Help!! Engine running rough!!

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Mar 14, 2013 | 10:36 AM

Greyliner

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Joined: Aug 2012

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Help!! Engine running rough!!

Hi Guys, my truck is running really bad. 1997 Ford F-250 213,000 miles. Its wierd it will run bad and 15 to 20 minutes later it will run rough still just not as bad. When it runs the roughest the rpms will fluctuate 300 rpm and when it runs its best it will have a surge of 100 rpm rise and then settle down and for a second or two and then do it again. I tested fuel pressure using a tire gauge at it reads 38 psi but i dont know how accurate that is? I replaced Valve cover gaskets and UVCH on both banks. Clean oil, always changed every 4000 miles. Clean fuel always using Stanydyne. I just recieved my AutoEnginuity and plugged it in and Performed all the tests and they all passed. ICP is 564 at idle and ICP duty cyle is 18.75 but whats wierd is the ICP duty cyle varies, i will check after like 3 minutes and the the duty cycle will be at like 14.45 and then 3 minutes later it will be at 12.30 i dont know if that is right or not. But this is all that sticks out to me using AE for only a coulple of hours. Manifold pressure matches my back pressure psi. I really dont know what the values are supposed to be on all the sensors i am looking at.... Please help with troubleshooting this problem. Im pulling my hair out!!

Mar 14, 2013 | 11:16 AM

mjunk1

Fleet Mechanic

Joined: May 2005

Posts: 1,739

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From: Vale, NC

This thread from Mike gives all the info on the sensors. It should help you cross-reference the readings you are getting.
https://www.ford-trucks.com/forums/1...nsor-info.html

I suppose the easy questions about replacing a CPS and unplugging the EBPV might be worth answering.

Mar 14, 2013 | 02:02 PM

Greyliner

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yes i have replaced the Camshaft pos sensor and i have unpluged the ebpv and no changes were made. Thank you for the reply i will go over the list of sensors you gave me and compare to mine on AE tonight. Thank you!!!

Mar 14, 2013 | 02:14 PM

fordpride

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Joined: Dec 2009

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From: Livoina,La

Is the ICP rising and dropping with the duty cycle ?

Mar 14, 2013 | 02:21 PM

Greyliner

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Thanks for the reply, here are the exact psi's and duty percentages that i recorded at numerous times through the troubleshooting last night. All were taken at idle. Thank you!

545.28 psi 16.01 Duty cycle
564.52 psi 18.75 Duty cycle
576.96 psi 19.14 Duty Cycle
579.57 psi 14.45 Duty cycle

Mar 14, 2013 | 03:15 PM

ReBilld

Hotshot

Joined: Jan 2012

Posts: 11,132

Likes: 3

From: Southern West Virginia

Unbolt the IDM and take it out and shake it. See if it sounds like there is water in it.

Mar 14, 2013 | 03:38 PM

Hussler

Postmaster

Joined: Sep 2007

Posts: 4,195

Likes: 6

From: Medford Oregon

Duty cycle changes with engine oil temp. On first start of the morning mine is up around 19% but drops to around 12% once the engine heats up. Don't know, maybe HPOP can pump warm oil more efficiently than cold oil.

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Mar 15, 2013 | 09:31 AM

Greyliner

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Ok guys, i removed the IDM last night and it was dry as a bone I shook it and turned it in every direction. Inspected pins and wiring harness, everything looks good. I then put everything back together. Then replaced the CPS (again). I then hooked up AE and was still running poorly. As the truck was still running after warming up i disconnected the EVPV and still ran the same. After the truck warmed up to normal operating temp i thought i would watch certain sensors and see what happens as i slowly rev up the truck to max rpm. As i looked at the Manifold Gauge psi on AE i noticed that when (parked) and i reved up to max rpm the psi always read 0 and so i verified by watching my boost gauge on my pillar mount and it also read 0. So i then Went for a drive and recorded about 5 minutes of driving at different speeds and have it on an excell spread sheet. Maybe you guys can help me decifer the info. Also how do i post it on this thread for you guys to view? Thank you guys for all your help!!