Im just in a lot of pain today from my surgery, but i did tell them what it was. I wasnt guessing, i know for 100% sure that's what it is.

 

BfB- I just have a rough idle while in park or while in gear, otherwise truck runs fine.

Struck- We just got back from vacation Saturday, so Ill get that body out asap.......the hobby shop didnt have a the F350 body I wanted.

jefflaws- I checked and everything seems to be connected at the brake res. and everywhere else also, so I have no idea how that ugly **** got there!!! Im still looking EVERYWHERE though! LOL!

 

Just to ease everyone elses doubts, would u please compare it to the part of the sensor that sticks out of the master cyl. reservior and make sure the connector fits it and report back?

Also, for your rough idle, i hope it isnt what it usually is in our shop when a newly installed head has a roughness only at low rpm.

 

So explain for us please!

 

Well, just to make sure its not something stupid, make sure it only has 6, instead of 7 quarts of oil in it. 7 very much can cause a rough idle.

But what we find over and over, is that out techs that do engine work on 4.6 and 5.4s do NOT follow the revised correct way of installing the timing chains. I have photocopied instuctions that i recieved from the hotline, and they still want to do it their own way,(like painting marks on the chain and gears before they disassemble) and that has proven to cause just enough compression difference between the 2 banks to make a rough idle that isnt evident above 1000-1200 rpms. It can be real hard to diagnose this sometimes, the best way, is to make a graph with WDS and you will start seeing a pattern that exists only on the bank of cylinders that was worked on.

 

jefflaws-Ill snap a pic of it later. Yea, please explain the head thingy! Looking at the scanner, my O2 sensors are going nuts! Put the scanner on my friends Lightning and his O2 graph has perfect up and down lines where mine are all jagged and seem to be breaking apart! Any ideas?

 

Man, its gonna be hard to diagnose without WDS.
A scanner or even NGS would be impossible to run the type of crankspeed/time tests like the powerbalance option in WDS.
The O2 readings will tell u a little about it, not much. However even a very erratic switching of over and under .5V is a good sign that there isnt a vacuum leak or fuel metering problem causing it. I hate to say it, but youre gonna have to put the diagnosis back in the hands of a dealership. (you wanna make a trip up to NC? lol).

Do one thing for me, Drop it into drive with your foot on the brake. You feel the roughness? ok, now tell me at what rpm it totally goes away and is powerbraking smoothly.

 

Skank Dog

Do you have an aftermarket filter in your truck?

I had the same problem with my idle in park or in gear. Found out that the K&N filter oil gummed up the MAF sensor. Put on a spare 90mm MAF that I have and the idle problem went away.

Just a thought

Check to see that the O2 sensor behind the passenger side head is plugged in all the way. Easy to try, you have nothing to lose

But I'm sure jefflaws, who just knows everything about everything, will shoot these ideas down too

Send that r/c body over and I'll send you back a nice flame paint job with whatever color metalic base color you want. I was thinking a deep metalic red with two layers of orange, yellow, and white flames that overlap each other. What do you think?

Jason

 

jefflaws- With the truck in gear and my foot on the brake, the roughness goes away as soon I start pressing the accelerator. Ive run the rpms up to 1000 and 1500 and it never misses a beat, really smooth. While in park though, when I run the rpms to 1000 or 1500 it will not hold a steady idle for !@#$!! The rpms are bouncing all over the place, it starts smoothing out about 2500!

Struck- That paint job is exactly what I had in mind also!! Do it that way. As soon as the hobby shop gets my body in, Ill ship it to ya!!

 

Thats what i expected you to say, it really does sound like a compression difference between banks.

Anything left unplugged would have turned on the check engine light by now, a lean miss/Vacuum leak would turn on the light after a short while and your O2s would not be switching like you said they are. A messed up MAF (like struck by had) would most likely be evident by a hesitation/stumble if you "goose" it real hard from idle.

I cant really think of anything else it could be, think about it like this - a mis-timed cam will make it kinda like a "race" cam, loping at idle, but then at a certain rpm the compression changes enough to make it smooth out and run good.

Its one of those things where "If it was here in front of me I could fix it" but being halfway across the country, i can only tell you what i know from experience.

I would take it back in and let them fix it, maybe even slightly hint around about checking the powerbalance on WDS and seeing if its isolated to the one bank they worked on. They are probably going to want to rule out a lot of other stuff first, because no one likes pulling the vavle cover and timing cover back off to check the cam timing. (Said from experience).

Good luck

 

jefflaws- Thanks very much for the help, your the only person so far thats been able to shed any light on whats going on. What gets me though is at initial startup (after the repair) the engine idled very smooth and ran smooth for two days then this rough idle started. Wonder if it has a blown head gasket? Would that cause a rough idle as well? Seems like the idle is getting worse. Oh well, maybe whatever it is will cease to function sooner or later.

Rodney

 

well, if the chain was off when they assembled it, it would have been like that to start with. There is a plastic cassette in there the chain runs on that could break, causing a shift in the cam timing. Head gasket could be possible, but not as probable.

Since i cant be there to put my hands on it, i cant say anything for sure, heck, it could be a contaminated O2 from coolant running down the exhaust when it was diasassembled. But one thing is for sure, they need to fix it, without you having to try to diagnose it for them. Im sure they have someone there that can figure it out for you.