Alright so I finally get the truck together and am not only plagued by horrid vibration but now my engine is miss firing (or so it sounds) like something horrible.

It can barely stay idling, all I hear is it running smooth then a loud 'pop pop' or 'pop pop pop pop'. then when I give it gas it does the same thing except much faster and has no power what so ever... until it makes it to about 2300, then it's like there is a flip of a switch and it goes away... until I idle again.

I'm getting about 5.5mpg per the onboard computer. It's not throwing any codes at all.

At first I suspected it had water in the fuel because all the symptoms showed up about a mile down the road after getting gas (an man was she on 'e') so I dumped some heet in the fuel tank and it didnt do anything for it at all.

I've never seen a fuel filter cause symptoms like this before so I don't suspect it-- anyone have any ideas what would cause this? The truck has been sitting for about 5-6 weeks, but none of these symptoms appeared except excessive vibration for the first 30 miles of driving it. Any ideas would be much appreciated

 

sitting about 5-6 weeks, I assume you drove it enough now to get it good and warmed up to operating temps? If I recall this has some high miles?

I am wondering if you have some injectors sticking or not.

 

yeah I drove it all over last night and today, i warmed it up to op temp yesterday for her maiden voyage. Yeah she's got about 154K and change now

 

I guess my question now is what are the odds this is EGR related or COP related? I have seen many of threads about the coil packs, but haent been able to find too much about the EGR using the search tool

 

I don't think the EGR's are too much of an issue with the gas motors, Could be the COPS but does not seem right to me. I think I would try some carb cleaner followed by some fuel injection cleaner and see what that does to try and smooth it out.

 

a buddy of mine recommended to check out the crank position sensor and/ or the cam position sensor if it has one... how might I diagnose something like this?

 

you know I am wondering if your cat is plugged up. not sure but it would be up front on the vibration dampner, I would think it would have one, easy to take off and check.

 

I dont know what the vibibration dampener is but I can promise it's not the cat, I cut it out and threw it away when I decided it was standing in between me and better fuel economy.

So I believe we have figured it out, I called in my buddy who is a powertrain engineer at GM specializing in performance tuning and design of the LS motors. He bet me beer he's right, so here's his theory:

I have 1 or 2 failing coils. They are not dead, just a really weak spark. When the engine goes under load and is warm is when the symptom shows up. The 'random' misfires at idle are explained by a weak spark at the wrong point in time. By the time the cylinder gets let up it's already on it's downward path and lost some compression. What does light up is enough to register a misfire to the computer. Because it's not a true misfire at idle, the engine tries to correct itself only making the problem worse.

*if a mod motor works anything like a GM motor* the crank position sensor is seeing the non-normal motion in the crank and trying to adjust to that change in rate, plus a non-full strenght spark is causing it to be unbalanced.

When I put my foot into it I get a more harmonic miss, but once it truely starts missing the one lagging cylinder takes the whole bank and throws it off.

If I ease into it I get the idle misses again. One I shut it down, it cools off, it runs 100% perfect until it gets warm again. This just indicates that the coil(s) are working intermittently.

So per the doctors request: get it into a room temp garage, pull all the coils and plugs. Look for the fouled plug(s) and that will be my troublesome coil. If there is no fouled plugs, warm the engine up with plugs back in obviously. Then unhook each coil one by one waiting for the engine to run worse. If it runs worse I pulled off a good coil, if it stays the same I found the bad one.

I hope he's right, just boggles my mind that the way this thing is miss firing it isn't throwing a code.

 

what he is saying makes sense, i just hope that is finally the issue. The vibration dampner is the front pully on the crankshaft. If you notice it is not just a pully.

 

I think the problem is that your truck is haunted and/or possessed and possibly just plain ol' bad luck.

I did a quick search of the threads you've started, and here are a few of the fights you've fought over the past few years...

- My warn hub caught fire...
- HELP! do I need an exorcist or a new radio?
- My steering has gone ape poo!
- Think I broke my truck... darn MI roads
- My truck aint right, please help!
- Super Duty Theft Attempt Please Help!
- 4R100 Slushbox Problem
- We have a severe issue...
- Is my truck going to catch on fire?
- darn truck she's at it again

This didn't do a darn thing to help you out, but I think there might be something to my haunted truck theory.

Hope you get your problems sorted out soon!

 

I had the one or two coils failing issues a couple of years. The truck would run fine cold, then at some random time after warming up, it would start to miss and 35mph was my maximum speed. Then I would shut it down and let it cool for a few minutes and I was good for another short while.

This doesn't quite sound the same because you're getting your power back after a set RPM. As a matter of typical problems, I would start with a vacuum leak check and cleaning the IAC. I'm not so sure about the current design of EGR valves, but the older style was a simple diaphragm which would crack and leak but only when it was active. During heavy throttle and once the engine is warm, the EGR system shouldn't be used much, but on cold start and cruise it may be fairly active.

From what I could discern, ford uses a CPS to watch the velocity of the crank, if the velocity drops sharply when it expects a cylinder to fire and keep things running, it counts it as a miss fire. Watching the missfire counter would be one place to start, also looking at the fuel trims should provide some info on which bank is acting up.

 

Now that you put it like that this has been the truck from hell, why on earth do I like the damn thing so much???!?!?!?!?!?!

Also, this bad luck thing aint just with the truck... since I was about 10 years old everything I own has broken regularly, and oddly enough not because of misuse or abuse... it was nicknamed the anti-midas touch.

I had a brand new chevrolet once, 34 miles on the odo and it was in the shop. Same with my 03 S10 that had god knows how many transmissions put in it. This truck truley has been the best vheicle I ever owned though

 

I like what your buddy at gm was saying but there is one problem if the coil was completly dead and you unplugged it there would be no chage bam there is your coil however they are all firing just weak like he said so you will see a change every time

 

Cause you have your blood, sweat, and tears into fixing it up. Plus, once it is right, you know for sure when and how everything was fixed.

You definitely get an A+ for persistence. Gettin' rid of a problem child is the easy way out

 

If you are getting that many misfires it should store a pending code which most scanners can read. It will show up as Misfire cylinder X (where "X" is the cylinder number). When I replaced plugs awhile back I had two misfiring COPs afterwards. Both cylinders showed misfires under pending codes.

I know Advanced Auto loans auto the Actron line of scanners which most of them can read pending codes.