jmb4wd Posted March 10, 2016 Share Posted March 10, 2016 Hey guys. Got this new to me 04 RD. Valve cover said it's AI-380. In a hard pull in 5 and 6 gear when motor starts building good boost (30lbs ish) at approximately 1300 rpm the engine flat out hesitates, stumbles and falls back to about 15lbs psi for about 200rpm then picks back up and goes to 30ish psi. It's is very obvious that the engine is derating or something? Any one with any knowledge on this problem? Quote Bryant Construction Inc.06 KW T800 Dump85 GMC General Dump73 Dodge C800 Single AxleMiddle Tennessee ATHS Link to comment Share on other sites More sharing options...
wheeler73 Posted March 10, 2016 Share Posted March 10, 2016 Check your fuel pressure as the gear on the supply pump could be slipping causing a drop in fuel pressure. 1 Quote Link to comment Share on other sites More sharing options...
turckster Posted March 10, 2016 Share Posted March 10, 2016 It sounds like it could be a programming flaw. There were a bunch of engines similar to what you have with the same symptoms. Have your local Mack dealership contact Mack Technical Support to see if there is a program/download for your engine for your issue. I've programmed too many chassis to count that had the exact same symptoms you describe. 1 Quote Link to comment Share on other sites More sharing options...
fjh Posted March 10, 2016 Share Posted March 10, 2016 Does the Check engine light come on when this happens?? If not then and you have a mack 18 sp trans There is a switch on the range cyl ( Or should be)( if not the wires will be there) that can cause the ECU To think the engine is in low it will cut the power in half if the wires re rubbed together or broken they could be causing you greif! Just another place to look Had this happen! 1 Quote Link to comment Share on other sites More sharing options...
jmb4wd Posted March 11, 2016 Author Share Posted March 11, 2016 Thanks guys. Im almost positive its a programming flaw too. Its pretty predicitable and reoccuring. I get no check engine lights so when I get a chance im gonna take it in and get her tuned up Quote Bryant Construction Inc.06 KW T800 Dump85 GMC General Dump73 Dodge C800 Single AxleMiddle Tennessee ATHS Link to comment Share on other sites More sharing options...
Challenger Posted March 11, 2016 Share Posted March 11, 2016 On 3/10/2016 at 8:22 AM, fjh said: Does the Check engine light come on when this happens?? If not then and you have a mack 18 sp trans There is a switch on the range cyl ( Or should be)( if not the wires will be there) that can cause the ECU To think the engine is in low it will cut the power in half if the wires re rubbed together or broken they could be causing you greif! Just another place to look Had this happen! Torque limiter. I had that happen once, years ago. So much time was wasted finding the problem. Quote Link to comment Share on other sites More sharing options...
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