Hear I am, all excited to get the L back out. I put insurance back on it and my new plate. Fire it up, run out the the gas station and fill up on premium (same station I ALWAYS get my fuel from). Well, I drove easy there. I got on it when I left and it didnt feel all there. So I set the cruise and headed for work. Got into town and did some hard excelleration. The performance was sluggish and the exhaust note was that of and old John Deer. I had some time so I took off out of town and got it into OD ans started easing into the gas. Before I was out of the Vaccuum side of my gauge, it started chugging like a mad. Felt like it was goning to rip the rear end right out from under the truck. I let off not knowing what to thing. Turned around and went back to work trying to reproduce the condition in every gear. As the gear (ie load) went up, the amount of pedal needed to reproduce this miss/chug was less and less.

The next day I got out the predator and looked at injector pulse widths, O2 sensors, maf volts, engine temps, throttle position, fuel level in %, etc. Everything looked good (I have watched these alot when I was running super lean and know what they should be). I have no codes, No engine light. Fuel filter has maybe 4k miles on it. Plugs are Denso IT 22s that went through a period of 16+ to 1 a/f before I got to dyno last summer. But when I parked it for the winter it was fine. Started it 4 times this winter and it ran fine. Idles great and cruising and very low throttle is fine. I thought maybe it was spark knock (last dyno was 11.6 to 1 at worst in 50 degree weather). So I added 10% fuel. It still did it (15 degress of timing on #4 pulley).

Anyone have an opinion? Im thinking plugs or injector or coil. If its a coil, I sure wish I knew which one it was.

Chris

 

You can find out if it's a coil by cranking her up, then pull the wire from one coil at a time, if the miss gets worse, the coil is good, if it stays the same, chances are you found your prob.

 

the problem is it idles perfect and free revs fine too.

Chris

 

Beats me, gotta be some sorta ignition prob or fuel prob. How many miles on the truck? Fuel filter?

 

I was running denso's it-22's with 1200 miles on them my lightning started missing i had two denso's plugs with tips burnt off no more denso's for me TR'6's for me from now on/

 

make sure somebody dindn't swap out the 5.4L for a john deere lawnmower engine

you said it sat over the winter. how much gas was in the tank? how many miles have you put on it since filling up?

 

sat over winter with 1/8 tank for gas. No stabil added. I did add some dry gas to it when I stored it. After I filled it up and the problem started, I added another bottle of dry gas and it sat 2 days. Today I drove it and the problem is getting worse. Now cruising at 55mph, I get a slight miss (enough to feel, but not bad) and now when at a stop light/sign idling I can feel it pretty good (although its not constantly missing, just here and there).

Fuel filter has approx 4-5k miles on it and has been changed every 8-9k miles since I have owned it. Truck has 38k on the clock. 75 miles since fill up.

Chris

 

Don't forget to clean the IAC valve and posibly the MAF meter. My truck has idled fine but would make it out of the drive way with the IAC dirty.

Peace,

Suavy

 

suavy, what should i use to clean the MAF? Carb cleaner ok for the IAC?

Chris

 

Sounds like dirty injector(s). Sitting allowed all the crap in the system to settle. Now it's trying to squirt through the injectors. Replace your fuel filter. Buy a couple you may have to replace it again.

 

Chris, pull the MAF off and check inside the sample tube. Make sure a spider hasn't taken up residence there.

Don't laugh, I've seen it many times.

 

Fuel filter. Exact same problem on my truck with almost a year of frustration until i got it figured out...

 

tomarrow i will do the fuel filter and check the MAF.

I think I will try some plugs too. They cant be looking to well after 16+ to 1 a/f from last summer. This will also give me a chance to test each coil (assuming I can dig up resistance specs). Should i try the NGKs this time? Which NGK for a #4?

Chris

 

First thing I would do is change the plugs with the nap its had. If the problem still isn't corrected change the fuel filter. Hopefully the problem is gone because if it's not I'd bet it was a bad coil pack, and those things suc to track down. Good Luck.

 

changed the fuel filter and it still does it. time to look at other things.

Chris