rb25 hesitation issue. please help

[thisisnotphil1]

alright i need some help with my rb in my s13. anyone with any sort of automotive knowledge please feel free to chime in. so basically the car acts completely normal in neutral. it revs fine all the way to redline, no missing, sputtering, smoking. honestly it sounds great. when im driving its a completely different story. so what happens is, i ease into first gear, and theres no issue. when i get into second gear, and put an actual load on the motor, somwhere between 3-4 thousand rpms, the car bogs, hesitates, feels and sounds just like a fuel cut. every once in a while i can put my foot down and power through it basically. but not very often. its happens right around half throttle if i had to guess. sometimes its so bad the car doesnt even accelerate. the problem isnt gear specific. happens in every gear but it behaves differently every time i drive it. so far ive adjusted the fuel pressure thinking that maybe i was running to rich or to lean. not it. ive cleaned the maf sensor. ive changed the tps, all my vacuum lines are correct. its not the spark plugs and i dont believe its the coils because if doesnt ever feel like its miss firing. ive searched around and have stumbled upon people who have a similar problem but what they have done hasnt worked in my situation. the only mods i have are a fmic, walboro 255, aeromotive afpr, and i have the wiring specialties rb harness for an s13. im at a loss. i feel like it possibly could be the maf sensor because of how it randomly decides to act like a fuel cut issue. but im confused that when i ease onto the throttle i can get a halfway decent pull. heres a video of the pull. it doesnt hesitate until around 55 seconds but i get off of the gas and i dont have another video where the car does it. next week ill show you guys what its actually doing. but thanks for the help in advance guys. i really appreciate it.

Rb25 pull - YouTube (http://youtu.be/1WjiBsTSZLI)

[fliprayzin240sx]

Start off by making sure your TPS is set properly and your base timing is good.

[thisisnotphil1]

ok. ill double check

[thisisnotphil1]

checked everything. no change

[2.5T_/<ouki]

What is your fuel pressure set to?
Fuel pump could be going out.
Check to make sure your spark plugs are gapped properly (.028 - .030).
Try swapping the ignitor. 300zx ignitor works just fine.

I had a problem just like this and it turned out to be my MAF. What had happened was the solder points inside the MAF were loose. I had to resolder and everything was fine. I also had to fix my spark plug gap.

[thisisnotphil1]

fuel pressure is set to 42psi with no vacuum. the pump is fine its brand new. im just guna buy new plugs just to be safe. i never knew one problem could be related to so many things. ive seen people say its the coils, its the plugs, its the maf, its the tps, its a boost leak, its the ecu. its annoying haha

[kouki-gymkhana]

Sounds like a boost leak. Check all the intercooler piping for holes, couplers for loose clamps, and/or build a boost leak tester and report back. I had a very similar problem and it turned out to be a loose coupler.

[2.5T_/<ouki]

Yup! Process of elimination. I would try the cheapest first (Boost leak/Plug gaps).

[thisisnotphil1]

yeah def cheapest first haha thanks guys for the input. much appreciated. ill keep you updated on what i try and what, if anything, works

[Sileighty_85]

Get a tuned ECU as well. Stock RB25 ECU's are garbage.

[2.5T_/<ouki]

Get a tuned ECU as well. Stock RB25 ECU's are garbage.

Straight up! Read my NIStune vs. stock ECU thread lol.

[thisisnotphil1]

Yeah I was thinking about going aem after my kidney sells on Craigslist.

[twofouroh]

Happened on mine when we test drove the first time boost leak and gap your plugs

[PrimeDirective]

I think you are over boosting for the stock ecu. What is the boost set at? Stock wastegate actuator and no boost controller? Depending on where you have your boost source for your waste gate actuator you could be getting large boost spikes which would cause the ecu to cut fuel. If you are on a stock ecu I don't really think you can go above 8psi.

I originally had a long line from my greddy intake manifold to the wastegate actuator. I would floor it at like 3.5k rpm in any gear I would get boost spikes up to like 11 or 12 psi and hit fuel cuts well before the red line. Basically the turbo will make 12 psi before the boost pressure had time to make its way through a long line to the wastegate actuator. I had to tap a hole in the turbo discharge and ran a short 3-4" line from there to the wastegate actuator.

