial rainfall. The motor runs rough all the time cold or hot. sounds like ignition. This motor runs exactly as if a plug wire was failing. It has a constant miss all the time low rpms high rpms. It still has decent power but not like normal. I upgraded from the carquest cheap stuff to autolite plugs and wires, also accell cap and rotor. No change whatsoever, just 80 bucks broker. I did the self diagnosis code retrieval with it and got two codes 33 and 133. I replaced all of the larger black air lines ( the ones located all around the throttle body. you know the ones that rot and leave black residue on everything that touches them) I checked for any loose or corroded electrical connections. Input voltage at the coil is 12 amps. I dont know how to check the coil but it would seem that if the coil was bad it would miss in a different manner than it does. I dont have a scanner or plug testers or fuel pressure guage. I just have wrenches and an open mind. I cant find any posts on here that can help me, so somebody help me! sorry this is sooo long but I know if i dont explain everything that i will get a lot of ideas that ive already tried.

 

Code 33 is an EGR not opening error
Code 133 is an O2 fault error.

those both can be an actual failed sensor or an actual true condition caused by air leaks or poor fuel pressure

usually you can rent or borrow a fuel pressure tester from an auto store

You didn't state the year so do not know if you have the two fuel pump dual tank or the 3 pump/reservoir dual tank setup. You state you have a bad front tank pump and it can interact with the rear causing low fuel pressure depending on the year.

 

The computer will display either two or three digit codes, but not both. Ford started transitioning to three digit codes in 1992. We need to know the model year of the OP's truck to figure out if it should have two digit codes or three. Right now the test results are invalid.

 

This is a 1996 f250 4wd. Regarding the codes..if a sensor of that importance was faulting wouldnt the cel illuminate

 

Your truck should display 3 digit codes.

Many times there can be a faulty sensor or other issue without turning on the CEL. That is the reason why we always suggest to start by checking for codes. They can eliminate a lot of guess work, wasted time and $money$.

 

After reading a couple of other posts ive learned how to self test with KOER. im getting a 4-3-6. my code listing doesnt have a 436. any ideas? by the way, all of yalls help is very important to me and very appreciated also. ive been laid off for 6 mos

 

Here's something you might want to check.......the in-dash tank selector switch........in may be on it's way out.

Just an idea for you.

Bob

 

i dont know if this would be a testing method but when i switch tanks, i can hear the difference of one pump stopping and the other starting. one sounds very crisp and the other sounds like its dead. yea ive been through that debokle with my 87 in 89. i really need to get a fuel pressure guage

 

check that code that i previously posted. it seems that it is giving me a 536. i checked it three times and all three times i got a 536 code. my code chart does not have a 536. any more help? oh yeah KOER

 

ok this time i did the KOEO and KOER test correctly and the only code brought up was the 111 for both. i understand that this means all clear. back to the drawing board. thanks again for any help. i will post anything i find out of the ordinary. you will know if i cant find it, i will be on the nightly news

 

Not sure of what to make of the above in bold.......


You still could have a failing (not FAILED) tank selector switch though.

Bob

 

Does it run equally bad on both tanks?

 

well, to trucker, before i turn the key and tank selecter is on rear, then i turn the key and hear the fuel pressure up, the rear tank pump sounds nice and quick, but if i switch to the front tank and that pump kicks in, it sounds more like i have a completely dead battery. i cant spell what it sounds like but there is definately a difference in the two. the rear sounding as they all do but the front sounds like it has about 1 volt going to it.
the answer to the other question is that it stutters when on the rear tank and after about a mile of driving with the front tank it still stutters but the if basically feels like its running out of gas and stuttering. yes i have about a half tank in each of new gas.
what i did last night was check all vaccum hose pretty thoroughly with an air gun, either, and visual. i double checked for any arcing or grounding of the plug wires. tonight the first thing is to double check the plug wire placement. the problems started before i changed everything but a crossed new wire could take the place of an old bad wire. ive never messed one up but theres always the chance. it would seem that a couple of crossed wires would run worse than it does. after that i will unhook every electrical connector and clean just for giggles. thanks fellas

 

i have positively ruled out any crossed plug wires. sprayed about a half can of either around any vaccum lines, throttle body, plentum, and egr connections or gaskets. its not feeling like its a vaccum leak, but one thing i did notice is that it (rough running) clears up at about 1500 rpms.

 

And when you sprayed ether around the throttle body, did you spray it around the TPS and then on the other side at the throttle linkage, namely where the throttle shaft is on both sides of the throttle body ???

Still thinking,

Bob