rev problem.

[240sx .25mile]

ive noticed that every time i come to a stop my engine will rev to 1500rpm and after i stopped for about 2 seconds then my engine will rest at a 700rpm idle. i am not holding the accelerator btw... if i just tap the accelerator lightly and quickly it will shoot up to what ever rpm i rev it to and after i let go it will goto 1500rpm and hold for 2 seconds then drop back to standard idle.

what could be causing this???





*EDIT* by the way it is a 1997 ka24de in a 1989 s13

[MidwestMyriad]

Vacuum leak, throttle plate sticking, it could anything.

[240sx .25mile]

Originally Posted by MidwestMyriad

Vacuum leak, throttle plate sticking, it could anything.

i was hoping i could get a list of things.. ive searched online and cant find anything with my problem. this weekend im going to check my tps and continue to try and find vacuum leaks. ill also clean my whole throttle body. anything else??

[MidwestMyriad]

If you still have the EGR system, clean the hell out of it. Just do a general tune up on the motor, if that doesn't do it, check your wiring, since you don't have the original motor it is possible your problem is electronic.

[s13 @ fullboost]

Sounds like the car has a auto ecu

[240sx .25mile]

Originally Posted by MidwestMyriad

If you still have the EGR system, clean the hell out of it. Just do a general tune up on the motor, if that doesn't do it, check your wiring, since you don't have the original motor it is possible your problem is electronic.

no more egr.
im hoping its just a vacuum leak and i can find it quickly lol.

[240sx .25mile]

Originally Posted by s13 @ fullboost

Sounds like the car has a auto ecu

it was auto, before i bought it. is this bad?

ill swap it with a friends ecu and see if that helps



edit- i want to add, i think its an auto ecu because i dont have to push in the clutch to start it.

why does it rev like this though? auto cars dont do that after they stop.

[ShimiBoi]

i have the same problem. i just put an auto ecu into my manual s13.
s13@fullboost- why do the auto ecu's do this?

[240sx .25mile]

Originally Posted by ShimiBoi

i have the same problem. i just put an auto ecu into my manual s13.
s13@fullboost- why do the auto ecu's do this?

did it do this to you before you put the auto ecu in?

[s13 @ fullboost]

I believe it has something to with it having a auto trans? Most likely something to do with the torque converter. Auto ecu is better IMO don't put a manual one back in. With auto ecu You get better fuel maps and no speed limiter

[240sx .25mile]

Originally Posted by s13 @ fullboost

I believe it has something to with it having a auto trans? Most likely something to do with the torque converter. Auto ecu is better IMO don't put a manual one back in. With auto ecu You get better fuel maps and no speed limiter

yeah true. i only have to deal with looking like a retard when i come to a stop. people look at me like, "why is this kid reving his engine??" on a colder morning before i get to operating temp it revs at 1500 for a good 5 seconds then drops. sooo annoying.

[ShimiBoi]

no i didnt have this problem before i put the auto in. i heard it has better fuel maps from one of my homies and i decided to try it out. what else is beneficial besides the fuel map and no 5th gear rev limiter? do you get better fuel economy? cuz im wasting gas for like 5s sitting at the light at 1500rpm hahaha.

[240sx .25mile]

Originally Posted by ShimiBoi

no i didnt have this problem before i put the auto in. i heard it has better fuel maps from one of my homies and i decided to try it out. what else is beneficial besides the fuel map and no 5th gear rev limiter? do you get better fuel economy? cuz im wasting gas for like 5s sitting at the light at 1500rpm hahaha.

nope. you do not get better fuel economy. well im glad that the reason is just the fact that i have an auto ecu. i will still swap with a friend just to make sure. thanks zilvia!!

[ShimiBoi]

So do we get worse mileage? Haha

[562s13]

you get worse gas mileage due to the auto fuel map. on the bright side you have more torque, no rev or speed limiter. i swapped my ecu to a manual cuz of these outrageous gas prices in LA....

[ShimiBoi]

true...what was your mpg? was it significantly bad? cuz i just put it in today and i havent driven it enough to really notice yet.

