RB25DET weird idle/stalling issue. Please help!!

[pinkpandaslide]

Ok, I have done lots of searching about this issue and tried them but this issue have me lost and confused so maybe someone out there can help me out.

RB25DET in S14. Stock injectors, turbo, etc. Only has FMIC and Freddy type bov. The car was running fine and the maf seemed to have gone bad since it would idle fine and then wont pass 2500. Had a z32 maf and safc laying around. Installed it. Put the 2in 4out settings and got it running and idling good.

Here's the problem:

-Car would idle nice and solid with no fluctuations. Drove good until you would roll to a turn or slow down to a stop. Then the car would feel like the maf was choking or something. It would feel like it wants to stall and if I try to give it gas, the rpm doesn't respond to the throttle and needle wont move. Then the car would stall. Sucks coz this only happens about 20-30 secs of driving and the car would not want to start back up. Just cranks and cranks and won't turn over. I have to push it back home :rant:

After I get it home, of course I need me some rest for a few hours and then I go back out and try to start it and it starts and idles fine again but when driven same issue again.

Ditched the z32 maf setup and safc and installed a good stock rb25det j60 green label maf. Same issue. idles decent, drives decent then chokes to stall. Won't start back up until a few hours.

I have checked for boost leaks by spraying the couplers etc with water and rpm dont change. Made sure all coupers to piping is good and tight. Checked vacuum lines and it goes this way:

Front of intake manifold nipple- fpr line
Two intake manifold nipple on side by throttle body - bov and boost gauge.
Big one in the back of intake mani-brake booster
Little nipple in the back is plugged.
Throttle body nipple is plugged.
Wastegate line is connected to hotpipe nipple.

Bov is not recirculated.

Any ideas guys? Thanks for any help.

[smoked240]

I would recirculate your BOV for starters. When I had mine vent to atmosphere with a maf sensor, I came to a stop or slowed down and it would shut off..but it would usually start back up. While your car is running unplug the maf and see if anything happens.

Before I went standalone I had the exact problem you had and it turned out to be my O2 sensor. I'm not saying it's the same case with yours but its worth a shot if it hasn't been replaced. After it shut off it wouldn't start for an hour or so.. Unless I unplugged my maf and cranked it a bit, plugged the maf in and it usually fired right up for some reason. My bov was circulated while this was happening.

[pinkpandaslide]

ill check on that. When car is running and i unplug the maf, it stalls. Im running a innovative lc1 wideband if that helps. also, when i had the z32/safc set up on. i noticed that when i try to put a value on ne1, car stalls right away.

Also, idled the car today, it hunts for idle and wants to stall unless i give it gas rev up and then idle gets steady. i do notice that when idle drops, so does the vacuum pressure. not sure where else to check for vac leaks. also unplugged some things while idling to trouble shoot.

tps: disconnect connector to it . no change to rpm. disconnect the plug with wires leading to actual tps, there is change in rpm.

aac/iacv- unplug the brown plug, there is change. unplug the purple no change.

coolant temp sensor-no change

car idles steady and pretty solid with some signs of rpm drop when vac drops. revs freely nicely though.

any other suggestions?

[pinkpandaslide]

i got the idle sorted out and idling real nice. it does stall when i let off gas revvin'. i can hear a sound coming from the turbo area. i guess it has a turbo leak. i gotta check today.

[pinkpandaslide]

found a loose turbo flange bolt to manifold. tightened that. got the car idling really nice and revvin freely for about 30 mins. drove it down the block and what do you know, dead again! had to push it back home. Put new coolant and new coolant temp sensor. Still same issue. Any other suggestions?

[feito]

Bov, did u try it???

[pinkpandaslide]

recirculating the bov is next. just have to make a bung to connect the hose to in the intake pipe. its so weird tho because usually if its some kind of leak, specially if its minor, the car will try to fight and struggle. this problem is smooth idle, smooth rev, and smooth drive for the 30 secs down the street before everything seems to just shut down. no choking anymore or any weird bogging. just like your at about 2-2500 rpm cruising down the street at 2nd gear going about 15mph. then all of sudden you feel the car about to shut down, you try to give it gas but it doesn't react or respond. then car shuts off and then car will just crank and catch to turn over but wont start and idle. then push back home. wait few hours to let it cool down and idles and revs perfect again and repeats itself once you drive it.

[feito]

^wait, nvmd with the bov then, i though it was only during coasting...

