No Throttle Response 10- 15 Times Per Day

[fuelsaver]

Hello everyone

i am new here and looking for some help and to find out if this is a comon problem on these trucks.

i have a 2003 rb688s truck with an e7 engine

While driving the truck down the highway or city streets the throttle will soose response and go to idle for about ten seconds or so.Or if your sitting at the lights ready to make that left hand turn the throttle will not respond (just goes to idle.....engine never shuts off and no engine light) then it will come back and a way we go.

We have scanned the engine for codes.

found low coolant sensor code and #5 and #3 unit pumps.

we replace the coolant sensor

replaced both unit pumps

replace the engine position sensor just in case.

replace the throttle pedel assembly and check wiring up under the dash for cuts or grounding out.

check wiring from the ecu to the cab.

set top end of the engine.

checked the wiring from the coolant level sensor to the ecu...Note ecu is located on the left side of the engine..

no rotted wires or pins...very clean at both ends.

The only time now we see the engine light on is first thing in the morning while the ecu is testing it.

i am thinking it maybe a bad ground or power feed to the cab..but the gauges and lights never flicker.

we have replace fuel filters and done complete service in the past week.

thought it may have been the jake brake or cruise switches so we dissconnected the wires from the switches and drove the truck around with still the same problems

onething to note when the truck was new at around 50000 k/m the first engine blew a rod out the side of the block......then around 90000k/m the second engine blew up......both replaced under warranty....but now 7 years latter and 450000k/m more we have this little problem.

any help or suggestions would be great

thanks in advanced

have a great day.

[cgallamore]

Hello everyone

i am new here and looking for some help and to find out if this is a comon problem on these trucks.

i have a 2003 rb688s truck with an e7 engine

While driving the truck down the highway or city streets the throttle will soose response and go to idle for about ten seconds or so.Or if your sitting at the lights ready to make that left hand turn the throttle will not respond (just goes to idle.....engine never shuts off and no engine light) then it will come back and a way we go.

We have scanned the engine for codes.

found low coolant sensor code and #5 and #3 unit pumps.

we replace the coolant sensor

replaced both unit pumps

replace the engine position sensor just in case.

replace the throttle pedel assembly and check wiring up under the dash for cuts or grounding out.

check wiring from the ecu to the cab.

set top end of the engine.

checked the wiring from the coolant level sensor to the ecu...Note ecu is located on the left side of the engine..

no rotted wires or pins...very clean at both ends.

The only time now we see the engine light on is first thing in the morning while the ecu is testing it.

i am thinking it maybe a bad ground or power feed to the cab..but the gauges and lights never flicker.

we have replace fuel filters and done complete service in the past week.

thought it may have been the jake brake or cruise switches so we dissconnected the wires from the switches and drove the truck around with still the same problems

onething to note when the truck was new at around 50000 k/m the first engine blew a rod out the side of the block......then around 90000k/m the second engine blew up......both replaced under warranty....but now 7 years latter and 450000k/m more we have this little problem.

any help or suggestions would be great

thanks in advanced

have a great day.

have had this problem on several trucks like yours, every time it was throttle pedel servo, if driver used air to blow out inside of cab, it would happen again very quick, after a while found we could clean servo with brake cleaner, fixes it 9 out of 10 times, took a few of them apart found one grain of sand would cause it to do that. now i only vac inside of cab, i never use air to blow floor clean, hope this helped?

[Mackpro]

Hello everyone

i am new here and looking for some help and to find out if this is a comon problem on these trucks.

i have a 2003 rb688s truck with an e7 engine

While driving the truck down the highway or city streets the throttle will soose response and go to idle for about ten seconds or so.Or if your sitting at the lights ready to make that left hand turn the throttle will not respond (just goes to idle.....engine never shuts off and no engine light) then it will come back and a way we go.

We have scanned the engine for codes.

found low coolant sensor code and #5 and #3 unit pumps.

we replace the coolant sensor

replaced both unit pumps

replace the engine position sensor just in case.

replace the throttle pedel assembly and check wiring up under the dash for cuts or grounding out.

check wiring from the ecu to the cab.

set top end of the engine.

checked the wiring from the coolant level sensor to the ecu...Note ecu is located on the left side of the engine..

no rotted wires or pins...very clean at both ends.

The only time now we see the engine light on is first thing in the morning while the ecu is testing it.

i am thinking it maybe a bad ground or power feed to the cab..but the gauges and lights never flicker.

we have replace fuel filters and done complete service in the past week.

thought it may have been the jake brake or cruise switches so we dissconnected the wires from the switches and drove the truck around with still the same problems

onething to note when the truck was new at around 50000 k/m the first engine blew a rod out the side of the block......then around 90000k/m the second engine blew up......both replaced under warranty....but now 7 years latter and 450000k/m more we have this little problem.

any help or suggestions would be great

thanks in advanced

have a great day.

When this happens does to engine stay at 650 rpm's or does it go to 900 rpm's. If the throttle pedal is bad it usually gives a code or if its the J1939 link the engine idle is 900 and the throttle wont work. I would try a new pedal anyway even without codes it could be bad. Heres parts of an email I got from the Mack enginners years ago even though your is not a CV or CT it could still have this jumper.. Had an issue with throttle cut out on a CV chassis. Found the problem to be poor connection on jumper at the body builder connection. Spoke with Dave Troupe in Allentown and verified the purpose of the Jumper to be for installation of Remote throttle control by Body builder. The jumper wire is to keep the throttle in operation until the body builder is done. If there is no remote throttle control installed then the jumper stays there. This is on 2004 and up Mack CV and CT. If there are complaints of throttle pedal cutout and codes check jumper wire at body builder harness behind right side lower kick panel by the VECU. This jumper wire tends to have a bad connection and will cause throttle codes. If bad cut the two wire ends and solder them together and cover with heat shrink. Do NOT remove tags from wire.