S15 problems

[specR_s15]

Hi All,

I've been having problems with my s15 lately. It's a problem that goes away and then comes back after a few weeks/months.

Symptoms:
- After a long cruise the car will start to drive rough, revs would go up and down both while cruising or idling. Even worse when idling, as it feels like the car will stall.
- While cruising and trying to boost/floor the car, it will not rev up (past 2000-3000rpm), feels like it has trouble reving. It blows black smoke at the exhaust, backfire (I'm tied of cleaning the exhaust tips)

When i let the car sit (engine off) for an hour or two it drives normal again, but weeks later it comes back.

I've serviced the car, changed plugs, checked for boost leaks, cleaned TB and AFM, set BOV to plumback and still having the issue.

Can someone please help me out?

Car Specs; JDM, PFC, Greddy FMIC, 040 fuel pump, 740 injectors, spitfire coils, turbo back xforce system with stock cat, hks filter, GFB BOV, greddy profec boost controller, greddy turbo timer.
Just serviced the car 2 weeks ago with new z32 bigger fuel filter, royal purple oil, spark plugs.

cheers

 

[LuPix_S15]

I'm siding towards a coilpack problem... you've done the plugs but maybe coilpack(s) failure would cause all the lumpy idling, loss in revs/power and black smoke due to fuel not being burnt properly?

I'd say the best way to check is to get the spark cover off, driver her hard until all your symptoms are back... then remove one coilpack at a time (not sure whether you can do this whilst car's running so someone confirm lol!!)... if removal of one coilpack does not make the car any worse then it's gotta be that coilpack failing.

Also coilpacks get worse with heat so maybe that's the reason why it's only happening when car is nice and warm/hot.

I'd start by checking the coilpack that's nearest the bulkhead as well

 

[Toby]

X2

 

[specR_s15]

So while the car is idling, i unplug each of the coilpack wires one by one to see which one is faulty? Wouldn't the car stop?
Do i need this do this check only when the symptoms are back or can i do it if the run is running normal again?

 

[sx-si]

i think its a heat issue or electrnic tbh,
seems like either you coil packs are breaking down when its getting hot under the bonnet

or theres a issue with the map

or both

 

[LuPix_S15]

So while the car is idling, i unplug each of the coilpack wires one by one to see which one is faulty? Wouldn't the car stop?
Do i need this do this check only when the symptoms are back or can i do it if the run is running normal again?

Well basically it's only one coilpack that usually fails... I gather if two or more fail the car will be fooked and undriveable lol!!!


Still not sure whether you do this when running but to be on the safe side fire the car up and drive her until the symptoms start again... then stop the car, remove coilpack nearest bulkhead. Fire her up again. If the car is worse than before then you know that coilpack is working. If it's exactly the same then it's most likely not firing properly and needs changing.

If it gets worse then replace that coilpack and move onto the next. Again stop the car to do this. If you remove second coilpack (but ensure the first one you removed is back in!) and problem gets worse then that coilpack is ok but if it stays the same then that coilpack needs changing etc.

So it works by process of eliminiation:

PULL OUT COILPACK -> CAR RUNS WORSE = COILPACK OK
PULL OUT COILPACK -> CAR RUNS SAME = LIKELY COILPACK FAILURE

 

[specR_s15]

thanks guys, i will try the coilpack checking this weekend.

BTW, here are some pics of my sparkplugs a day after the symptoms appeared. These were brand new plugs 2 weeks ago. NGK-R BKR7E (comes pregapped to .8 i think)

One more thing, i got this BILLION VARIABLE FAN CONTROLLER with the car and i'm wondering what the LOW & HIGH setting is?
LOW & HIGH as in how fast the fan turns? What should i set it on?

thanks

 

[snackbox]

I would be aiming towards coil packs as well see if you can borrow some even and swap them take it for a drive if all is ok buy new ones.

 

[S15AK]

I would say coilpacks as well, but carefully check each spark plug, as I had a hairline crack in one of mine and it missed it. This only effected the car on high boost though, but I'd still double check each plug if I was you.

 

[snackbox]

Your plugs also look fairly black, I wouldnt know how to go bout loookin into that but mine arent that black after a month :\..

I also prefer iridium plugs id never use any other in an s15

 

[Auss15]

I'll throw another one into the equation, the O2 sensor.

 

[japmadlad]

you check the coilpacks with the engine running. it wont damage the car

 

[RyanH]

seems like either you coil packs are breaking down when its getting hot under the bonnet

or theres a issue with the map

or both

:nod: I'd go with replacing the coilpacks. I dont think the splitfire replacements are too expensive :thumbs:

If you're only getting a misfire when boosting at 3000rpm, surely the car is gonna sound rougher if you remove any of the coilpacks while idling? When my coilpacks died on my S14, the car idled fine!

I use BKR7EIX in my SR20s - never had a problem.

 

[lvaleiron]

just trowing something out there... you mention you cleaned the AFM, but did you try to switch it for another one? A faulty AFM can lead to these problem, and i've seen intermitent problems with AFM.

 

[specR_s15]

I've removed the spitfire coils and put back my standard coilpacks, it's been a week and the car has not had the problems. (touch wood)

Btw, is it a bad idea if i have my rad fan running all the time?Pros/Cons?
I have a fan controller and i've set it to run at low temps, so pretty much when my car has warmed up it's on.

cheers

 

[Yakozan]

Could very well be the AFM on it's way out too. Have a similar issue with my Impreza STI and I'm pretty sure it's the AFM.
Next time it idles bad, you could try jerking the AFM cable around a bit. It usually sorts my STI out for a while lol

So either Coilpacks, AFM or O2-sensor. Usually it's the coilpacks, but this time I actually think it's the AFM. I would try to borrow another one and see if the problem goes away.

 

[sliding-r]

Your plugs look to be in a too rich environment unless there is a misfire caused by a weak spark.. It looks to be all plugs so I would check earths on the back of the head for the coils first before expecting it to be coils themselves.

But the map could be too rich causing the plugs to foul.. I would get another cheap set of plugs and if it cures it then you need the car mapped to correct afr's..

 

[sliding-r]

Second yakozan, You can clean the afm also with carb or brake cleaner, this could cause these symptoms aswell.