This makes sense why you can sometimes power through it because if you go slower the wastegate actuator can keep up and keep the boost at normal levels.

I would bet money that over boosting is your problem.

[thisisnotphil1]

Everything is completely stock. No boost controller. I didn't think the ecu could even monitor the boost because there's no map sensor and I don't have the stock rb25 boost solenoid. There's no reason the ecu would even know to cut the fuel based on boost. Am I right?

[PrimeDirective]

Read what I said. This applies to the stock wastegate actuator, regardless if you have a boost controller or not, I do not have a boost controller either. The ECU may not be able to tell its at 12 psi but it does know its getting a lot more air than it should through the MAF, that is why everyone says that the stock ecu is a piece of shit, because it does dumb ass things when you turn up the boost.

Describe to me where the boost source is going to the wastegate actuator. Also hook up a boost gauge when you do a run and tell me what it says, I'll bet you are seeing boost higher than the stock 7psi.

[Jez]

Had this on my R32, closed up the plug gap and problem solved.

[Sileighty_85]

Read what I said. This applies to the stock wastegate actuator, regardless if you have a boost controller or not, I do not have a boost controller either. The ECU may not be able to tell its at 12 psi but it does know its getting a lot more air than it should through the MAF, that is why everyone says that the stock ecu is a piece of shit, because it does dumb ass things when you turn up the boost.


Youp, when the ECU senses more boost (Air Flow) then factory It will pull timing and dump fuel to prevent detonation.

Mine did it when I swapped in my Hyper Gear Turbo, even though I was only running about .7 bar it felt slower. Put the stock turbo back on and it it felt "better"

[thisisnotphil1]

Read what I said. This applies to the stock wastegate actuator, regardless if you have a boost controller or not, I do not have a boost controller either. The ECU may not be able to tell its at 12 psi but it does know its getting a lot more air than it should through the MAF, that is why everyone says that the stock ecu is a piece of shit, because it does dumb ass things when you turn up the boost.

Describe to me where the boost source is going to the wastegate actuator. Also hook up a boost gauge when you do a run and tell me what it says, I'll bet you are seeing boost higher than the stock 7psi.

ohhhh i understand now. that makes a lot of sense. i apologize for the noobish behavior haha. this is a crazy learning experience. im actually going to school for auto. but anyway im running the boost source from the hose that comes off the back of the cross over pipe that has the bov on it. i dont have a picture of it. the car is actually at school so when i have class im going to put in new plugs and gap them correctly and see what happens. now if i am having over boost issues what should i do?

[2.5T_/<ouki]

You are def not having over boost problems. I'm almost positive if you're not using the stock boost selenoid you're only pushing 5psi maybe 7psi. Also, make sure that the actuator is on its own boost source, don't T it to anything else. My hot pipe (intercooler pipe on turbo side) has a nipple on it; I run a 4-5" hose from my actuator to the nipple.

Gap the plugs correctly ;).

[PrimeDirective]

You are def not having over boost problems. I'm almost positive if you're not using the stock boost selenoid you're only pushing 5psi maybe 7psi. Also, make sure that the actuator is on its own boost source, don't T it to anything else. My hot pipe (intercooler pipe on turbo side) has a nipple on it; I run a 4-5" hose from my actuator to the nipple.

Gap the plugs correctly ;).

I don't think you understand how a boost solenoid or the waste gate actuator works. WITHOUT the boost solenoid he can ONLY be running 7psi, no more, no less that is what the actuator is set at.

You can see boost spikes if the tubing going to the actuator is too long or has a T in it.

thisisnotphil1 if the new spark plugs don't work then you should use a boost source for the actuator that is on the hotside of the intercooler and make it as direct and short as possible. From your description it sounds like your boost source tube is on the cold side of the intercooler you could definitely be having a boost spike problem. With it sourced on the cold side the air has to travel a long ways before it gets back to the wastegate actuator, and by the time it gets there the turbo could already be making more than 7psi.

Having a boost gauge will tell you if you actually are a having boost spiking problem at all before you start messing with everything.

