SR20DET RPM drops problem? It's driving me crazy :(

[Charsiu]

Hey guys,

I just finish my redtop swap in my s13.
The car drives fine and everything seems normal, except a RPM problem.

But I have a very serious RPM drop problems keep bugging me and I couldn't figure out what's the problem.

Before I did my redtop swap, a similar problem also happened on my KA24DE after I replace the stock flywheel with a lightweight flywheel, the car will stall whenever I brake and depressing the clutch when stopping. And now, my SR did the same thing to me again.

The car will drive and keep idle well once it start up.
But whenever I try to do a rolling stop, braking with my clutch-in, the RPM will drop below where it idles (800rpm) and die out. It's very annoying for my daily driving.
It doesn't matter if I am rolling stop or downshifting every gear to keep the RPM up, the car will stall at the very last second once I put it in neutral.
When I do a rolling stop, and I don't keep depressing the clutch (only put gear in neutral), the RPM will still drop but it wouldn't stall the car (although very close to stall, the idle will drop to 100-200rpm and back to normal idle range)
Also, sometime when I start up the car, the car will fire up but the rpm will drop immediately and stall.


Now I used to think it's a flywheel problem because I searched and found a few people having a similar problem after doing a lightweight flywheel swap, it's something related to the tranny releasing the load.
But since it's a stock flywheel and stock clutch on my SR, this problem still occurred, so I guess this could be something else.

I don't know where to start and try to fix this problem, hope you guys can help me out.

It's a s13 redtop sr20det, with stock MAF, stock BOV (recirculated), stock Injectors, stock SMIC, Apexi cone intake, 3" elbow and downpipe, walbro fuel pump, stock cat, stock exhaust, stock ecu, everything else is stock.
The compression is good and water pump, seals, spark plugs, belts, fluid.. etc etc has been replaced.


Update:
Just test drive it a bit more, the car now die on every single stop :( No matter the clutch is in or not.
Also the idle is very rough and unstable now, jumping from 500-1000rpm when the car is warm up.
And the A/C button keep blinking and A/C stop working once the car warm-up.

The car idle and drive normal when it's cold, but it gets worse once warm-up.

Problem ghost is haunting me.


Thank you very much.

[slider2828]

Try this, at stable idle.... Pump your breaks. Does you idle fluctuate a lot? It might be a leak in your brake booster. Its definitely a vacuum issue.

[Charsiu]

Try this, at stable idle.... Pump your breaks. Does you idle fluctuate a lot? It might be a leak in your brake booster. Its definitely a vacuum issue.

It doesn't affect the idle when pump my brakes. But it does affect the idle a bit when I just idling and press in the clutch.

I guess I have a very bad vacuum leak?...

[Ceepo]

Its your brake light, when you press the brake the lights come on, causing a draw of power, and the alternater has to send more power out causing the motor to bog down for a second, all my freinds swap's do this, my swap does this...

Do you have electric fans, if you do when they kick on does your motors rpms drop down for a second...

someone correct me if im wrong but thats all i can figure for my car doing this, along with the 6 or 7 of my freinds with sr20dets doing the same thing...

[slider2828]

Sounds like your alternator is going out or your battery. Take both out and go to autozone or kragen and get it tested for free.

[g6civcx]

Recirculate your bov and check all your vacuum hoses.

[0wn3r]

your vacuum can be at 19inHG, but even then you'll probably still have the problem (like i did). the most logical so far was the alternator. i know having the KA a/c on full blast which is mounted to my SR, it does the same thing from time to time. one thing i've thought about is a grounding kit, but i dunno. my power fc took care of it quite a bit too (probably because a higher clutch-in idle), but not 100% fixed.

[Max_PSi]

Your engrish is a little spotty, so let me get this straight. The KA had a lightened flywheel and now your running the stocker after the swap?

I was going to say your flywheel at first due to less inertia. Depressing the clutch while coming to a stop would release the load on the drivetrain causing your RPM's to drop too much. As a side note, coming to a stop while not in gear is not a very good practice. You don't have control of the car if your not in gear, which makes it difficult to avoid last minute shit that would occur.

How do you have the BOV setup? Is it re-circulating or atmospheric? If its atmospheric your MAF may not being see the amount of air flow it needs to keep the car running.

[Charsiu]

Your engrish is a little spotty, so let me get this straight. The KA had a lightened flywheel and now your running the stocker after the swap?

I was going to say your flywheel at first due to less inertia. Depressing the clutch while coming to a stop would release the load on the drivetrain causing your RPM's to drop too much. As a side note, coming to a stop while not in gear is not a very good practice. You don't have control of the car if your not in gear, which makes it difficult to avoid last minute shit that would occur.

How do you have the BOV setup? Is it re-circulating or atmospheric? If its atmospheric your MAF may not being see the amount of air flow it needs to keep the car running.


Sorry with my bad engrish

And you are correct, the flywheel on my SR setup now is a stock one. On my KA setup, the lighten FW will release the load significantly when I depressing the clutch, however I couldn't notice any big RPM drop on my SR setup.

Also, I couldn't figure out how to coming to a stop not in gear? My friend said the same thing to me but I just couldn't find a way not put the car in neutral when I need to stop? Even though I down shift, H&T to keep the RPM up, the last second I still need to put the car in neutral when it comes to full stop? Or at least clutch-in and put into first gear, and the car will die at that very second :(... It's not like I try to rolling stop at every stop sign or red light...

