99.5 7.3 missing and 1700rpm bucking - Ford Powerstroke Diesel Forum
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  #1  
Old 10-29-2012, 09:24 AM
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99.5 7.3 missing and 1700rpm bucking

Hey guys. Recently my truck has started acting up. It has 260,000 miles on it. At idle I can feel and hear the truck missing. When it is cold and I put the truck in reverse, it feels like it has a major miss and is going to stall. When I start driving it and I get the truck up to about 40/50 mph, it will start bucking under acceleration around 1500 rpm to about 1900 rpm. It feels like a miss but 10x worse. I took it to get the buzz test and cct done 2 weeks ago and I was told that #4 and #8 were showing low contribution and that it needed injectors for those cylinders. I ordered 2 reman injectors from mylex and replaced those two. The truck had an AD code in #8 but I replaced that with an AE as is whats supposed to be in it from the factory. It had no effect on the problems and has only gotten worse. I have seen many posts about the CPS being blamed for alot of these issues but I have not tried to replace or diagnose the CPS. Anyone else had any of these issues and fixed them? Any ideas?
Thanks,
Nick
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Old 11-04-2012, 07:37 PM
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Some updates. I read that if you disconnect the ICP sensor and notice a difference then that sensor is bad. i disconnected it and the miss at idle stopped. It still had a major miss or bucking at 1500-1800 rpm. I changed the CPS sensor and it made a little difference in the 1500-1800 rpm bucking. It only does it when it when you accelerate. By accelerate I mean barely touching the pedal and it will start bucking within that rpm range. Once you give it more throttle it goes away and acts normal until that rpm range again. When it is missing within that rpm range you can hear what sounds like half the engine not firing because about half of the injector clicking goes away. Sounds like its not firing on the drivers side when its missing. Any ideas at all? Maybe the UVCH?
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Old 11-04-2012, 07:58 PM
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Ok. I have the same exact truck but bigger problems. I know that my number 8 cylinder is practically dead and is smoking like a chimney. I got the truck for cheap so it makes a great work truck. None the less I'm trying not to spend any more money on this truck then I have to, as I have the intention of replacing it. I have had every issue you can think of that these trucks have. I have taken it to all sorts of diesel techs, the diesel specialist, the powerstroke specialist, or ford tech that works out of his garage on the weekend. each one would provide a different yet warranted diagnosis. They all point out the major issues that anyone can digest but the most annoying thing about this truck that none of them can really pin point is this annoying miss that flares up time and time again. Once it begins it becomes progressively worse. To the point where the truck will stall out or shudder and smoke unbelievably. I have posted on this site several times only to be told of how it could be this or that and that its most certainly this.... What I have come to realize its more than likely the oil. This issue may all be oil. Now it may be an indicator of something bigger but to make the truck driveable first try changing the oil. If it runs better then your in the same boat I am and perhaps one of the more brilliant members can point our the real issue you have. Everytime I change the oil the miss goes away for about 3000 miles or 2 1/2 months. I can only offer advise on how to maybe make it more driveable not able to actually properly diagnose the problem. I'm not a mechanic and I'm sure the many members will chime claiming its a sensor but start with the oil. FYI I've replaced every sensor on the top end and the problem persists so shy away from the thousands of cps, icp, ipr, etc suggestions. Start with that.
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Old 11-04-2012, 08:00 PM
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Thanks for the advice and good idea. I will change the oil this week and let you know if that makes a difference. I use motorcraft 15w40. Should i maybe try a different kind of oil?
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Old 11-04-2012, 08:08 PM
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I use shell rotella. I want to try rev x as I believe this is a sign of Stiction but I can more than certainly be wrong. But oil is cheap replacing all the sensors can get real expensive, believe me I've nievley done it. Don't skimp on the oil filter. Also I always open the plug on the hpop when I drain the oil. I do believe some oil gets trapped in there and opening the plug may help release some of this oil but I'm sure someone will chime in shortly to say how dumb this assumption may be but I do it anyway. More than likely I think it's time for all 8 injector replacement when trucks start doing this but it may be something else.
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Old 11-04-2012, 08:14 PM
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Yea i have heard good things about rev x. Ill give that a with my oil change and see if i notice any differences. Thanks for the idea
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Old 11-04-2012, 08:21 PM
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Yeah let me know if it works out for you.
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Old 11-07-2012, 10:53 AM
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Well now i have a new symptom. I have not tried to start my truck in about 2 days and when i tried to start it today, it would run for a few seconds and die. The battery was low on startup and felt like it was not going to start but it finally fired up and ran horribly. It blew a ton of white smoke and felt like it was chugging. It died when i barely hit the gas pedal. I restarted the truck and had the same problem. I disconnected the ICP and tried again but it still died. It was a cold start at about 38 degrees out. Any ideas?
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Old 01-21-2014, 04:50 AM
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UrbanCowboy91, what was the result/fix?

I am having the exact same problem you described in the beginning. Mine starts and runs fine but misses real bad in that 1500 RPM area.

Thanks, Michael
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