Slight Bucking Sensation at Highway Speed

[DonFitzwater]

Any word Alan?

 

[Alan Reagan]

New throttle body installed, new EGR valve and the mechanic said that there was not much soot anywhere. The reflash changed a few operating parameters. I already am seeing about 1. 5 mpg increase on the computer. That's a great change. So far the bucking/miss feeling is gone at 70 mph. I also have felt non on the secondary roads. The morning I took it in, it had started the missing as low as 40 mph. So far it is back to its good running self. The mechanic is thinking that somehow the throttle body was sticking and possible sucking air. Seems to be working fine. He said to keep an eye it and bring it in if it starts again. Thanks for the responses. I did ask about a possible injector problem and he said everything had checked out OK.

I thought about but neither I nor the mechanic found anything loose or chafed. I'm not running any mods so that is not any issue. Stock wiring with no 5th wheel.

 

[Alan Reagan]

You aren't gonna believe this one. After the throttle body was replaced the truck drove fine for about a week and the bucking/missing came back. The truck went in the shop for three weeks and they replaced three injectors that had some carbon. The other three were in excellent condition. The truck continued to buck and shudder and it felt like it was missing. It was very noticeable at temps above 50 degrees.



After opening a Star case, the dealer broke three appointments to take the truck back in. Angry doesn't begin to describe what I was on the last trip in when they told me I needed to get a second opinion on the problem. The truck was down on power, sometimes hesitating when I pressed the accelerator. Mileage was down about three mpg on the highway and worse around town.



I called Ram Customer Care and they reviewed everything and suggested I take it to the dealership in Perry, GA. They were very helpful and opened a case number for me. I had to wait four days for an appointment but it was well worth it. At the dealership, the service manager wrote down everthing I told him. Then he had me talk to the mechanic and he wrote down a bunch of notes. We took it for a ride and he felt the missing/bucking as soon as the truck started to shift gears.



Two hours after I dropped the truck, the service manager called. Here's what you won't believe. It was the fan clutch. The clutch was engaging and disengaging putting significant noise on the engine load signal line to the ECM. The noise was causing the problems with the load signal. When I looked at it on the data download, it would be a flat line that suddenly went crazy with noise spikes. Then it would go back to a flat line like it was supposed to. Althought the fan clutch was not under warranty, the dealership replace it for no cost because I had so many problems at the other dealership. I tipped the mechanic and gave them a great write up on the survey.



The next morning, I picked up my truck with the new fan clutch installed and she runs like a sewing machine. Althought the fan clutch was not under warranty, the dealership replace it for no cost because I had so many problems at the other dealership. I tipped the mechanic and gave them a great write up on the survey.



Mileage on the highway is up to 20. 5 and around town my EVIC is showing 18. 5 this week. When I took it in, it was showing 14. 7 and it is usually pretty accurate.



I will not go to the Warner Robins, GA dealership again if I have any other option.

 

[bigblock_doc]

Check out my post in the engine forum. Been to the dealer 10 times, no codes, replaced the brakelite switch, acc. pedal, and now the EGR valve.

Going on a long ride next week, time will tell.

 

[Alan Reagan]

Check out my post in the engine forum. Been to the dealer 10 times, no codes, replaced the brakelite switch, acc. pedal, and now the EGR valve.

Going on a long ride next week, time will tell.

I was able to duplicate mine in neutral. Rev the engine to 2000 and hold it for several seconds. If no miss, go to 2500 and hold it for a few seconds. If no miss, go to 2800, then 3000 rpms. Mine was temperature sensitive and that's the reason for the various rpms. On warmer days it would do it at the lower rpms. Colder days, I had to go higher. That narrowed it to the fan clutch and the torque converter for the technician.

 

[bigblock_doc]

Thanks Alan.

 

[Gary - K7GLD]

I remember similar electrical spike issues on the 2nd generation trucks as well...



Would never have thought about the fan clutch on a truck like yours...

 

[Alan Reagan]

I remember similar electrical spike issues on the 2nd generation trucks as well...



Would never have thought about the fan clutch on a truck like yours...

Me either. It was very temperature dependant. On cold days, it would take about 15 minutes on the interstate before it would start. On warm days, it would do it right after leaving home.



I saw the data graph downloads and the Engine Load Line would be nice and flat and suddenly would start having signification sawtooth waves that looked like about +/- 3 volts. That's when the engine would seem like it was missing. Once the truck was at operating temperature, it was almost constant. The best way to describe what was happening would be like relay "chatter" where the relay is making/breaking at a high frequency. In this case, it was the fan clutch. When it was doing that, apparently it was inducing EMI back into to Load Line.



I just returned from a 1600 mile round trip. Overall mileage for the trip (calculated) was 20. 2 mpg. The trip was to Alexandria, VA so there was a fair amount of stop and go once I got up there. On the return trip, the EVIC made it over 21 mpg. This has made a heck of difference in the truck. Pulls good. Mileage is up. I'm alot happier.

 

[Alan Reagan]

I remember similar electrical spike issues on the 2nd generation trucks as well...



Would never have thought about the fan clutch on a truck like yours...

Me either. It was very temperature dependant. On cold days, it would take about 15 minutes on the interstate before it would start. On warm days, it would do it right after leaving home.



I saw the data graph downloads and the Engine Load Line would be nice and flat and suddenly would start having signification sawtooth waves that looked like about +/- 3 volts. That's when the engine would seem like it was missing. Once the truck was at operating temperature, it was almost constant. The best way to describe what was happening would be like relay "chatter" where the relay is making/breaking at a high frequency. In this case, it was the fan clutch. When it was doing that, apparently it was inducing EMI back into to Load Line.



I just returned from a 1600 mile round trip. Overall mileage for the trip (calculated) was 20. 2 mpg. The trip was to Alexandria, VA so there was a fair amount of stop and go once I got up there. On the return trip, the EVIC made it over 21 mpg. This has made a heck of difference in the truck. Pulls good. Mileage is up. I'm alot happier.

 

[bigblock_doc]

They replaced the EGR. Gone three thousand without a problem. Either they cleaned the butterfly while it was apart or that was it.
Keeping my fingers, toes, arms, legs crossed. And anything else I can cross.