7.3 Studdering and bucking...

[joevillar]

I've had this problem for the last 3 months: Engine cold or hot shudders upon acceleration. Seems like some cylinders are off and when I press the gas they come on. Upon medium acceleration it starts to buck to the point that either I have to punch the pedal or take it off and decelerate.
I've done a cylinder contribution test and a injector test and it passed fine.
Fuel filter has been changed about 6 months ago.
Only mod is Superchip and K&N air filter. (tried standard and all 3 performance programs, all had the same symptom)

1999 f-350 Dually

...any suggestions? Darn truck is giving me a headache from all the bucking!

JR

[rankroddin250]

have you pulled the codes yet?

[joevillar]

No codes yet. I don't have a diag. computer; have to borrow from a friend. Will check for codes asap.

[alabamafrog]

Can't you pull the code with your superchip programmer?
One easy free thing to try without codes is to clean the switch and pot on the throttle pedal with WD40.

[joevillar]

My superchip does not provide (at least I didnt see it) for codes. I just have a basic programming mode.
I will try the throttle pot switch clean. I should have the codes later this week . Thanks for the help so far!
PS You have some serious truck there. Mine is a 1999 also. On how many miles did you have to rebuild and what was the approximate value ($) for all rebuilding and mods?

[alabamafrog]

A good way to test to see if the throttle pedal is causing problems is to see if the same problems happen with cruise control on. Cruise control bypasses the pedal so if the trouble goes away with cruise then it is most likely the pedal and if the problem stays the same with cruise on then it is something else.

A Superchip Micro Tuner (SCMT) I believe the model number is 1701 and/or 1705, should have a diagnostics that allows you to pull codes. Code readers like you can borrow free from places like AutoZone will not work on a 7.3. Most Diesel shops will do a full scan (much better than a code read) and buzz test and contribution test and fuel pressure test, etc for around $75 and they should give you a printout of all the results and the condition of your truck. You may have to check around to find a “good” shop.

I bought my truck with 130,000 miles and it had signs of dusting from the crappy factory air filter. I put the Baldwin open element filter system on it and nursed it to 200,000 miles and decided to rebuild when it failed the compression test I did while replacing the injectors that got crapped out when I got a bad load of fuel. Total cost for everything including fluids was almost $4,000 doing all of the work myself except machining.