[pinkpandaslide]

i think i found an issue last night. checking the fuel pump relay, one of the wires were loose on the connector. im thinking it must be when the car is moving, there is vibration and movement causing the wire to loose connection. will see in a bit if it fixes it *crosses fingers*

[pinkpandaslide]

ok checked compression. 150 all across. checked fuel pressure. 46psi static and 37psi idling.

i did notice that when my ignition is on, the fuel pump stays on and never shuts off. you think this could be an issue?

regardless, from diagnosing this thing, what's consistent is that the car will die as soon as i drive it down the block and won't turn back on until the temperature is cold. it has no problem idling and revvin until its to normal temp and i have done it for atleast 30 mins.

i did install a new coolant temp sensor as well as topped it off with coolant. i did notice that the upper radiator hose doesnt get hard. does that mean thermo not opening? could this affect coolant temp sensor and putting it to limp mode or some kind of safety shut off on the ecu to protect car?

i might be getting close. but then again who knows lol. any other suggestions and help would be appreciated. thanks

[pinkpandaslide]

UPDATE**was able to reproduce the issue in the garage a few days ago, it was the o2 sensor. changed that with a new one. car was better and was able to drive around my neighborhood. noticed that it bogged when it was cold and drove fine when hit normal temp. didn't stall anymore!!! =) so i installed new z32 fuel filter. as well as put the z32 maf back on. idled and drove well around the block with no issues. pulled in the garage n idle was around 1k so i unplugged tps n adjusted idle screw. got it to 850-950 n plugged tps back in. i turned the car off n turned it back on. now wont idle unless i give it gas. messed with the idle screw and tps again. using safc voltage readings on sensor check, i adjusted tps voltage to .45v on static and 5.0v on wot. still same thing. hunting idle after i give it gas to start.

what you guys think. i unplugged battery to reset ecu overnight and will try again tomorrow. thanks guys.

[smoked240]

Yeah that's pretty much the same problem I was having..my o2 fixed what yours did too. I still had the same issue, it wouldn't drive right until it was warmed up.. I almost want to say it was my ecu but I can't verify that 100%. Once I went standalone and had it tuned it runs like a dream. It could have been my maf also..I would suggest any kind of ecu with a proper tune. That stock ecu limits the power of the rb25 so much..

[pinkpandaslide]

Well, it did it again this morning. Same thing. Seems like everytime I turn it on after a good break, I can give it gas to idle and maybe high at times but idle nonetheless. Let it warm up and drive it and its fine but as soon as I park it and shut it off, the problem starts all over again once I turn the car back on. Then its adjusting idle screw to get a good idle and then it will repeat problem once I shut the car off. I'm starting to lean towards an ecu tune since it seems that rb25 ecu is really sensitive and always going on safe mode or something. Any other suggestions you guys think I should check? I'm ready to pull a trigger on an ecu tune from enthalphy hoping it will get everything all fixed.

[pinkpandaslide]

cleaned aac/iacv and checked tps, o2, coolant temp sensor for connectivity from connector to ecu as well as ohms testing on the sensor. all checked out. started it, it didnt hunt for idle and idled pretty solid. drove car and same thing. rolling down the street with about 10-15mph. light throttle, then car cuts off and dies. you feel it start to loose its power and about to stall. put gas to rev up from stalling but needle dont response. then car dies and wont start back up. don't even want to turn over just low rpm like 300ish crank and crank. =(

[pinkpandaslide]

its starting to feel like its coolant temp sensor related still. even though connectivity from connector to ecu is good. voltage in the harness is good as well. put a new ka coolant temp sensor on there. maybe its the wrong replacement sensor i put. i noticed today that when the car died after good idle and warm up, it died as expected. then i would start it back up and it just cranks and not turning over. i unplugged the coolant temp sensor and the car cranked and started up for a brief second and it stalls. atleast with it unplugged, the car does start but stalls. with it plugged, car just cranks without turning over after the symptoms have shown again.

[pinkpandaslide]

pulled the fuel pump today and confirmed it is a walbro. also, i installed and left a fuel pressure gauge on the car to help diagnose. same issue. but this time i can look at the fuel pressure when the car dies and wont start back up. it was at 15-20 psi!!!! when the problem happens. I unplugged CTS and it fires right up but stalls. It does it everytime. Tried about 5 times and then I checked on the gauge and its at 0 psi! Could this mean the fuel pump heats up and dies? Time for a new pump? I'm getting close

[ojkush]

did the new fuel pump fix the prob? i have the rb25 s14 swap and my fuel pump fuse keeps blowing if i do a hard pull.
im running a walbro 255 thats 3 months old.

[fliprayzin240sx]

If you're fuel pump fuse keeps popping, time to add a relay switch for your fuel pump. If that doesnt fix it, I'd look into a new pump. Walbro aren't exactly the most dependable pumps out there and to make worst, there are bootlegs out there now.

[IDP FTW]

pulled the fuel pump today and confirmed it is a walbro. also, i installed and left a fuel pressure gauge on the car to help diagnose. same issue. but this time i can look at the fuel pressure when the car dies and wont start back up. it was at 15-20 psi!!!! when the problem happens. I unplugged CTS and it fires right up but stalls. It does it everytime. Tried about 5 times and then I checked on the gauge and its at 0 psi! Could this mean the fuel pump heats up and dies? Time for a new pump? I'm getting close

Bump. I'm having a very similar issue. Car just cranks and cranks, sometimes starts (runs rough) but dies when you touch the throttle with the CTS plugged in. Unplug the CTS and the car will start right up, able to apply throttle and sounds great. Replaced CTS with no change. Help!

S1 Rb25 in S13
Wiring specialties harness:bs:

[jedi03]

could have gotten a defective one....but on the walbro subject, walbro suggests buy directly from them or an authorized dealer as there are ALOT of counterfeits that don't hold up the same and are identical to where walbro couldn't even tell it was an off brand...