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Hiccupish idle

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Got one giving me fits here. 2012 F-550 with a crane/service body. 77k on the clock not sure of the hours (i am away from the truck at the moment). As long as the truck is at idle it will do like a hiccup thing (kinda like a PCM reset when it's 5 volt ref shorts out for a split second). The engine will rev for second then idle fine then lope then idle fine then rev then idle and on and on. 

 

Not a code to be found in any module. Truck had factory fuel filters on it  :surprise: so I changed them. I took a fuel sample and it was good. I popped out the VCV and checked for metal (had the intake off putting a turbo coolant fitting on) it was all good. Checked fuel trims with nothing exciting to report. Looked at VCV and PCV pids and the VCV would spike when the odd idle event occurs. Contacted hotline and they said a frigged up FRP sensor could cause that. I unplugged the sensor and it idled fine. I replaced the sensor and it still acts up.

 

If the truck is raised off idle even a 100 RPM it wont act up. I also have trouble getting it to do it in gear at idle. Put it in park and everything is jabberwonky just like the power balance screen. I mean the traces are all over the place. I'll try and post some screen shots later. I am at a loss at the moment.

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Bit more info. 2223 hours and 481 idle hours with 77098 miles = 34.68 MPH and 160.28 MPIH. The customer needed the truck and when I backed it out a few minutes ago it acted up while idling backwards in reverse out of my bay. Here is a screen shot with minimal pids, the spikes happen when the truck surges.

 

john deere surge.jpg

 

I checked the turbo for any issues and its straight. VGT pid doesnt show any issues either.

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If I take command of the VCV or PCV it wont act up. I looked at a shit load of pids and the only ones I saw that changed in unison were the four I narrowed it down to in the posted screen shot.

 

I save screen shots by first hitting the print screen button on the keyboard, then opening up the paint program, then pasting it in the paint screen. You must use the save as button and it will default to PNG. You need to hit the down arrow in the "save as type" bar and this will open up and give many options. I use the JPEG option then name the picture and put in my pictures section (not documents, or downloads or ect.) this allows me to mark up or alter the image later.

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Odd.

 

Have you taken a peek at the pto contols? Alot of the body builders are using a electronic speed control module to control their equpitment. Its typically mounted righ under the steering wheel near the DLC. On our crane trucks  I have had this module cause some weird issues even when the pto/crane  isnt turned on

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Off subject but how do you save a screen shot? I have printed screen shots but not been able to save.

 

CTRL + ALT + PRINT SCREEN

 

When those are pressed at the same time (and print screen needs the 'function' key pressed too, if it's a Toughbook) it saves a 'copy' of the screen capture to the clipboard. Hop to MS Paint - or your imaging program of choice - and 'paste'. The screen capture will display and you can save the image as you please.

 

Edit: Sorry to duplicate Brad's instructions

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  • 1 month later...

You know how they say a truck will have to get worse before it can get better? Well this one just came back In on the hook, motor raising hell and a gigantic hole in the oil pan.

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Number 1 main bearings spun and then seized. Crankshaft continued to turn at all costs. The rear of the crank separated itself from the front just behind the number 1 and 5 rod journal. The bearings then got pounded into submission and it dumped a shit tonne of oil out of the front crank seal. The resulting freedom of movement on the front pistons allowed the pistons and valves to get up close and personal. Long block approved no questions asked......I sent photos.

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