[thisisnotphil1]

Thanks a lot primedirective I extremely appreciate the help. I will try all these things when I'm at school. The source I'm using for boost basically as far as you can get from the actuator. Pretty much on the same pipe as the bov. I'm hoping this is the issue just because of how easy it is. Plus I'm broke haha

[2.5T_/<ouki]

Any luck with this?

[thisisnotphil1]

Ill be at school tonight so I'm guna try and get everything going running properly. Ill keep you guys update.

[smoked240]

Good info here. Rb's can be very picky man! Have you just tried starting it and unplugging the maf to see if that changes anything?

[thisisnotphil1]

No i havent tried that but we rulled out the maf sensor tonight. Just wanted to keep you guys updated. Didnt get a chance to get the car into school tonight. Worked on it a little outside but it was dark. Tomorrow night im getting it in and guna fix the issues. Thanks again for all the help! Stay tuned for more updates

[thisisnotphil1]

the pump is fine its brand new. im just guna buy new plugs just to be safe.http://www.odauto.com/song9-4.jpghttp://www.dutvs.info/a121.jpghttp://www.odauto.com/15.jpghttp://www.odauto.com/16.jpghttp://www.odauto.com/17.jpg

.....What?

[PrimeDirective]

Its a spam bot..

[FutureFab]

Ya it posted in my thread too.

[thisisnotphil1]

Alright so tonight i moved the hose for the wastegate from the cold side piping to the hot side and my problem still exists. After much debate from friends in class and my teacher, i think the next best thing to try a new maf sensor. It is 100% not the spark plugs, coil packs, and there are no boost leaks. I took my teacher out on a test drive for the first time with him in the car and after i moved the wastegate hose did the same exact thing but i got the car to power through the hesitation and it pulled like it should. I only got it to pull once though. The first thing he said after it happened again he said "its def not a boost problem" and then said "it almost feels like a maf problem." We tried to pull the maf off while the car was running but it wouldnt stay running. Has anyone had maf sensor problems that sound like this? I havent ever had experience with a maf going bad.

[thisisnotphil1]

The only other thing i can think of is that theres something going on with the tps.

[2.5T_/<ouki]

Gap your plugs correctly! I'm pretty sure I stated the size earlier but try .028-.030
Usually if you unplug your MAF and the car dies then its not a MAF problem, I could be wrong tho. Have you take a multimeter to the MAF to make sure you're getting correct voltage? How about to the TPS?

I had this problem before. Went with the 300zx TT AC Delco plugs @ the gape ruined above and never had a hesitation issue since.

[thisisnotphil1]

The gaps are all perfect. Ive checked them 3 times already. Do you know what the voltage should be for maf and tps? Ill do some research

[2.5T_/<ouki]

The gaps are all perfect. Ive checked them 3 times already. Do you know what the voltage should be for maf and tps? Ill do some research

Here are my results. Pretty sure I stated it there.

http://zilvia.net/f/tech-talk/475116-bad-tps-rb25.html

[thisisnotphil1]

im at school right now im going to check the voltage for the sensors

[thisisnotphil1]

Alright zilvia heads. Heres an update. Got a lot of things figured out tonight. The first thing i did when i got into class was go straight to the crazy snapon obd code reader that we have and checked to see if it had the nissan connector for the consult plug. To my surprise it was actually there. So after the computer was all hooked up, i turn on the car, and i start reading every sensor and they were all working fine maf, tps, injectors, rpm, o2, everything. I keep reading and as i get farther down i see the o2 sensor is reading LEAN. WTF?! So we 1000% made sure the o2 sensor was good with the voltage, and everything matched up. Now i say to myself how the hell can i be running lean when i have the fuel pump and everything is running correctly and at the right psi? I dont mean to drag on but my mind was blown tonight. So i go into the fuel mixture tab on the scanner but i didnt touch anything. I wanted to see what the car was doing before we started messing around with the ratios. (btw if anyone has this scanner i envy you. Its fucking dope) Take the car for a quick drive, let it get up to normal operating temp and i step on the gas. Except NO HESITATION! WTF AGAIN! It was being kinda sluggish but not hesitating and was still running lean. So i turn around, and add fuel to the ratio with the scanner, let it load(again, FUCKING DOPE) i get on the gas, pulls HARD in first, HARD in second, and then gets lean again in third but it was crazy. It was the best the car has ever run in my possesion. Now heres where i need some more help. What could be causing the car to run so lean? I dont understand why the afr is so off. Another question i have is, is it possible that just by plugging in the scanner, could the ecu be running on like a base timing map where it wouldnt hesitate while its plugged in, and my issue is actually a timing issue? Im soooooooo close. I hope one of you guys can help

[PrimeDirective]

Hey man, sorry I was wrong about the over boosting. I would do a google search on lean rb25 as there are A LOT of posts about it. Good luck!