[S14steez]

Try replacing valve springs

[herbieS13]

as far not having to use the clutch when starting the car is due to this little switch that its supposed to have, since you did a 5 spd swap the switch prolly wasnt put in, isnt necessary you just shouldnt start it in gear without the clutch pressed in and for the reving issue, give your throttle cables afew tugs to see if its getting caught up or like MidWestMyriad said a throttle plate sticking or vacuum leak

[240sx .25mile]

Originally Posted by herbieS13

as far not having to use the clutch when starting the car is due to this little switch that its supposed to have, since you did a 5 spd swap the switch prolly wasnt put in, isnt necessary you just shouldnt start it in gear without the clutch pressed in and for the reving issue, give your throttle cables afew tugs to see if its getting caught up or like MidWestMyriad said a throttle plate sticking or vacuum leak

so you dont think its the auto ecu? im going to swap mine with a friend with a friend. i did not do the swap by the way. it was purchased like this. ill try your advice this weekend. thanks!

[s13 @ fullboost]

chances are its your ecu

[562s13]

Originally Posted by ShimiBoi

true...what was your mpg? was it significantly bad? cuz i just put it in today and i havent driven it enough to really notice yet.

I was getting horrible mpg cuz my engines running really rich and i didnt have the time to fix it. But wheb i put it in i noticed atleast 6 mpgs morr

[camaro379ss]

try cleaning your IACV. Doubt its a vacuum leak since it doesnt stay idling at 1500. And yes clean your throttle body.

If its not those then yea its your ecu.


I know on newer nissans this is considered normal due to fly by wire throttle, but not here since obviously its cable.

[240sx .25mile]

Originally Posted by camaro379ss

try cleaning your IACV. Doubt its a vacuum leak since it doesnt stay idling at 1500. And yes clean your throttle body.

If its not those then yea its your ecu.


I know on newer nissans this is considered normal due to fly by wire throttle, but not here since obviously its cable.

im gonna try the ecu first. i really dont want to do the iacv lol. kind of a pain. and ive been trying to hunt down a vacuum leak but i cant find one.. i want to clean the throttle body and make sure my tps is adjusted correctly just for shit and giggles.

[camaro379ss]

Its really not that hard. And you probably wont find a vacuum leak because thats not the characteristics of a vacuum leak. But yes start with the throttle cleaning and if you have access to a free ecu to test then yea go ahead and do that too.

[240sx .25mile]

Originally Posted by camaro379ss

Its really not that hard. And you probably wont find a vacuum leak because thats not the characteristics of a vacuum leak. But yes start with the throttle cleaning and if you have access to a free ecu to test then yea go ahead and do that too.

yeah about the vacuum leak, i sprayed a whole can of carb cleaner and got nothing haha. thank god.

and btw, my ecu is a number 31. which means, 1991 auto. i have 2 free ecus and 1 ecu for 20 just incase the 2 do not work. thanks for taking your time and helping me camaro

[camaro379ss]

Nice so that will be quick to either rule out or fix good deal.

[ARBEE25.s14]

I'm having a similar issue on my RB25 & TJ ECU. It's weird, mine will idle at about 3K until i turn the car back off, let it sit for a minute then turn it on and it will idle fine....I hate that is pwning my gas when im just sitting at a red light.

Let me know what you do to fix yours.

[camaro379ss]

^^^That's a bit different scenario. What have you tried on yours so far?

[ARBEE25.s14]

Originally Posted by camaro379ss

^^^That's a bit different scenario. What have you tried on yours so far?

I've tried adjusting the IACV screw, adjusted the TB screw, I've tried resetting the TPS, checked for vacuum leaks (none). I guess the next step would be to take off my IACV and try and clean it.


The purple electrical connecter that goes to the IACV sort of broke when trying to connect it. Not sure if this would have anything to do with it....

I hope you get it fixed so i can try what you do. If i fix it i'll be sure to let you know as well.

[240sx .25mile]

Originally Posted by ARBEE25.s14

I've tried adjusting the IACV screw, adjusted the TB screw, I've tried resetting the TPS, checked for vacuum leaks (none). I guess the next step would be to take off my IACV and try and clean it.


The purple electrical connecter that goes to the IACV sort of broke when trying to connect it. Not sure if this would have anything to do with it....

I hope you get it fixed so i can try what you do. If i fix it i'll be sure to let you know as well.

does your tps work?

YouTube - 240sx How to check & test your TPS Part 1 www.240SXTECHDVDS.org 1080 HD KA24DE.mp4