Itinerant Air-Cooled

hello, this is kris. My bus is pausing and jerking often when i am driving it. Could this be an AFM issue or timing issue? I am just learning, but would appreciate any feedback and would like to address this myself. Thanks folks, kris

khargis wrote:hello, this is kris. My bus is pausing and jerking often when i am driving it. Could this be an AFM issue or timing issue? I am just learning, but would appreciate any feedback and would like to address this myself. Thanks folks, kris

Jerking while driving is unlikely to be due to timing. I would start your search elsewhere.

More information is needed in order to give you the best advice. Tell us when you notice the jerking and pausing. Just on acceleration, at cruise, or decelerating? Is it more of a bogging sensation, then taking off, or does it just cut out for a moment, then back to normal? Or is it herky jerky the whole time? Does it happen when the engine is warm, cold, or both? What helps and what makes it worse? Does the engine run okay when you are checking it in the driveway, or does it manifest these symptoms even when you are in neutral and you manipulate the throttle sitting still?

From my recent troubles with jerking (see viewtopic.php?f=42&t=11172), I have learned that you need to check every connection related to the double relay (multi-wire connector on left firewall), the connector on the AFM, and the connector to the Temp Sensor 2. You should also check the points, and the function of the Temp Sensor 2 (easiest to just replace it maybe). There are also fuel delivery issues that could cause symptoms like this. Tell us when you last changed the fuel filter or if the fuel tank might be in questionable condition.

Let us know what you find.

Tim

satchmo wrote:

khargis wrote:hello, this is kris. My bus is pausing and jerking often when i am driving it. Could this be an AFM issue or timing issue? I am just learning, but would appreciate any feedback and would like to address this myself. Thanks folks, kris

Jerking while driving is unlikely to be due to timing. I would start your search elsewhere.

More information is needed in order to give you the best advice. Tell us when you notice the jerking and pausing. Just on acceleration, at cruise, or decelerating? Is it more of a bogging sensation, then taking off, or does it just cut out for a moment, then back to normal? Or is it herky jerky the whole time? Does it happen when the engine is warm, cold, or both? What helps and what makes it worse? Does the engine run okay when you are checking it in the driveway, or does it manifest these symptoms even when you are in neutral and you manipulate the throttle sitting still?

From my recent troubles with jerking (see viewtopic.php?f=42&t=11172), I have learned that you need to check every connection related to the double relay (multi-wire connector on left firewall), the connector on the AFM, and the connector to the Temp Sensor 2. You should also check the points, and the function of the Temp Sensor 2 (easiest to just replace it maybe). There are also fuel delivery issues that could cause symptoms like this. Tell us when you last changed the fuel filter or if the fuel tank might be in questionable condition.

Let us know what you find.

Tim

See? I TOLD you there were sharp minds around here.
ColinAtThePoolSnoozing . . . NOT

Just to add one more bit to Tim's solid advice:

Look at the electrical connections in the ignition system as well. The wire from the FI to the double relay (covered in the double relay), the wire providing 12V to the coil, etc...

I had this issue twice. Once, it was poor contact with the 12V wire coming into the coil. Cleaning up and tightening that connection solved the issue. The second time, the wire from the the coil that goes to the fuse holder/FI/rear brakes had been damaged. The damaged part of the wire was not easily visible, and it occasionally would contact the engine tin and cause the bucking/jerking.

Good luck to you!

thanks y'all, i will be taking a look this weekend and have a better idea. I do know that the bucking seems to happen when the bus is cold and she is cruising at a steady clip, accelerating seems to make the buck/pause stop for the moment, then the bus will drive fine. i appreciate the feedback. kris (also, the engine runs fine in the driveway, it just happens while i am driving) and it has been a while since i changed the fuel filter and the tank seems to be in fine condition..

khargis wrote:thanks y'all, i will be taking a look this weekend and have a better idea. I do know that the bucking seems to happen when the bus is cold and she is cruising at a steady clip, accelerating seems to make the buck/pause stop for the moment, then the bus will drive fine. i appreciate the feedback. kris (also, the engine runs fine in the driveway, it just happens while i am driving) and it has been a while since i changed the fuel filter and the tank seems to be in fine condition..