[thisisnotphil1]

Hey man its alright. Trial and error. At least now the wastegate will be opening quicker lol

[thisisnotphil1]

I would do a google search on lean rb25 as there are A LOT of posts about it. Good luck!

There are so many reasons why it could be running lean. To be honest, i think its the pos rb25 ecu thats the issue. I dont understand why after i plug in the scan tool the car doesnt hesitate at all. Just runs slow. So frustrating. :hahano:

[PrimeDirective]

Yeah that's true.

Try checking the fuel pressure. Some of those posts suggest if the fuel pressure is too high it can cause the engine to run lean, though I can't explain why. RB fuel pressure should be at 35-36 psi at idle with the vacuum line off and the engine warm.

[thisisnotphil1]

The fuel pressure is good. The pump and filter are both brand new. I have it set between 36-37 psi at idle with vacuum off. I think its an issue with the ecu telling the injectors to pump an insufficient amount of fuel. Only because the maf sensor and the tps are functioning properly and i can change the injector duties with the scanner to run correctly.

[2.5T_/<ouki]

Yeah possibly the ECU however I thought the poppy rb25 ECU makes the engine run rich. Are your knock sensors plugged in?

[thisisnotphil1]

Yeah possibly the ECU however I thought the poppy rb25 ECU makes the engine run rich. Are your knock sensors plugged in?

Indeed they are fine sir. :rawk:

[707silvia]

Try disconnecting the tps and drive the car and see if it still lags. I'm having the same issue.

[401imports]

i had the same issue with mine. i had a 25 s2 few things were wrong, tps was out of wack. when u turn your key to the on position, listen for the fuel pump to prime, does it sound a lil weak? i hard wired my fuel pump and the car ran 200 times better. when u hard wire it it gives alot more power to the pump and before i had it hardwired it wasnt getting alot of power and it wasnt dumping enough fuel. so that fixed one of the problems. i also messed with my tps sensor and cas sensor. cas sensor was a big issue, you touch that thing and it changes the car like crazy. even if your fuel pump is running good without it hardwired, you should do it anyway. give that a try if you havent

[thisisnotphil1]

Fuel pump and tps are both fine. I've checked them probably ten times now. I'm now leaning towards either a bad ground somewhere or it's the ecu.

[thisisnotphil1]

just wanted to keep you guys updated because i hate when threads die and no problems are ever solved. tonight im going through the harness and making sure everything is grounded correctly. i noticed that on my alternator theres is a ground that should be on the block and not on the actual alternator itself. probably not the problem but im moving it anyway. i also discovered in another post that the ecu is tuned on a different octane level in japan so im going to go buy some octane booster and see if that does anything. i guess its worth a shot haha.

[Matt191]

Uhm my two cents, but I had an SR doing this and it turned out to be a bad alternator just check the voltage coming off the alternator. It should be fine but you never know, damn gremlins....

[thisisnotphil1]

Alright. Ill check that out tonight. I just want this thing to run right. So damn frustrating

[Matt191]

I know how you feel fought with my SR for a month and changed the alternator and bam changed the alternator and she ran good. But sadly she isn't running again....-.-

[thisisnotphil1]

Alright just got home from school and I finally have figured out as to why the car has been hesitating. It's a bad COIL PACK. So I appalogize to every person who said it was the coils. Tonight on the LAST ride around the block, the coil finally shit the bed completely. Miss firing like a mofo. Sounds like a Subaru. Picking up 2 coil packs tomorrow. Thank you everyone for the help. You don't know how appreciative I am. Will post back tomorrow to confirm.

[2.5T_/<ouki]

Awesome! Glad you found the problem man. Did you get the new coils? How's it working out?

