I was watching rpm on scanner and it was fluctuating from around 920 to 990. Same results, went to 1k rpm, idle ran smooth for about 20 sec then started missing and cutting out. The ect was 60 deg and the Iat was reading 58.7 deg on cold startup. I recalibrated my timbo apps and started my truck. 030vac. Any ideas? What will make a cummins idle high? ecm? I have auto enginuity on my laptop to scan with. I checked for ac voltage and got a high of. Batteries are 6 months old and test good. All exh temps from exh man are within 40 deg f of each other. Only code its giving is p0234 and I found waste gate stuck. Fuel psi is 19 at idle with a air dog 100 lift pump. Truck runs out great as long as its accelerating but when you let off throttle you can hear it miss. when put in gear, it idles 900 rpm and smoothes out under load of trans while in gear. Idle stays at 1k and misses unless put in gear. Happened out of the blue while wife was driving. I have a 99 24v, 4x4 auto 134k miles that started idling at 1000 rpm's and has a miss to it. Got to work 25 miles later and the engine idle was up.Newbie here so please be gentle. It's not cold enough to warrant it, but last night I plugged the truck block heater into the timer, so when I fired it up this morning the engine idled at 850ish (did not think to look at ECT on OBDLink). The "high trans temp" light isn't on, but does the engine high idle to circulate fluid when it believes the transmission is hot but not "so hot I need to light the dummy light"? The ECT is used by ECM which then feeds a signal to the dashboard gauge, correct? Or are they a parallel circuit with the gauge and the ECM reading the same sensor but not affecting one another? I ask because the gauge reads the way it always does, but if it's a parallel path then the wire feeding the ECM could have an issue and make it up the idle, right? The fact it all started with the transmission service is the odd thing to me. I reconnected that while the engine was running, and to absolutely no surprise at all nothing happened with the idle.Ī bad ECT sensor reading low will cause high idle While crawling under the truck, I noticed my red CAD vacuum line worked its way out of the elbow (again). Could I have done something wrong in the valve body work to cause this? Pressure/temperature sensor connection wasn't removed, and I did push on it just to make sure it was still connected before putting it all back together. The 8-way electrical connector went back together exactly as one would expect, smooth with a nice click. This issue also came up IMMEDIATELY after transmission service. Is it possible that I have a lot of oil blowby though the turbo causing such a problem? I have strong doubts that's the problem because the truck drives the same as always and the idle is super stable. As a side note, the air filter is newish and still very clean. Will read the OBDLink with engine off before unhooking batteries to make sure it reads 0 PSIG, ~14 PSIA, or equivalent in metric. Hoping a little battery-free reset will do some good.Ī fellow here also recommended I check to make sure the MAP sensor is reading correctly, that "if he recalled correctly" the MAP sensor reading can trump the ECM's desire to idle at 850ish. Meant to unhook batteries when I got to work but forgot. No tuner of any kind, though I do desire to purchase one!
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