The above highlights suggest that it is a mixture issue. Does the symptom go away when is warm or does it get worse when it is warm?
Colin

hey there colin. it seems to go away for the most part when the bus is warm. does this mean the AFM needs to be tinkered with?

khargis wrote:hey there colin. it seems to go away for the most part when the bus is warm. does this mean the AFM needs to be tinkered with?

I think more likely the Temp Sensor II. It is supposed to send a signal to the computer that the engine is cold and needs a richer mixture to go along with the extra air that the AAR is providing. If it isn't working right, there isn't enough enrichment during warm-up.

Tim

satchmo wrote:

khargis wrote:hey there colin. it seems to go away for the most part when the bus is warm. does this mean the AFM needs to be tinkered with?

I think more likely the Temp Sensor II. It is supposed to send a signal to the computer that the engine is cold and needs a richer mixture to go along with the extra air that the AAR is providing. If it isn't working right, there isn't enough enrichment during warm-up.

Tim

There was a fix, a steel washer that you are supposed to put under the temp sensor II to slow its warm up. Do you have that washer under your temp sensor II?
Colin

thanks again, i will check in the morning.

kris

alright folks. I located the temp sensor II. The wire and connection was all mucked up with grease/oil, so i cleaned it off and found the connector to the wire was pretty much shot. so i disconnected from the tpII and snipped wire from connector, cleaned tpII terminal and surroundings, attached a new connector to tpII wire and voila. I will monitor while driving later today and get back to the people. Thanks a bunch for all your help. I realize that this (possible fix) was not rocket science, but every little bit helps! kris

khargis wrote:alright folks. I located the temp sensor II. The wire and connection was all mucked up with grease/oil, so i cleaned it off and found the connector to the wire was pretty much shot. so i disconnected from the tpII and snipped wire from connector, cleaned tpII terminal and surroundings, attached a new connector to tpII wire and voila. I will monitor while driving later today and get back to the people. Thanks a bunch for all your help. I realize that this (possible fix) was not rocket science, but every little bit helps! kris

Practice, m'boy, practice.
Colin

yes pa...

hello again, the bucking and jerking is back and badder than ever! the short of it, recently tuned her up, valves good, new distributor and bosch points - check, dwell between 40 and 50, new temp sensor II. I was going thru Eugene, south 2 hrs from portland and the bucking began. I checked the fuel filter and it had some rust chunks, replaced it and the bus ran solid for about 45 min and the bucking slowly reinstated itself, by the time i got to Redding, CA (about 6 hrs south) it was pretty out of control. Tomorrow i will check the filter again and blow out, reinstall, etc. So I guess my tank is in bad shape? I will double check all connections to the dbl relay, coil, etc. If I do have more rust chunks in my fuel filter tomorrow, do I just keep cleaning the filter until i can pull the tank? I am headed to san francisco tomorrow for a months work and want the bucking to stop. I feel like i have been rode hard and put away wet! Thanks people, kris (any thoughts?)

hello again, the bucking and jerking is back and badder than ever! the short of it, recently tuned her up, valves good, new distributor and bosch points - check, dwell between 40 and 50, new temp sensor II. I was going thru Eugene, south 2 hrs from portland and the bucking began. I checked the fuel filter and it had some rust chunks, replaced it and the bus ran solid for about 45 min and the bucking slowly reinstated itself, by the time i got to Redding, CA (about 6 hrs south) it was pretty out of control. Tomorrow i will check the filter again and blow out, reinstall, etc. So I guess my tank is in bad shape? I will double check all connections to the dbl relay, coil, etc. If I do have more rust chunks in my fuel filter tomorrow, do I just keep cleaning the filter until i can pull the tank? I am headed to san francisco tomorrow for a months work and want the bucking to stop. I feel like i have been rode hard and put away wet! Thanks people, kris (any thoughts?)