HELP! RB25 is running like shit!

[burninskulls0911]

so i put an rb25 in my car and ,ive been having issues with it ever since..
when i drive it calm it runs fine, idles good, everything seems perfect..
then when i drive it hard it starts to break up and lose power around 5k and wont rev past 5500..

there are no boost leaks
timing is set correct
spark plugs are bkr7e gaped to .028
it has a walbro
and a new z32 fuel filter

im about to clean the iacv because im out of ideas

the motor is an all stock rb25 with a FMIC and a freddy manifold

[voodoo_child]

did you replace the fuel pump? my cousin is runnin a rb25 as well. we replace the fuel pump for the same problem bogs down at high rpm and runs crappy. we use the stock rb25 fuel pump (JECS). bigger than his old WALBRO. sad to say the car isnt running good again the car dies, we have to unplugg the cam sensor connector and connect it back in and it would start right up. if you replaced the fuel pump try checking your MAF sensor.

[burninskulls0911]

i put a new z32 fuel filter in and it has a walbro..
im going to take it out and see what the filter on the bottom of it looks like.. thanks for reminding me

[b00stinbmx]

its not a fuel problem bro. double check your spark plugs, and tape up the coils, look for any cracks its either grounding out, or a spark plug is cracked or not gapped right. i GUARANTEE you its a ignition problem. i had the same exact shit happen to me a few times with my rb.

[burninskulls0911]

its not a fuel problem bro. double check your spark plugs, and tape up the coils, look for any cracks its either grounding out, or a spark plug is cracked or not gapped right. i GUARANTEE you its a ignition problem. i had the same exact shit happen to me a few times with my rb.
well ive tried two different sets of spark plugs and ive gaped them about three times.. what do you mean by tape up the coils?

[Couped_up'd]

My rb20 did this. Do you know that one set of coils is good?

My rb20 ended up being a crack in the valve cover to valve cover hose. Ran fine idle/barly on it. I would get on it and it does what yours is doing. The turbo would suck air threw the cracked line...which you fallow that line it goes right after the maf, and before the turbo.

Hope that makes some sence.

[burninskulls0911]

My rb20 did this. Do you know that one set of coils is good?

My rb20 ended up being a crack in the valve cover to valve cover hose. Ran fine idle/barly on it. I would get on it and it does what yours is doing. The turbo would suck air threw the cracked line...which you fallow that line it goes right after the maf, and before the turbo.

Hope that makes some sence.
hmm thats interesting..
i have a catch can and i was noticing that one of the lines didnt have a clamp on it.. maybe im having the same issue as you were..
ill check it tomorrow

thanks!

[secondtonone317]

did you even get this issue resolved?

[Triperformance]

Do the obvious checks as well, check for vaccum leaks!

[Katsumbhong]

MAF Sensor

[Triperformance]

MAF Sensor

^ What he said lol. Also when you orgionally check for Vaccum leaks how did you do that procedure? Visual checks for Vaccum leaks doesnt always work.

[g35gabby]

it sounds like you have a Vac leak only in boost as the increase in pressure causes the crack to open and show itself. this could also be caused by a vac line/coupler that isnt completely sealed(seems to be a very common mistake with the mazda speed guys).

[greenzenki86]

maf or ignition for sure, dont drive it hard, will just lead to bigger problems

[greenzenki86]

holy shit this is old, man i feel like an idiot....... :(

[s!lv!a]

I know this is an old dead thread but I'm having these same issues with my rb25 and I've been told it just needed an adjustable fpr but I want a second opinion.

Here's my setup:

Stock series 2 rb25
Isis intake manifold
Q45 t/b (adjusted to correct voltage)
New Super spark coil packs
New bkr6-e plugs
Z32 fuel filter
Hks ssqv
Fmic
Walbro 255


Problems:
Crappy idle
Bogging/stuttering in high rpms ~5000
runs too lean at idle and too rich at WOT
Doesn't bog in lower rpms even at full boost


What I've tried:
Cleaning old plugs (helped somewhat for about 2 pulls then went back to running bad)
Put in new plugs (ran slightly better than old plugs)
Cleaned maf (ran like shit for almost a week)
Adjusted idle screw (helped idle slightly but still ran bad)
Checked coil packs
Checked for vacuum leaks
Checked for boost leaks


It'll run fine for driving around and even at wot in low rpms but at high rpms it sucks and if I try to start it after the engine is already warm it won't idle unless I hold it at idle with the throttle but if I drive around the block it'll idle fine. And it'll also idle fine if I cold start it but it idles high on cold start and stays high until I shut it off and restart it when it's warm. I've removed the cold start thing on the q45 t/b and don't even run coolant lines through the t/b.

