Motor races while coasting on '92 Dakota
From : john corliss
Q: engine is a 2.5 liter four trans is a five speed four plus an overdrive np2500. im still trying to figure out why the following is happening and having no luck. this is whats happening i park the rig facing three blocks of downhill. i always warm the truck up when i start it up and once it is warmed enough i put it in neutral and take off the brake. it starts coasting downhill and i dont have my foot on the accelerator. almost immediately the motor rpm goes up to about 2000 rpm on its own. when i reach the stop sign i come to a complete stop at which point the motor just as suddenly drops back to a normal idle. the motor will race like this whether or not im coasting forward or backing up. candidates for the problem at this point are 1. a stuck throttle cable ive verified that it isnt though 2. broken motor mount i looked and its not 3. smec single module engine controller is causing the ais automatic idle speed motor to act weird for some reason. this can be caused by a bad a. throttle position sensor b. oxygen sensor doubtful c. d. bad smec any other ideas this one even throws the guy at the dealerships service department. tia. -- john corliss .
Replies:
From : john corliss
john corliss wrote engine is a 2.5 liter four trans is a five speed four plus an overdrive np2500. oh yeah 2-wheel drive too. im still trying to figure out why the following is happening and having no luck. this is whats happening i park the rig facing three blocks of downhill. i always warm the truck up when i start it up and once it is warmed enough i put it in neutral and take off the brake. it starts coasting downhill and i dont have my foot on the accelerator. almost immediately the motor rpm goes up to about 2000 rpm on its own. when i reach the stop sign i come to a complete stop at which point the motor just as suddenly drops back to a normal idle. the motor will race like this whether or not im coasting forward or backing up. by which i mean coasting backwards. candidates for the problem at this point are 1. a stuck throttle cable ive verified that it isnt though 2. broken motor mount i looked and its not 3. smec single module engine controller is causing the ais automatic idle speed motor to act weird for some reason. this can be caused by a bad a. throttle position sensor b. oxygen sensor doubtful c. d. bad smec any other ideas this one even throws the guy at the dealerships service department. tia. -- john corliss .
From : peterdpeterd
on sat 08 mar 2008 201206 +0930 jmc nogroupsspam@nojodibody.homeus wrote suddenly without warning mac davis exclaimed 3/8/2008 1050 am on sat 08 mar 2008 075304 +0930 jmc nogroupsspam@nojodibody.homeus wrote getting ready to return to the us after a long hiatus and working out insurance issues. last time i was in the us it was common to drop collision off the insurance policy on older vehicles. was wondering if thats still the case with vehicles getting more expensive to maintain my dakotas a 2001... thanks for any advice. jmc we carry full insurance until our trucks are paid off then go to liability only.. works for us.. mac please remove splinters before emailing mine was paid off when i bought it jmc g the *only* way to go! .
From : fmb
on sat 08 mar 2008 021500 -0800 john corliss jcorliss@fake.invalid wrote engine is a 2.5 liter four trans is a five speed four plus an overdrive np2500. im still trying to figure out why the following is happening and having no luck. this is whats happening i park the rig facing three blocks of downhill. i always warm the truck up when i start it up and once it is warmed enough i put it in neutral and take off the brake. it starts coasting downhill and i dont have my foot on the accelerator. almost immediately the motor rpm goes up to about 2000 rpm on its own. when i reach the stop sign i come to a complete stop at which point the motor just as suddenly drops back to a normal idle. the motor will race like this whether or not im coasting forward or backing up. candidates for the problem at this point are 1. a stuck throttle cable ive verified that it isnt though 2. broken motor mount i looked and its not 3. smec single module engine controller is causing the ais automatic idle speed motor to act weird for some reason. this can be caused by a bad a. throttle position sensor b. oxygen sensor doubtful c. d. bad smec any other ideas this one even throws the guy at the dealerships service department. tia. you realize you really should not do that right g id guess the ais is causing it that the ecm thinks the engine is powering the truck it is getting a closed throttle and then it is confused and trys to comphensate. thats a wag however. part of the reason is that i dont think the ecm knows about the hill... .
