03' Big Red

Looks like on 4/12/11 a Mack dealer set up the step 12B downloads and new datafiles for the engine. Its shows the dealer downloaded the new files in their laptop but the dealer didnt send back the confimation file saying they were installed into the truck. Not saying the dealer didnt install them but who knows. It shows u have a fuller 8LL trans and 4.42 rear gears. Truck came with 22.5 wheels but no tire size listed. If your running full size 24.5 tires they might be to tall for your 350 HP. We sold 2 CV's with 400AI's, 8LL trans, 24.5 tall rubber and 4.17 gears. Almost had to buy them back from some very unhappy customers. The AI engine has a very tight window for every thing to work right. Any one thing out of wack/changed and its low power complants. The good thing bout the AI engine is to do HP upgrades you just need to change turbo and injectors and download. Older ETECHs you sometimes have to change the camshaft keyway. In your case you might need to upgrade to a air fanclutch as well.

i did have the local mack dealer check for updates but was not very happy with the service i got from them just trying to get some answers, so i never went back to have the updates downloaded. it does have the 24.5 drive tires. the truck is at a local shop today and they checked fuel pressure, its at 50 psi instead of 80 psi so they are installing a new pump then also running the overhead since that probably wasn't done by the previous owner. they suggested going to a competent dealer and getting any updates then if i need more HP they could do injectors and turbo but i am also considering a Pittsburgh Power box first since it's almost the same price but will give me better drive ability and horsepower increase than injectors and turbo...so they say, it does have a air fanclutch. thanks for you input.

I don't think the AI engine went into any RD's. If your truck is a 2003, it should be an Etech. Have you had your truck back to a good Mack service department to get checked out? That's always the best place to start.

Harrisburg Mack claims it's the AI 350. the truck is at Garden Spot Frame and alignment today, they checked fuel pressure and its about 30 psi low on a cold motor so a new lift pump is on the way, i hear this is a typical problem for a Mack. they will also be adjusting the valves since that most likely was never done by the previous owner.

what is the difference in the Etech and AI ?

all of this talk sounds like my 2003 RD688s with a AI 350, there are many times i wish i didn't buy that truck, i sure hope there is something that can be done.

yes, air and fuel filters are changed on at regular PM.

i have a 2003 RD688S

this truck makes me so mad i could cry, most times it won't pull over 1800rpm and the throttel response is horrible.there is a huge delay when you step on the throttle. i can live with the 350 HP but i just wish i could use it. some times it will pull to 1950 and some times i can feel a stumlbe under accelloration. any ideas on how to get this dog running would be greatly appreciated. if i am correct the motor is a AI 350.

i am also wondering if i can reflash the ECM up to a 400 or 427 with out changing injectors, turbo and such, just in case i need more HP.

the last 6 of the vin are 067246

thanks for any help given !!