But it's no longer the problem now, the car stall on every stop no matter I am in neutral, only clutch-in or just braking, as long as it slow down, the car will stall, unless I keep revving and pump my RPM up.

My Bov is stock with stock SMIC, so it's recirculating.

[johngriff]

Sounds like the master cylinder is going bad to me.

Brake lights draining the alt? That means it should be REALLY bad if you turn the head lights on... I mean, disconnect the brake lights and check.

[Ceepo]

Its the brake lights, when you press the brake it sends power to the tail lights, the alternator cant keep up with the power that is drawn so the motor bogs for a second till the computer tells it to bump the rpms up to recover... i have this same exact problem on my car, when my electric fans kick on and my car isnt under a load(if its just idleing) the cars rpms will drop for a second and then the motor will recover and be fine...

[Charsiu]

Its the brake lights, when you press the brake it sends power to the tail lights, the alternator cant keep up with the power that is drawn so the motor bogs for a second till the computer tells it to bump the rpms up to recover... i have this same exact problem on my car, when my electric fans kick on and my car isnt under a load(if its just idleing) the cars rpms will drop for a second and then the motor will recover and be fine...


So how did you fix that? I can't driving around without the brake light after all :(...


And you mentioned all your friends' SR swap did the same thing, are there any cure for this?
My car does have the electric fan, but I can't sure if it affect the rpm when it kicks in, cuz my car just die on every single stop or even die before the car is completely stop if I brake hard.

[j87w]

The taillights alone do not pull enough current to cause a load on the alternator so great that the car will die. The reason your idle drops when you press the brakes is not because of electrical load but because your brakes are vacuum assist. What is the battery voltage when the car is at idle with no electrical load (headlights, fans, ect)? What is it with a load? It sounds like you have a mechanical issue rather than an electrical issue.

[Charsiu]

The taillights alone do not pull enough current to cause a load on the alternator so great that the car will die. The reason your idle drops when you press the brakes is not because of electrical load but because your brakes are vacuum assist. What is the battery voltage when the car is at idle with no electrical load (headlights, fans, ect)? What is it with a load? It sounds like you have a mechanical issue rather than an electrical issue.

I will check that out tomorrow, it's raining too heavy outside right now, thanks!

[0wn3r]

well i dunno about bad, but master cylinder sounds quite viable too

[sc0braj]

i'm having the same problem.. however mine is not related to the brakes because i will just simply step on the clutch while regular driving(normal operating temp) and rpms will decrease and decrease until it hits 0 then boom my cars dead WITHOUT even hitting the brakes... i read on another thread about shitty idling and one of the members said it is the stock FPR.. and if you have a walbro fuel pump or any aftermarket besides the stock FPR you probably will have that happen..

[0wn3r]

{...}it is the stock FPR.. and if you have {...} any aftermarket besides the stock FPR you probably will have that happen..

what?

msglength

[silviasichigo]

You should pull the IACV off clean the gunk out of it, Check the vacuum lines that go to the throttle body make sure they are not cracked even just a little, if so replace them.

How is your EGR all set-up do you have factory hoses going to your valve cover? I mean the hard rubber hoses for the crankcase, blow-by, and to the air filter? If you have soft worn out hoses there when the car goes into vacuum they will collapse and cause the car to die.

[dongoesby]

It doesn't affect the idle when pump my brakes. But it does affect the idle a bit when I just idling and press in the clutch.

I guess I have a very bad vacuum leak?...

Hey, are you Liam?

There are different things could go wrong here. First I say definitely do what said above (alternator and boost leak check). Second, have you changed your fuel pump? Thrid, check if the ecu is throwing any code.

Hit me up from Jeffrey.

[silviadrift87]

i had this problem with my ka and sr. the 2 main things that cause it was a minor vacuume leak and a ground. i added a ground from the motor to the frame and was perfect after that.

[Charsiu]

As an update, I found out this problem only happen when I turn my A/C on.
The Car will run very very rough and unstable, the A/C button keep flashing and blinking.
I can hear some loud "tick" every 4sec from the engine, and the car will stall on every stop :(...

Also my boost seems weird... it feels like big turbo that kick in at 4krpm, I should check my timing again.

[lilrusty]

Its your brake light, when you press the brake the lights come on, causing a draw of power, and the alternater has to send more power out causing the motor to bog down for a second, all my freinds swap's do this, my swap does this...

Do you have electric fans, if you do when they kick on does your motors rpms drop down for a second...

someone correct me if im wrong but thats all i can figure for my car doing this, along with the 6 or 7 of my friends with sr20dets doing the same thing...

all your swaps do this?? yikes!! ive had my sr swap for about 4 years now and ive NEVER ran into this problem. ive also done a couple swaps myself and i never has that problem as well... anyways, check your ground to your battery and intake mani cuz factory grounds on 2 points and might cause idle issues if not grounded correctly or you might have corrosion. add another ground and go from there. also check for vacuum leaks, boost leaks, fuel pressure, and timing. sounds like your bov is not properly recirculated, you have to do this when running a maf. also check if iacv is working properly. clean it out and replace gasket... good luck...

[miklos]

Try another check valve in the brake booster line. It is supposed to be a 1 way valve.

[slider2828]

You bumped a 5 month old thread....

[JSnismo240sx]

I get a ground kit that should fix it like silviadrift87 said...