Bucking and Jerking
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From: PGH,PA
so you're both saying it's more of an issue at low speeds and/or low RPM's? Yes. Seems to be for mine. In my 12 valver, if I was in too high of a gear at a low speed, I would first hear my straight piped exhaust start to rattle and it would take more to get it to kick and buck- alot more. In this 24 valver- with the same identical exhaust, I never hear it do that- it just goes straight into buck you to death. Its exactly like what was said " If you remember first learning to drive a stick shift when you took off in first gear it bucked and kicked until you got it moving" well, its just like that-- only in mine, it isn't when starting off- it happens mostly driving around at secondary road speeds...like 20-40 mph. I guess it would probably do it at highway speeds- if the momentum of the truck didnt prevent it. At least, I never actually felt mine do it at highway speeds but I would bet if I pay more attention to it at highway speeds, I may feel a couple "dead spots" in the throttle range- we'll have to see.
99 cummins...do not feel that i am in any way offended- we both need help! you are totally "on topic".
99 cummins...do not feel that i am in any way offended- we both need help! you are totally "on topic".
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Joined: Oct 2004
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From: Fort St John BC Canada
bucking problems
No what the engine is having a problem with is an arc in the electrical system somewhere. I have seen it on an osocilloscope. Mine has done it since new and cryslurr and cumins aren't able to varifiy it. So we are left to the problem. I adjusted my apps and the diode was marked as to 0.468 vdc I found to to be putting out 0.330 vdc, so I adjusted it to that and it fell back the 0.008 volts but is alot better.It still bucks and that idles like, ummmm excriment. It has better pickup but not till 1500 rpm. It will move better now did manage to pass someone the other day up Taylor hill so that was nice. We shouldn't be the ones that have to figure the engines problems and fix them when cryslurr and cumins are of nooooooo help. Now if I can find an electronics engineer who can help find the problem!!!!! 
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When I am driving around at mostly slower speeds (like around 25mph), I have been getting bucked and jerked to death- as if I were repeatedly applying and releasing the throttle. I have done some research and it seemed that everyone was saying to consider resetting the APPS. I did that...and, made sure to clean all battery terminals well at the same time with no improvement. I tried to key cycle 3 times to pull a code from the odometer and all it said was "pdone". I did the key cycle AFTER I did the APPS reset so, I am unsure if there were any there before I did the reset (When I reset- I left it all unplugged for an hour). When driving around, if I hold the throttle at a specific point, you can actually feel the pedal going "dead" and coming back. This truck has had the vp44 and the LP replaced about a year ago at cummins and I am praying that it is not related (1 yr/100kmi warranty is just past). The APPS is only an assumption- for all that I know, it could be anything. I have no idea if it is sensor or ecm related and I never found a chart on here or anywhere else saying..."ok, if the truck is doing this, its the cam sensor", etc. I cannot afford the $90. and hour diagnosis by Cummins so, I would like to try to figure this out without them. Any ideas? Any and all help will be greatly appreciated!!
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