98 Expy 5.4, misfiring in low RPMs for 3 weeks and not showing a single code
 

For whatever reasons, a lot of forum regulars choose not to lend their advice to "noobs" like me, but I figured I'd throw my line out there anyway and hope someone will give some helpful knowledge.

I have a 98 Expy, 4x2, 5.4L with 265,000 miles on it (no major repairs or rebuilding ever, just routine maintenance :)). For the past few weeks, around the first ten to fifteen minutes you drive it (goes on well after the temperature gauge has reached normal temp) it misfires, skips, whatever you want to call it under light throttle, below 2,000 rpms or so. Occasionally idles rough when this is happening and you let off throttle, but not always. When I manually downshift it and it goes above 2 grand, the skipping goes away. The nature of the skipping under throttle is sometimes so rough that it jerks the car like the engine is cutting on and off when you're trying to make it up a hill.

Now, I would normally consult the handy dandy code reader, but it shows "Pass, No Codes", and the CEL does not come on whatsoever, and has not come on at all in the entire three week period that the car has been doing this. I know the bulb is not burned out because it comes on for a second every time you start the car. It's been tuned up in the past 50,000 miles with double platinum plugs and the rubber boots, but not all of the coils were replaced. I thought it was one of the coils, but whenever one has gone bad before, it's always made the CEL come on and flash on and off, and showed misfire codes.

Please help, my family has had this Expy for almost 9 years and put over 200,000 miles on it, been through 30 states, it's been the most reliable vehicle ever and we plan on keeping it until the motor or tranny goes, then rebuilding them and drive it some more! I love this car and want it to run like it's supposed to, but I don't have the money to take it to a Ford dealer to figure it out, nor would I want to chance one of their mechanics treating it like a brand new car and throwing a rod in the poor old Triton...

That's a load of bunk, around here we try to help everyone and anyone, except maybe people with attitudes! The problem with "noobs" is they will usually show up out of the blue and ask a question that's already been posted and answered 27,000 times; instead of taking the time to use the search feature.

For your issue, disconnect the COPs one at a time until you find one that doesn't change the way the engine idles. When you find one, that's the problematic cylinder. FYI, disconnecting the COPs will turn on the CEL, but it will reset at the next key off/on cycle.

i am having the same problem. i would think there would be a error code if a cop was bad. i have had 1 go bad and a code came up right away i changed it and ran like new. mine is a 1999 navigator with 170,000 miles. seems like a fuel issue to me. my fuel filter is new. don't know about the fuel pump. dont know why there are no codes with the truck running so bad.

finally someone with the same issue. im definitely interested in your findings. i also had the pack pull down but that didnt work for me, so id be interested in your findings.

i did some more searching and 1 member said that he feels it would be the COP even though no codes. he said would have to be a bad missfire to cause a code. mine is kinda bad but also kinda intermitent. runs better some time and worse other. i noticed on at least 2 COP's the mount is cracked so slightly loose. i think i will order the china COPS and see what happenes. dont wanna do the fuel pump :( bought a new fuel filter any way so will do that first.

Our 2003 5.4l had issues with 2 COPs for a few months before it set a code. It first started with an occasional misfire at idle, then roughness under light acceleration. It would smooth out above 1600 RPM. No codes were set. It would get a lot more frequent when it rained, then clear up a bit when it dried out. It kept getting worse until it would idle very rough and a code was finally set. Turns out the firewall insulation was misaligned when installed and got stuck under the plastic moulding at the base of the windshield. Rain would drip down under the insulation and drop on the #6 & #7 COPs. The codes were for misfires on 6 & 7. The springs in the COPs were all rusty from the moisture. Found the leak by running the garden hose on the windshield. Changed the 6 & 7 COPs and it ran great. Changed them all after that.

well thanks for the post. sounds like im getting somewhere. my symptoms are the same so i am going to order the COPS and will post when i find out if it fixes the problem. crossing fingers :)

Almost guaranteed to be COP #4 near the passenger side firewall. Water gets in and does its number over time. pack it with dielectric grease to stop future problems. Also, go ahead and replace the plug while you're at it. Also, not a bad idea to go ahead and pack the other COPS with grease too.

thanks for the info. no 4 is the one i did already some time ago. so must me one of the other 7. think someone mentioned 3 and 7 due to a leaky hood trim. probably start there. im gunna order the 8 from e-bay for the 100.00 or so. will leave me with 1 extra in case one of the cheap one fails. thank god for this web sight saves us poor people from getting screwed by mechanics

Recheck #4. i replaced the same one 3x before my cousin told me about the dielectric grease trick. The stealer really screwed me the first go around.

Don't forget sticky injectors can cause misfires... free up for a bit, then get sticky again... etc...

I'm trying to get to the bottom of the same issue except all 8 cops and plugs are brand new... Hoping some real lean (injector cleaner laced) gas sitting in the rails / injectors for few days will help free them up...

I'll get 308 and 300 codes, clear it & get a 303 the next day ~ which is why I know it's injectors ... That plus the car had been sitting for 12+ months (with who knows what, in the fuel lines)

BUT I must say, I can't pull codes driving around town... I have to get out on the open road @ 45mph+ for 5 minutes or longer... *** And it won't turn the CEL on either... The computer picks it up but no solid CEL.

you may have some varnished gas in lines from sitting. 1 year is boarderline for gas to go bad i add gas additive to my boat for the winter storage. may be worth me trying some injector cleaner before switching the cops. maybe run the truck low so the mixture will be more concentrated. seems like the problem is getting worse and worse. i am hoping i get a code to determine the cylinder with the miss. im tired of fixing all the time wish i could get a new truck. all in all the truck has been good to me

got the new COPs from ebay 130.00 ish. i was going to put them in 1 by one to figure which was bad if any. did one this way and said frig it and did other 6. the no. 4 was new last year so left alone. did use grease and low and behold missfire gone. so you can have a bad COP and no codes to be read. my symptomes were exactly like lincolnboy73 described. running fine now. im going to save the old COPS in case any of these cheap china made COPS go bad. I have 1 more new one to use so i should be good for the life of the truck. 170,000 and running good (knock on wood :)) thanks for all the help from members. great site for do it yourselfers

Did any of you have a gas smell at idle with this? 05 expedition 5.4 same symptoms but with gas smell through vents at idle.

With the smell being that strong I would suspect a leak.