Any help or suggestions?

[Sileighty_85]

check the codes on the ECU, might be a bad Coolant Temp sensor

[gsn0526]

i had the same problem....mine was the fpr. i could tap on my stock one and it would run better for one good pull then it would break up again. i went with the nismo which bolts on perfectly.

[s!lv!a]

Coolant temp sensor might make sense.. I was actually just under the hood and bumped my coolant temp sensor and tb sensor wiring and idle fluctuated lower so I wiggled the wires and somewhere it's crapping out because when I wiggle the wires idle drops. I don't think that's an answer to all my problems but it's a start at least..

[redline racer510]

updates????

[s!lv!a]

Got the car to idle now by cleaning out the AAC but even after adjustment it idles a little high now but that's better than not idling at all like it was doing before.. I should have a fpr in the next couple weeks so hopefully that solves the rest of my problems..

[redline racer510]

does it still break up at high rpm?

[s!lv!a]

Yep, just as bad if not worse..

[Sileighty_85]

so you still havent pulled codes or checked the CTS?

[s!lv!a]

^^^ No, not yet. It's kinda pointless to try searching for more problems right now when I know for a fact that it won't run right without an adjustable fpr either way.. Once I change that out, then we'll see how it runs and start tinkering with more stuff. I'm supposed to be getting my z32 rear calipers sold in the next couple days and then purchase a nismo fpr..

[Sileighty_85]

Regardless those issues need to fixed (if any), its best to find out everything that wrong so you can make a plan and do research on fixing the issues. Ignoring them wont fix it.


mine runs just fine with the Stock FPR, I plan on upgrading it, but i DD mine everyday and boost it without any problems

So your issue is probably gonna be electrical

Nismo FPR are garbage, get a Tomei or Sard

[redline racer510]

Regardless those issues need to fixed (if any), its best to find out everything that wrong so you can make a plan and do research on fixing the issues. Ignoring them wont fix it.


mine runs just fine with the Stock FPR, I plan on upgrading it, but i DD mine everyday and boost it without any problems

So your issue is probably gonna be electrical

Nismo FPR are garbage, get a Tomei or Sard
I second the nismo fpr, friend had one and it never ran normal until he switched it out for a aeromotive. Ultimately you need to figure out whats wrong and the fpr isn't sounding like whats causing your issues. You first need to check for codes and see whats coming up. The fpr should be the least of your worries at this point.

[s!lv!a]

^^^ maybe nobody on here knows this, but it's a VERY common problem for series 2 rb25's to run rich with stock fpr and a walbro due to the fact that the stock regulator can't bleed off the excess fuel fast enough so it tries to force all the extra pressure through your injectors not only causing it to run rich, but also causing it to miss because the plugs will easily foul out running pig rich all the time and even get blown out by too much fuel. And if someone wants to buy me a new fuel rail or adapter so I can run a sard or aeromotive, be my guest but until then I'm sticking with nismo because it fits on the stock rail and it WILL help fix some if not all of my issues. And what's the point in checking everything I've already checked other than pulling the codes when after getting an adjustable fpr, I'm going to have to make adjustments all over again to those same things. I haven't ignored any problems, I've already sorted most out if you read all my posts and this isn't my first car, I've built several cars and I've owned four different s14's so this isn't my first rodeo by any means. I appreciate the help, but telling me to check things I've already checked isn't helping much.. (other than pulling codes, although I even did that a while back and fixed the issues then)

The only thing electrical that could be malfunctioning is the q45 tps and I say that because with the stock manifold, stock tb and stock fuel pump, everything ran fine. Since then the fuel pump has been upgraded, the coil packs have been changed to super spark coil packs, the manifold has been changed and I'm now running a q45 tb. And yes I've checked the tps for correct voltage and everything is as it should be. The only issue is that I think either the tps might have a short or the wiring might be faulty because sometimes I can wiggle the wires and it causes idle to fluctuate. I know the connection to the tps is good because I cleaned it and soldered it so like I said either tps or the wiring has become bad. My option now after checking my wiring again is to either buy a new q45 tps or buy an adapter to put my stock rb tb on the new manifold which also means new piping and couplers on my cold side due to the difference in tb size.

And for the record, mine too is my daily and I still daily it no problem as it is. Only in boost in higher rpms do I have any troubles and my car runs so rich its off the meter. Under WOT after say 4k rpms my AEM uego just reads 10.0 flat and won't go further simply because it can't read it so rich.. If I ease into it I can probably redline the car as long as I'm not under boost or WOT but that would be pointless and I don't drive my car that hard anyways..

