99 F-350 7.3L Issues

[workingmark]

Hey all new guy here, not just to this site but to the wonderful world of diesel as well. I have been combing this site for several days now and I can't seem to find anything particular that is causing a diesel engine epiphany. Soooo I am going to post what I am hoping is not one of those common new guy questions. If it is I'm sorry. Anyway, my truck...99 F-350 7.3L Lariat CC LB 4x4. It is lifted and has some sort of six position chip in it. I'm not sure of the brand. I bought this truck knowing that there was some work to do on it but the guy obviously neglected to tell me everything that was wrong with it. First off, I have a constant service engine soon light. Once in a great while it will shut off and then come back on (while driving) I had it checked for codes and there was nothing. Can the transmission cause the light as well? This kinda leads into my next question. The truck accelerates strong but occasionally the transmissions will do this crazy upshift downshift thing several times, when under hard acceleration, before it settles into gear. when it is in a higher gear and I accelerate (such as on the hiway) the engine either starts running rough or the drive train is vibrating. This will happen until I press on the pedal hard enough for it to downshift or I let off of the accelerator. I have been through the drive shaft and tightened all of the bolts, replace the carrier bearing and checked all of the u-joints. I can't figure it out. I am really hoping that it's not the tranny. It's possible that the drive shaft could be out of balance but I don't see how it would cause that much of a shudder that isn't constant. I have other questions but this vibration/rough running is my most pressing right at the moment. Thanks for taking the time to read my book...

Mark

[southend]

Posted in the wrong forum

Sent from my SCH-I500

[RedDye01]

Does it run rough when idling or only under a load

[RedDye01]

Reason i ask us i had an ussue with the under valve cover injector harness that cause a similar problem but it would run rough at idle intermittently also. If it werent for the rough running, id guess your torque converter was having an issue...although a worse case scenario could be you are having two separate issues.

[BigFuel]

Hey and welcome to PSO. Lots of us new guys to the forum but everyone here is pretty friendly and willing to help.

Does the truck act this way in all the different settings of the 6-position chip (careful as one setting might just be a high idle setting and if in gear might pull you into traffic)?

When the truck acts up is it smoking?

Does the truck have gauges (ie EGT, Trans Temp, Boost and the like not part of the standard gauge cluster) and if so what are they reading when the truck acts up?