Duffed Dub

I knew the car had a misfire when i bought it. i walked out today to mess with it. now with a fresh battery early in the morning the car started and ran fine. i drove it around and once it got to the lower end of the normal running temp did a few 1-2 pulls and the car was great. hit boost well, no stumbling. nothing. until about 10 minutes after it got to running temp. it started getting a slight misfire around 2k rpm but cleared up past 2500. which progressed into the car idling rough and if i touched the gas pedal it would just spit and pop and never make it past 1k rpm. i red that it could be the ECU coolant temp sender. was able to track one down and swap it but had the same issue, checked the alternator and i was getting 13.2 volts. low but still charging so i hooked up jumper cables from another running car and same issue. i also noticed at this point im not getting any aux power to the cluster, power windows, sunroof, or even heat blower. but while i was sitting in the car bashing my head into the steering where i saw the cluster had power. which immediately was lost as soon as i tried to start the car. it still starts when hot, just idles rough and wont go past 1k. if i park it overnight i get to do the same thing all over again. runs fine cold and then a few minutes past running temp it sinks faster then the titanic.

i tried to ask for help on a local s chassis page and they told me it was a boost leak.

any ideas? this is my first Japanese car. im coming from my VW cult.

brndck

ok you need to do some actual testing.

- theres TWO coolant temp sensors. one is for the instrument cluster. one is for the ECU. which one did you replace?

-what ecu are you running? what modifications are done to the engine? have you checked compression/leakdown? have you done a test for blown head gasket? is there white/grey/black smoke out of the exhaust? what do the plugs look like?

TONS of shit you should be checking, and you def need to fix that alternator before trying to further troubleshoot.

__________________

http://outslidersandsmokeproduce.blogspot.com/

Duffed Dub

i replaced the temp sender for the ECU, sorry for not clarifying. it was the one with 2 wires going to it.

the engine is a bone stock S13 SR with the emissions deleted. has the heat fins on the head indicating it was a later red top. the ECU has the number "62" on it. not sure what that means. i though i took a picture of it but cant find it. will run out right now and get a picture to post. i have not done a compression test or leak down because the motor is not smoking and runs fine when you fist start it up. theres no oil or exhaust fumes on the radiator. the motor had 26k when swapped in and the last owner put 6k on it. the plugs were recently replaced so i couldnt really guage much off of them. they looked brown, but nothing unusual. previous owner also replaced igniters with new OEM ones in an attempt to solve the problem.

side note i also tried to pull the codes from the ECU, but when the dash does have power there is no check engine light and the diagnostic mode doesn't give any codes.




*EDIT* here's the ECU
https://photos.app.goo.gl/CNRiRa3BkG5BwNs2A

NashT

I saw all emissions were deleted, but does that include egr and iac? You need to check vaccum lines if your still running any beyond the booster line.

You def need to do some hard trouble shooting with a test light and meter to see why your cluster is loosing power, may be a pigtail not fully seated or even a loose body ground.

Are you able to do a fuel pressure test? Weak pumps get worse when the pump motor gets hotter which would cause a misfire.

As far as the ECT, I think your good there if its not having trouble starting hot. You can actually graph that to see if its functioning correctly. Colder temp will have lower resistance, hotter would have more.

Finally if you are not able to pull codes, thats usually an indication of a bad PCM/ ECU.

brndck

sr20 doesn't have EGR,
boost leak wouldn't be different when cold vs when hot
if you have a fuel pressure gauge, it would def be helpful to monitor when its "cold" and running fine vs when its "hot" and wont rev past 1k

if you're losing power to the cluster and windows, etc, i'm really leaning toward this being a charging/alternator issue. its pretty easy to remove it and take to napa/autozone and have them test it for you. its free.

__________________

http://outslidersandsmokeproduce.blogspot.com/

Dboyizmlg

The very first thing you should do, is a compression test with throttle open.

Make sure you at least getting 145-160 across the board.

Then if that’s good, you have a misfire in a cylinder, you can usually tell by the plugs which one is misfiring.


