first off, i'm new to this side of the forum, but been around the van and diesel sides of the forum for awhile. howdy guys

i'm working on a customer's 01 e350, and it has a good bit of a shudder when in overdrive. because the shudder goes away when not in overdrive, my initial belief was a transmission problem, but i googled the problem and found it to be very common, sometimes a result of an engine misfire, other times a TC problem.
on to the details of the problem... whenever the van is in overdrive and the driver is stepping on the gas any at all, there is a quite noticeable shudder. it goes away when fully letting off the gas pedal or when shifting out of overdrive, and returns as soon as you're back on the gas while in overdrive. my test drive ranged from 0 - 80MPH and was totally smooth, as long as i kept it out of overdrive, but rough anytime it was in OD
this appears to me to be a problem in the transmission, as no combination of gas, gears, and braking (to add load to the engine while gassing) would produce even the slightest bit of roughness. however, reading up on the problem seems to indicate that bad coils have been known to cause a similar shudder when under load.
my logic says a tranny/TC problem, but what i've read points to ignition.

the CEL is off, and the data link connector has a problem in which it won't power my code reader, leaving me unable to more precisely study its problem that way. is there a somewhat affordable (500 or less) code scanner thats self-powered to solve this problem, or should i try to restore power to the DLC? or does this problem indicate a greater problem in the computer system?

what do you guys think?

 

Josh I believe the DLC has to have power even if your scanner is self powered---I say that because on more than one occasion a blow fuse has caused any connected scanner to not function properly. My '00 EVTM shows a 20 amp fuse in slot #23 of the inside fuse block---this fuse is shared by the cigar lighter port.

I bought the Actron CP9580 for just at $150 and it has impressive capabilities. Amazon has them free shipping or Advance Auto parts et al can order them too. Actron has a great selection of readers and scanners depending on your budget. I'm sure there are other brands just as good and useful but this is the only one I've owned and it works well for me.

FWIW I've experienced this same set of conditions as you describe and it was tracked back to bad or failing Granatelli COP's. Once the known bad ones were replaced that shudder disappeared.

HTH

 

JWA, thats good to know. this is the second vehicle i've worked on that wouldn't power my reader, and i had the idea (without really knowing) that a self-powered unit might solve it.
i have a good code scanner i bought off the snap on truck for about 150, it includes the ability to read current sensor readings and more, so not a basic cheapo. i was only looking into another if it would improve my ability to read those with ports that lost their power.
for this van, i'll get in touch with the owner and try replacing the COPs and plugs

 

Josh sounds like you've got a good enough scanner already. I bought mine with the expressed idea being able to cancel codes in order to quickly check the work I'd do.

Hope you work this out easily----doesn't sound too complicated so far.

 

When COPs start to fail they cant fire the mix when the EGR is activated causing a bucking until you let off on the gas= EGR shuts off, wide open=EGR shuts off, turning off OD=EGR shut off, PCMs dont see this as a hard miss, and it could be any of the COPs

 

you would think someone would reprogram the computer to help us diagnose these issues, as they are so common... any software guys looking for a project