240sx Idling low when decelerating or coming to a stop

[marryson]

I know there has been number of posts regarding this stalling problem. the car idle dips very low when decelerating or coming to a stop(foot off the gas). sometimes the car even stalls completely. well guess what, this is happening to my car. but in my particular case, the car was originally an automatic which ran fine without any problems. no stalling no low idling. but after I took it to an auto shop for a 5 speed swap, the stalling problem suddenly appeared. do you think that they might have kept some parts such as the throttle position sensor in automatic and didnt change it to a TPS required for a standard transmission? any help is appreciated

**Update** one thing I should have mentioned is that the car will most likely stall completely when I brake hard from more than 60km/h(40mph). the problem does not occur when I come to a stop from a speed lower than 30km/h.

[camaro379ss]

Why dont you take it back to them and have them fix it should be free if it has been doing this since they performed the swap....unless it has been sometime.

[aznfab213]

this symptom could possibly be the knock sensor.

[marryson]

thats what I did when I got my car back from the swap last year. they couldn't fix it. the car drives fine, it doesnt stall all the time. it didnt bother me at first but I find it pretty annoying now... the auto shop has moved and i couldnt contact them...

[KiLLeR2001]

Do you have a lightweight flywheel installed? This happens to me occasionally so I've pretty much made it a habit to blip the throttle when I come to a fast stop from a high speed.

[marryson]

Do you have a lightweight flywheel installed? This happens to me occasionally so I've pretty much made it a habit to blip the throttle when I come to a fast stop from a high speed.

sorry Im not that familiar with flywheel. could you explain to me how a "Lightweight" flywheel in particular can cause my car to dip low when decelerating? thx

[camaro379ss]

Generally with a lightweight flywheel since it weighs less there is less rotating mass for the engine. A light flywheel can cause the revs to drop faster due to less mass for the engine to spin. So rather than the revs hanging and slowly dropping they now would drop fairly quickly.

[marryson]

Generally with a lightweight flywheel since it weighs less there is less rotating mass for the engine. A light flywheel can cause the revs to drop faster due to less mass for the engine to spin.

oh ic thx. but I doubt the auto shop would swap in a high performance flywheel... they woulda just give me a stock one.

[Ace]

I've had this same issue happen to me. My last 240 was an auto to manual swap and I had the same exact symptom. Took it to all kinds of mechanics and could never figure out what the problem was. My guess is there's got to be a difference in how the idle or throttle is controlled from auto to manual.

That car was totalled by a drunk driver so I bought a clean stock manual hatch and have never had it happen. Same goes for my friend's 240 originally manual. So I don't know what to tell you. Could just be a coincidence. Could be a difference that whoever did the swaps left out or got lazy on.

[marryson]

I've had this same issue happen to me. My last 240 was an auto to manual swap and I had the same exact symptom. Took it to all kinds of mechanics and could never figure out what the problem was. My guess is there's got to be a difference in how the idle or throttle is controlled from auto to manual.

That car was totalled by a drunk driver so I bought a clean stock manual hatch and have never had it happen. Same goes for my friend's 240 originally manual. So I don't know what to tell you. Could just be a coincidence. Could be a difference that whoever did the swaps left out or got lazy on.

hmm interesting. guess I shoulda just buy a stock manual instead of swapping it..... now I gotta find that shop and get it fixed......

[Ace]

hmm interesting. guess I shoulda just buy a stock manual instead of swapping it..... now I gotta find that shop and get it fixed......

I'm sure not every swap has this problem. But it seems to be common enough to look further into it. Taking it back to the shop seems like your best bet considering they did the work and shouldn't charge you for the repairs

[marryson]

I'm sure not every swap has this problem. But it seems to be common enough to look further into it. Taking it back to the shop seems like your best bet considering they did the work and shouldn't charge you for the repairs

just found this thread somewhere. do u think its the ecu? maybe I need an ECU for 5 speed? or are they the same?

[ShimiBoi]

I have a manual s13 that came manual stock, with the manual ecu and this happened to me too. I had a couple vacuum leaks from old hoses cracking that I fixed and I did a couple other things to clean up my motor, seafoam'd it, cleaned tb, cleaned maf, got new tps pigtail, etc. So not really sure what fixed the problem, but it just went away. No lightweight flywheel either. Hope u fix ur problem.

[marryson]

I have a manual s13 that came manual stock, with the manual ecu and this happened to me too. I had a couple vacuum leaks from old hoses cracking that I fixed and I did a couple other things to clean up my motor, seafoam'd it, cleaned tb, cleaned maf, got new tps pigtail, etc. So not really sure what fixed the problem, but it just went away. No lightweight flywheel either. Hope u fix ur problem.

how was your idle tho? is it completely fine? does it only stall when comming to a stop especially during hard braking? where are the vacuum hoses and how much was the tps pigtail? thx for ur help:wan:

[marryson]

Update! This afternoon I decided to check on the tps. so I disconnect the tps harness and went for a drive. a little high and a little low some times on idle. but hey! the car wont stall even during hard braking. the car responds normally during deleration. heres the interesting part. the when I plug the tps harness back in, the stalling problem is completely gone! Im suspecting this is just temporary but I guess I found the problem.

[ShimiBoi]

how was your idle tho? is it completely fine? does it only stall when comming to a stop especially during hard braking? where are the vacuum hoses and how much was the tps pigtail? thx for ur help:wan:

I got the pigtail from the junkyard for free (pocket) shuldnt run you more than $3. Check your egr, sometimes when your egr gets old the diaphragm doesn't hold pressure so it either gets stuck open or stuck closed. Usually gets stuck open that's why it dies when coming to a stop. That's how mine was. I think I had a vacuum leak near the egr. Replace the vacuum lines around the egr cuz alot of times they start cracking. Might as well replace them all while you're back there. My car would die coming to a stop and at idle. Sucked balls getting off the freeway with no power steering haha.:duh: g'luck fixing it and let us know how it goes nd what u found out.

[marryson]

I got the pigtail from the junkyard for free (pocket) shuldnt run you more than $3. Check your egr, sometimes when your egr gets old the diaphragm doesn't hold pressure so it either gets stuck open or stuck closed. Usually gets stuck open that's why it dies when coming to a stop. That's how mine was. I think I had a vacuum leak near the egr. Replace the vacuum lines around the egr cuz alot of times they start cracking. Might as well replace them all while you're back there. My car would die coming to a stop and at idle. Sucked balls getting off the freeway with no power steering haha.:duh: g'luck fixing it and let us know how it goes nd what u found out.

it could be the tps. im pretty sure. cuz I tried driving with the tps harness unplugged. the car didnt stall or low idle when decelerating. and after that when I plug it back in and go for a drive. the problem just disappears. it might be temporary but its fixed for now. I been driving all day long. no stalling :redxd: I'll keep this post updated when something happens.

[camaro379ss]

It almost sounds as if it may be out of adjustment or going bad. I would do some back probing and post some resistance numbers up of:

Completely released
Partially released
Completely depressed