Report back after that

NashT

Also 13.2V is plenty to run a 12V system, sure its undercharging a bit, but that would not cause your intermittent power issue in the cab.

You need to start with the basics first, check fuses and relays, look for corrosion, etc. But sounds like you have a short, check all your body grounds especially the interior ones.

Your in cab electrical issue is most likely a separate problem from the misfire.

Start troubleshooting one issue first instead of jumping around.

Duffed Dub

lots to reply to but after work i had to fix the oil pan on my MK4 VR wagon because its my daily and i need it. but after that i was able to mess with the S13, didnt get as much done as i wanted but i learned a few things.

fist of i fixed the lack of power to anything problem! while in the engine bay i found a huge wad of electrical tape. if i poked that wad id regain power to the interior for .03 seconds. pulled all the tape off it and the deeper i got the crisper and stickier it got until i found this:

https://photos.app.goo.gl/sJiYu15xxQxD4TRH6

i will pick up stuff to fix it correctly tomorrow after work, for now i made sure everything had a solid connection. and it works.

so as of now i have replaced the coolant temp sender for the ECU.

ran into the same problem. car cold starts fine revs smooth, builds boost, etc. i measured the voltage cold at 13.8V. im happy with 13.8. once it warmed up same problem. wont rev past 1k. i measure the voltage again at this point at 12.4V. that really really bad. im not saying the alternator is the problem. but it defiantly needs to be replaced. i picked up another. removed the old one, and couldnt get the SR pulley off the alternator. tomorrow i will get a puller and worst case drop it off at my machine shop to get it taken off.


i'll report back if it changes anything. thanks for all the feedback. i really wish i could respond to each one but it would take me hours.

Duffed Dub

alternator, alternator fuse, and some basic wiring the car is running great. its a little slow to start and almost sounds like its going to hydro lock but its doing well. it backfires and stumbles under load after accelerating after idling for awhile. but if i keep rpms above 3k for awhile it goes away. fresh premium fuel and some lucas injector cleaner helped a little bit. going to check timing next. any ideas on what i should try? im going to do more research on it tonight.

jedi03

try cleaning out iacv maybe?

NashT

Sounds like a fuel issue for sure. Definitely check your timing but if its not running hot you shouldn't be running too much advance. Have you ohmed the injectors or used noid lights on them?

Duffed Dub

i'll give it a shot


the symptoms have changed since sorting the charging system. i dont know what it means to ohmed the injectors or even what a noid light is so im going to do some research haha.

i could defiant see it being the injectors now. since fixing the charging system. i used some Lucas injector cleaner and it seemed to help until the next tank of gas. it just seems to me like a backfire when trying to accelerate right before the turbo spools. like the car is getting too much fuel and has to catch up. it only happens on hot days after sitting at red lights or low rpm. if i drive for abit around 3500 to 4k it clears up quickly. the car is also hard to start. seems almost like its coming close to hydro locking. its turns over a few times, boggs really bad, pops a few times. then idles and runs fine.

i've been practically daily driving the car trying to figure out what causes the quirks

Mikester

Hey how's it going. Glad you got the charging system and wiring sorted out. One of the not so fun parts about this hobby is sometimes having to clean up others' messes. On that note, is there any chance that you or the previous owner used octane booster since the last spark plug change? If so, I would tell you that changing the plugs and never using it again will be the ticket. What you describe in post #12 sounds eerily familiar.

Mike

__________________

z31andrew

Clean IACV and replace all injector o-rings/make sure injectors are seated and sealed properly
I had a very similar problem on my car but after replacing coolant temp sensor, injector o-rings, cleaning IACV and adjusting fuel pressure it cleaned up the idle well.

Presto

Try unplugging your maf sensor while it’s running

blkvrtswp

+1 for injector o-rings. Cheap and easy to replace!