[thisisnotphil1]

I just found out tonight that it was one of the coils. Hopefully tomorrow ill be able to pick one or two up. I'm super broke right now haha

[smoked240]

Don't worry about the octane. Japan uses a different octane rating system so it's actually tuned for 92-94 octane. Good deal finding out the problem! Might as well replace the bad one and plan to replace them all soon! After I get my car to the dyno, I'm going to be swapping my coils for spitfire or LS. Also I would look into a tune. The Rb ecu blows and it is holding your engine back.

[Driftwire]

CONGRATS on getting to the source. Little trial and Error and your all set. Probably had some arcing or burning on the coil pack under load

[[email protected]]

check to see if you have the gasket/spacers between the cam angle sensor and exhaust camshaft. if not you need a new exhaust cam and sensor because that gasket/spacer keeps the sensor shaft from binding in the exhaust cam and wearing away at the teeth causing poor running and messed up timing

[[email protected]]

i didnt see the last post..lol

[thisisnotphil1]

Don't worry about the octane. Japan uses a different octane rating system so it's actually tuned for 92-94 octane. Good deal finding out the problem! Might as well replace the bad one and plan to replace them all soon! After I get my car to the dyno, I'm going to be swapping my coils for spitfire or LS. Also I would look into a tune. The Rb ecu blows and it is holding your engine back.

Haha thanks man. I'm def looking into doing the ls coils. I'm waiting to find out about a job so if I get it, first thing I think I'm buying is a power fc. Tonight I'm going to find out which coil it is. I wish it was a spark plug issue just because they're easier to find. Is anyone close to central jersey that would like to donate a good coil pack? Lol I have like 40 bucks to my name. I can't seem to find any coils anywhere. Well no one has answered me yet on any other forums. I think I'm going to stop at a shop close to me and see if they have one laying around. Thanks again guys for the help. Can't thank everyone enough :bow:

[2.5T_/<ouki]

Haha thanks man. I'm def looking into doing the ls coils. I'm waiting to find out about a job so if I get it, first thing I think I'm buying is a power fc. Tonight I'm going to find out which coil it is. I wish it was a spark plug issue just because they're easier to find. Is anyone close to central jersey that would like to donate a good coil pack? Lol I have like 40 bucks to my name. I can't seem to find any coils anywhere. Well no one has answered me yet on any other forums. I think I'm going to stop at a shop close to me and see if they have one laying around. Thanks again guys for the help. Can't thank everyone enough :bow:

Do you plan on keeping the engine stock? PFC is overkill for a stock engine. You'll pay $800-$1000 just for the unit and another $600-700 for a tune. You should definitely look into NIStune for your setup.

[thisisnotphil1]

No I'm not planning on it staying stock. Which is why I want to go with the power fc. I would like to make 350-375whp with the motor I have now. My problem is, I'm not 100% sure as to what I want to use the car for haha I figure my power goals just for right now aren't crazy and with that power ill have a fun street car. When I get out of school I'm most likely going to build another motor and just go all out. I have to do some more research on both of them and see what they have to offer. I looked into the power fc a little but know nothing about NIStune. I honestly haven't even thought this far in advance because of the problems I was having haha

[thisisnotphil1]

alright guys. as soon as i got to school pulled the coil packs out, and just as i suspected. burn marks on the plastic where it was arcing. i was unable to get any coil packs before class, so to get it to stop arcing, just for the time being, i put some silicone on both sides just to insulate it better........i honestly cannot wait to do the ls coil pack upgrade. the car runs 10,000 times better. the first time i took it around the parking lot, i wasnt getting my hopes up just incase it wasnt the coils. put my foot down coming out of the turn into the parking lot. SIDEWAYS! almost shit my pants. first time i was ever sideways in a 240. fucking addicting. thank you guys so much.

i apologize for the shitty iphone videos but, heres the before video...

Rb25 hesitation - YouTube (http://www.youtube.com/watch?v=eDO6RqDFvLI)

and heres after we fixed it...

Rb25 test drive - YouTube (http://www.youtube.com/watch?v=nOQQD3shu4M)

i honestly couldnt help myself laughing like a little girl. fucking crazy.

[2.5T_/<ouki]

I just sold my ls2 truck coils I was going to do on my RB. I was hurting for money so had to let them go :(