Well, I'm trying to figure out what the heck is wrong with my truck, is it a driveline thing, coil/electrical thing or both. I had some mods porfessionally installed by a well known mod-motor tuner (intercooler, long tubes, e-fans, tune) and the truck absolutely ran like a bat out of you know where. BUT the check engine light came on, and I started REGULARLY experiencing a vibration that caused the hood to shake, wipers to flap around, etc. intermitantly, usually in the 1750-2100 rpm range, slow speed, 57 mph, 72mph etc. The codes said PO 351-358, coil failure all 8. Took her in to a dealer, they could find no problem. So I cleared code and experimented. Tried running at cruise at the above rpms. Check engine light came on. Vibration ocurred. Cleared the same codes noted. Drove with foot on accelerator. Same thing. You can accelerate through it, but it seems to lack power as yo do then cathes up and runs. Noticed a Leak on a trip. Took it in and it was the pinion seal leak. So I wonder if it is a driveline issue. Cleared codes, drove a bit,acclerated moderately and threw codes without vibration. So maybe a coil/harness or pcm problem. I have an appointment with the tuner May 7, and I should likely take it to the place that did my 4.56 gears, as it could be a gear set-up issue or a drive shaft balance problem. But I have a hum in the rear like I have had before any of the mods noted above. This is weird. ANY HELPFUL THOUGHTS ABOUT WHAT TEH PROBLEM COUL BE??????????

 

Dang. 61 looks and no answers or sugesstions. Tough crowd. Tough crowd. "Pucker up and kiss is Whoville." From the Movie The grinch Who Stole Chiritmas." Just kidding, and yeah, I have kids so i've sen that one a "few" times.

 

Do you have a wideband O2 sensor? I'd love to know what the air fuels are at that RPM range. Possibly running very lean or very rich at that RPM due to a faulty air flow meter or wrongly learned fuel trims..... I really don't understand what would cause that.

 

What does this have to do with Jack Daniels?

 

I don't know but I'm downin a corona right now. .

 

try pulling your MAF sensor and cleaning it, cheap and easy to do and sometimes a dirty or bad one causes symptoms like you've got.. might help, might not, takes all of 5 minutes..
I'll take my JD on the rocks please..

Matt, what color of blue is that? Looks freakin' sweet!!

 

My guess is that it is NOT a driveline problem.

Somthing in the coils and ignition is my guess.

Clean MAF, check all coil & plug connections.. Sounds like it's missing at a certain RPM or somthing.

Run it one time on the dyno and see what the results reveal.

 

No wideband sensor. May have to get one, but A/F was great on the Dyno sheet, so unless something happened.... Cleaning MAF is worth a try I guess. Weird thing is that this does not happen constantly a the RPMs, but it occurs regularly. Thanks.

 

Hmm.......I bet at WOT on the dyno it may not happen and the air fuels are perfect, but I wonder what they are doing when this does happen. I have also seen crankshaft position sensors AND ring gears/flex plates cause this problem. Inproper adatpation of the crankshaft sensor on older ML-320's would cause a random misfire detection at higher RPM's no matter what the load was. Also, there is a C-320 in the shop right now that sets misfires for cylinder 2 and 4 at 1420 rpm if held steady for more than a few seconds and EVERYTHING except the engine has been replaced and I believe they have narrowed it down to the flex plate being faulty. Since the crank sensor reads misfires off of the speed of the flex plate, if the flex plate warps or distorts or vibrates at those RPM's, it can set misfire codes. I wonder if it is possible to put a scope on your CKP and see if the readings go wacky at those RPM's when it happens.


Oh and the color is true blue.......if you catch the sun just right, it really explodes!

 

would the A/F meter in the diag. setting in the dash work?

Just a thought...

 

I don' know. I cleaned the MAF for the heck of it and will test i na bit. I have an appointment withthe tuner may 7, so he can take it out with his computer and see what it does when it vibtates and/or sets the check engine light off. Hopefully that will reveal the problem.