My dad owns a '99 F-250 with the 7.3L PSD. He went on a longer trip this weekend and noticed his truck surging a little bit. He said it happened at random times. He couldn't make it do it and it was almost 10 minutes between the surges. I haven't driven the truck so I can't describe what it feels like or any sounds it makes, but he said it was very subtle and hard to notice. He drove it to work on Monday and said in his 20 or so miles of driving he never felt it surge.

The only mods on this truck are a K&N drop in filter that was cleaned 2 weeks ago and a basic Superchips tuner with the 65-horsepower program installed.

My first recommendation was to reinstall the factory program and see if it helped. I haven't talked to him since so I can't give any updates on how that went. If anyone has any ideas or can tell me something to look for or listen for please let me know because I will be heading home this weekend and will have time to drive it.

Thanks for any help!

 

Putting the pcm back to stock would be a good first step. Though the first thing you should do when you get home is rip out that K&N filter and throw it. They may be ok in other applications, but they are one of the worst things you can do for a PSD. The factory airbox is bad enough sealing on a factory filter, but the K&N its almost impossible. They are known for not getting a complete seal and letting dirt and dust bypass the filter and then dust the engine. To be honest he's better off with just a stock air filter than with the POS K&N he's got. Though he can do an open air intake that will filter better than stock and flow much more. There is a DIY option that is about $40. Anyhow, has he run any fuel conditioner through it recently? Where has he been buying fuel for it lately? Its possible he's gotten a bad batch if he's gone to a smaller filling station that doesn't sell as much diesel. Just follow the big rigs, they usually know where to get the freshest cleanest diesel. If he hasn't run any fuel conditioner through it lately I'd recommend running some Standadyne or Powerservice (my personal choice) through it for a few tanks. Also if he hasn't had his fuel filter changed in the last 15k (normal change interval) you'll wanna get that changed. I do mine every 10k, or about every other oil change. Aside from that you'd have to see if there is any codes present.