Engine/Transmission (1998.5 - 2002) Engine bucking at 1400-1550 RPMS

[grimesja]

Okay guys, I posted a couple of weeks ago without any feedback so I've done some more driving/troubleshooting to provide additional information. The truck bucks, cuts -out at 1400-1550 RPMS especially with overdrive engaged. Dis-engaging overdrive allows me to drive around town at higher RPMS so the truck dooesn't have the issue. It does sound like the truck has a slight miss at low rpms. I still have no codes. I had a transmission tech tell me that it might be transmission related, but again no codes that I can read from the truck or the OBDII, the fuel pressure is good and the truck runs great above 1600 rpm. Anythoughts on electrical or mechanical issues that might casue the symptoms in that power band.

 

[JLandry]

Have you ever replaced the Accelerator Pedal Position Sensor?



If it's not that, it could be the fuel injection pump.



John L.

 

[MChrist]

I'm not sure, either. I wonder if it's related to your poor mileage, though. My 98. 5 5-speed would buck at around 1000 under a load, but that isn't what you are experiencing.

 

[DIESELWRKS]

just to rule it out the bucking is the not the Torq-conv locking and unlocking. what is the rpm gauge doing during this event. is it the when the truck is cold and hot. unhook your edge completely from the truck and see if it still happens. you could try a apps reset. do you know how to do that. that is a 50/50 shot. has there been any maintnance done lately.

 

[grimesja]

I have replaced the APPs a couple of years ago. The problem does not trigger any codes.

The rpm gauge bounces during the evolution. It doesn't matter whether the truck or the ambient temperature is hot or cold.

I'll try the APPS reset, There has been no mechanical maintenace performed lately.

It the problem is more pronounced in overdrive around 45-55. With the OD off I run at higher rpms. If I accelrate heavy, I don't feel the bucking if I accelerate slow, you can feel the bucking start as you pass through the 1400-1550 RPM band.

 

[DIESELWRKS]

hmm. have to think about this one when I get home from work. my issue with my rpm is 2k to 2200 but its like I have lost power during that spot no codes complete rebuilt engine 10k miles ago. I think mine is the injection pump that is 80k miles old and no codes yet. what about removing the edge unhooking it from the sensors and not just turn it off. some problems have been know in the past. I will think about this

 

[grimesja]

do you have any dead pedal? I have gone through about 5 VP-44s (I was getting local rebuilts which were poorly done). I have seen all kind of VP-44 issues but both of our problems is something new. I have had them die wthout any warning. I think might hear a P-pump changeover calling if this is another bad VP-44.



I'll try to remove the edge this evening and give that a shot.

 

[DIESELWRKS]

been pretty happy with the local oregon fuel injection rebuilders. never had a dead peddle, have always had good pressure to it. did apps resets. however never had a single code. I think the pump is just wore out but not setting codes with the tst turned up and smarty up. the bottom end like before is just not there. in due time I'm saving up $ now may do a timbo apps also pending what the volts are reading to the apps.

 

[lkozark]

I have experienced TC hunting which sounds to me what you may be having. This condition has been well documented on this forum. I have cured the problem by cleaning the battery and ground connections. By cleaning I mean clean and sand or burnish them, and apply some silicon grease on the connections. I recently had to do this and it cured TC hunting in OD and at 1400-1500 rpm. Try it, often a simple solution is the correct one. Good Luck

 

[grimesja]

Good Morning Guys, I did the APPS reset last night, including cleaning the ground cables. I drove the truck in this morning without any issues. Thanks guys