Duffed Dub

just had my OEM injectors refurbished and checked out by the doctor injector 2 hours away. still no change. procured a timing light, checking that tomorrow. whats a noid light?

i have not besides some lucas injector cleaner which seemed like it helped until i ran through that tank of gas. im planning on changing plugs tomorrow

it just starts idling crazy. jumping from like 300 to 800 rpm

got new O rings when i had my injectors rebuilt, still no change.






doing timing and plugs tomorrow. it only happens once the engine starts getting hot anf right before it builds boost it just starts crackling and popping. it could only do that if its getting too much fuel. if the timing and plugs dont fix it i guess i could get an adjustable fuel pressure regulator? would an old FPR cause too much fuel pressure once warm? hopefully i get it sorted tomorrow. really hopeful on the timing being off

Mikester

The fact that it ran pretty well through the tank of gas that had the injector cleaner in it, then went right back on the fritz with fresh fuel is why I suspect the plugs went bad. This happened to me a more than twice until I made the association and stopped using fuel additives altogether. You may be getting the right amount of fuel with insufficient spark. Hopefully plugs will fix it without having to fiddle with timing.

An adjustable FPR is a good thing to have once you start getting ready to tune, but not a necessity for a relatively stock setup. If you do add one, recommend that you have a pressure gauge & wideband handy, to make sure it is getting the right amount of fuel throughout your rpm/boost range.

Mike

__________________

Duffed Dub

timing was way off, had BKR7E spark plugs vise BKR6E for a stock motor. same issue. starts a little better but thats it. if i slowly ease on the gas and dont build boost it will go but if i try to get it to spool it just falls on its face. but only after driving it for awhile at temp. warming up and shortly after it gets to running temp it fine. is also revs fine with no load on it.

id take it to a shop but i dont know any places that would understand it has a sr in it.

Duffed Dub

At what point of the 240sx problem diagnoses process is it acceptable to cry?

Mikester

Have you verified that all of your couplers, boost/vacuum lines & actuator are good?

__________________

Duffed Dub

couplers are good, not sure how to test them but visually all the vacuum lines look good. not sure how to test the actuators either.

its just really strange that it doesnt do it until the cars been driving at temp for awhile.

im making a cross country trip to my hometown in georgia. i might just park it until then and find a shop once i get there. i was already planning on towing it.

Mikester

The actuator is the little bellows mounted on the turbo that pushes the wastegate door open.
You can move it by hand with a little bit of effort. If it’s overly easy to move cold, it may be too floppy at temperature. Other times, the little c-clip that keeps the actuator rod secured to the wastegate comes off & the car will never build boost.

__________________

nick_d_240sx

Have you checked the coil packs? I had a similar problem and it was the cheap off-brand coils. Got new OEM ones and cleared it right up.

__________________
1990 240SX SR20DET GTX2863R

Duffed Dub

it moves but its not easy. when it does build boost it pulls hard and hold 8psi steady


the PO replaced them trying to clear the issue with brand new OEM ones stamped nissan, i borrowed some off mu buddies 300zx that runs fine and still had the same issue

Mikester

Do you have any other peripherals that have vac/boost lines, like BOV, boost gauge or boost controller? Feel like there is something simple causing this. Negative battery cable secure & in good condition? I know I’m asking questions vs. offering solutions, but one small crack in a line opens up when the car heats up, one corroded or bad connection somewhere... could be worth inspecting.

__________________

Duffed Dub

the engine is bone stock besides the intercooler, there is a boost gauge. i can check all the vacuum lines for that again but none appear dry rotted or compromised. i was having power supply issues so i've already gone through the wiring for the battery and alternator. all the grounds are solid. all to raw metal, nothing grounded to paint.

ask away man, i'll take any help i can get

LayNLow

You can’t check for vac leaks by just looking at it. Smoke test your whole system after the MAF and you’ll probably find something leaking.

__________________

z31andrew

Check your Coolant temp sensor. That being bad would indicate rough running at lower temps, as the sensor would not allow the system to run on it's "cold" setting, causing rough running. Until your system warms up, the ECU is already running "at temp" so once it hits the correct temp all would be good.

Definitely would recommend to check that sensor is operating properly.

Jfornachon

One of the best ways to check for vacuum leaks is to spray brake cleaner and see if the rpms change.

have a great day,
jared