From : max dodge
on sat 08 mar 2008 075304 +0930 jmc nogroupsspam@nojodibody.homeus wrote getting ready to return to the us after a long hiatus and working out insurance issues. last time i was in the us it was common to drop collision off the insurance policy on older vehicles. was wondering if thats still the case with vehicles getting more expensive to maintain my dakotas a 2001... thanks for any advice. jmc though the actual values and rules vary by state id say it is really how much do you want to self-insure if the worse happens you slide on ice total the truck can and are you willing to replace it i think that you hit the nail on the head here but replace it with what that insurance payoff isnt going to amount to much due to the age of the vehicle and they are going to jack his payments thru the roof on the next one if he reports it and attempts to collect. -- if at first you dont succeed youre not cut out for skydiving .
From : tom lawrence
on sat 08 mar 2008 202359 +0000 christopher d. thompson nospam@nospam.nospam wrote on sat 08 mar 2008 023814 -0500 tom lawrence wrote perfect. thank you very much that was right on. did it and my passengers have their power windows back! again thank you. wanna come over and do mine too ^ you might even get tom to let you use the garage........ gbmfg well........just from reading what he writes here i doubt hed let me near his truck. he seems to have a mechanics knack. me i have a a nack for messing up anything mechanical. but i did take my time with this jumper and i even used real connectors to jump it instead of a knife and electrical tape. .
From : john corliss
tom lawrence wrote any other ideas this one even throws the guy at the dealerships service department. well as an experiment id disconnect the speed sensor. i think on your truck its in the tailshaft of the transmission rather than on the rear differential but look in both places for a two-wire connector. disconnect it your speedometer will stop working and do your downhill coast again. this will determine whether its an electrical or mechanical problem youre chasing because without the speed sensor the computer has no way of knowing if youre coasting or sitting still. tom thanks. that makes sense to me. ill give that a shot and report back. may take a little while for me to get at it though. right now im nursing a whiskey hangover. i didnt drink too much. really. oww. -- john corliss .
From : john corliss
fmb wrote john corliss wrote snip i put it in neutral and take off the brake. it starts coasting downhill and i dont have my foot on the accelerator. almost immediately the motor rpm goes up to about 2000 rpm on its own. when i reach the stop sign i come to a complete stop at which point the motor just as suddenly drops back to a normal idle. snip what happens if after you warm up the engine you put it into drive release the brake and coast down the hill as max dodge pointed out its a five speed manual. 80 -- john corliss .
From : john corliss
peterd wrote on sat 08 mar 2008 021500 -0800 john corliss jcorliss@fake.invalid wrote engine is a 2.5 liter four trans is a five speed four plus an overdrive np2500. im still trying to figure out why the following is happening and having no luck. this is whats happening i park the rig facing three blocks of downhill. i always warm the truck up when i start it up and once it is warmed enough i put it in neutral and take off the brake. it starts coasting downhill and i dont have my foot on the accelerator. almost immediately the motor rpm goes up to about 2000 rpm on its own. when i reach the stop sign i come to a complete stop at which point the motor just as suddenly drops back to a normal idle. the motor will race like this whether or not im coasting forward or backing up. candidates for the problem at this point are 1. a stuck throttle cable ive verified that it isnt though 2. broken motor mount i looked and its not 3. smec single module engine controller is causing the ais automatic idle speed motor to act weird for some reason. this can be caused by a bad a. throttle position sensor b. oxygen sensor doubtful c. d. bad smec any other ideas this one even throws the guy at the dealerships service department. tia. you realize you really should not do that right g id guess the ais is causing it that the ecm thinks the engine is powering the truck it is getting a closed throttle and then it is confused and trys to comphensate. thats a wag however. part of the reason is that i dont think the ecm knows about the hill... as tom lawrence suggested the speed sensor should be the only way the truck could know its moving. im going to try disconnecting it and see what happens. also the ais could be broken. -- john corliss . 222 343285 fr18c30m4v@e2.guy.com thank you for taking the time to reply. i sincerely appreciate it. the website you referred me to is great for people doing restoration projects. unfortunately they dont have what i need. depends on how much you want to spend check with www.justdashes.com -- message posted using more information at http//www.talkaboutautos.com/faq.html .