this happened to me 3 times yesterday coming home. i stopped and bought a drink. when pulling back on the four lane i hammered it and it took off. hit 20#s of boost, 800* egt and and it would hardly go any further. egt was moving up and down 500* fluidly not jerky. let off the throttle, slowed and hit again. same thing only went a little faster and higher on the gauges. did it a few more times and after 1 or 1 1/2 mile it was working just fine. the second time i stopped for fuel and it was doing it again only this time i noticed my ect gauge was only reading 150*. bought my fuel and looked under the hood. saw nothing out of the ordinary. upper radiator hose felt very normal. i could not hold my hand on it very long. took off from there and the same thing. took about a mile and a half to start working normal again. got better as the temp rose. the third was pretty much a repeat of the second. it was like the engine was defueling for some reason. other than those times everything was normal. any thoughts. i could pull no codes with the key. my fuel pressure gauge is broken and i could not tell whether it was fluctuating or not.

Well fuel pressure could be a factor but its unknown because of your broken gauge. MAP sensor could be another that is failed causing some of the issues. Remember a MAP sensor can fail in normal specs and not throw a code. 150*F is rather really cold for these engines your thermostat appears to be stuck open.

i have had an e brake on for about 9 or 10 months and use all the time. i could clean it and see if that helps.if it would quit raining i could install my new fp gauge. got every thing here to do it with.i have had a temp problem for a while. i install a new tstat and it works for a little while then will bounce around 170 to 180. i have been thru 6 tstats in the past 2 1/2 years with the same results. i was going to buy one from the cummings dealer but they wanted $70 for it. i dont know what temp the water was when the gauge said 150, but the upper radiator hose was hot. i could only hold it for 1/4 or1/2 a second. i would have to agree with the temp dropping that quick it sounds like the tstat got stuck open, i am a little tired of buying new tstats. i might just have to buy the cummings and see what happens. $70 just sucks. the one i have now came from NAPA about 3 months ago.

i am trying to install my new fuel pressure gauge. got the gauge in and wired. installed my big line kit and connected my AD to the old filter canister. i ended up with a small leak at both the vp and under the canister. they are both very small and i can make them go away. but i noticed that i have some fuel at the head and intake that must be leaking form the injuector lines. is ther any kind of seal on those connections or should tightning them be sufficient? i dont want to over tighten something and break it. my luck with anything hasnt been good lately.i put another new tstat in my truck before i came down last week end and virtually no differance. never saw 150* but it ran between 165 and 185. up and down the whole trip and this was towing my rv. gcvw has to be around 20k. did see it spike to 191 a few times but then right back into the range mentioned above.before installing the big line kit i had the fuel cannster removed. been that way for 2 or 3 months. i never installed the bolts and did not think any thing of it. but it appears those bolts help hold down the intake. could i have been loosing boost pressure there and could that have been causing the banks to defuel the engine?the other odd thing is after installing the big line kit i drove 16 mile to the rv running 190* all the. plenty of power, boost pushing 31#. i might could see the boost since i reinstalled the filter cannister bolts, but what could i have messed with that would have brought the temp up to normal. i have had the temp problem for a while and grown somewhat used to it. all as worked well until the previous trip when i had low temp and losss of power. the trip to work this am was at 190*. i am confused again:shrug:. we drove home 350 miles and the temp held pretty much just below 190* for the most part. sitll lost temp at any redlight, down to 170 to 175 then right back up when driving again. the mystery continues.