[Sileighty_85]

I dont know why the S2 FPR has issue when used with the walbro when its the same as the S1 as well as a few other RB's.

From what I've read you cannot use the Q45 TPS on the S2
The Greddy instructions mention when installing the Q45 TB that after Jan 1995 RB's (S2) you need some kind of Sensor coupler for the TPS.

[MADE]

Im not an expert but having had a S1 and currently now I NEO RB I dont see or have I ever had or known anyone who has had the Stock FPR problem. When you get around to changing it let us know if it works. I vote on ignition or elecrical.

[s!lv!a]

I dont know why the S2 FPR has issue when used with the walbro when its the same as the S1 as well as a few other RB's.

From what I've read you cannot use the Q45 TPS on the S2
The Greddy instructions mention when installing the Q45 TB that after Jan 1995 RB's (S2) you need some kind of Sensor coupler for the TPS.

I believe that's just because the plugs themselves are different and won't connect directly and thats why you'd need a coupler. Mine however is hard wired in and to my knowledge is wired correctly. I'll look into the tb stuff further just to make sure.

[!Zar!]

Didn't read if anyone suggested this or not, but check your ignitors. Check them out for corrosion on the contact where the spring touches the inside of the coilpack. Also make sure the spring is touching the spark plug properly.

[s!lv!a]

^^^ my super spark coilpacks are less than 4k miles old.. Lol, they don't have any rust or corrosion at all anywhere but thanks for the advice..

[s!lv!a]

Alright so I worked on the car some today, I checked the cts and everything checks out there.. I added a new ground to the harness/engine and it made a noticeable difference, not huge, but noticeable.. I then tried tapping on the fpr with a socket wrench some since someone mentioned that their car would run better for a couple pulls then go back to running rich.. Well tapping on the fpr made way more of a difference than I was expecting, it ran MUCH better for 3 pulls and then I parked it before I got the cops called on me lol.. It was still breaking up in the high rpms but not nearly as bad and not as early either but I've been watching my afr's closely and noticed that the afr progressively gets more and more rich as soon as I floor it which to me means that the regulator isn't bleeding off like it should and it's building up more and more pressure as my foot stays on the gas and to me that more or less confirms some of my previous theories about needing a new fpr. And I've also been reading that the series 2 rb25 ecu is known for flat spots and running rich so I'm thinking an safc2 would help a bit too until I can get a standalone and since I was already considering that anyways, I may go for it sooner if the fpr helps substantially. Then once I work out the gremlins I'm swapping to an rb20 actuator so I can run 10psi :D

[redline racer510]

Get a new fpr and see if it runs better, an safc is just a band-aid IMHO.

[s!lv!a]

^^^ yeah but that's all I'm needing for now, easier to spend $100-$150 on a used safc while I'm still tweaking things vs. spending over a grand on a good standalone when I don't necessarily need that just yet..

[redline racer510]

I thought you were trying to use the safc to fix your rich afr.

[s!lv!a]

Well I'm hoping the fpr more or less eliminates the running rich problem and then I can fine tune those flat spots out and keep it from running rich with an safc. I plan to run 10psi on the stock turbo via rb20 wastegate actuator once I get all the little stuff sorted out but I don't plan on buying a standalone until I upgrade the turbo and injectors. An safc2 or neo should be perfect for just the minor tuning I'll need since the motor is basically stock.. I adjusted timing slightly today and my car feels about the best it ever has but it's still running damn rich. I seriously can't wait to get this issue dealt with because I've still yet to feel the real potential of this motor!!

[MADE]

If you keep adding stuff how will you know if you fixed the problem or just masked it?

[s!lv!a]

If you keep adding stuff how will you know if you fixed the problem or just masked it?

What do you mean? The problem only happened after adding a walbro and swapping the intake manifold.. The only thing I plan on adding is a new fpr and a safc and considering the fpr is the solution in theory, that would be solving the problem, not masking it.. The safc is just to make minor adjustments and clean up flat spots that the stock rb ecu is known for.. If you read my post thoroughly, I have no intentions of adding more boost, turbo, injectors or really anything else until I get the problem fully resolved..

[s!lv!a]

Ok so I installed the nismo fpr and it made another big noticeable difference but still running rich right about 5k rpms. It pulls much harder now after installing the fpr and I've adjusted it to ~36-37psi at idle with vacuum and ~43psi w/o vacuum (iirc). I think I still have an issue with either the tps wiring or the tps itself. Hopefully it's a wiring issue and not a tps issue because then I have to decide whether to buy a new q45 tps or buy an adapter plate for the stock rb tb and sensor.. Any other suggestions at this point?

[s!lv!a]

Alright so I finally got around to making a boost leak tester and omg... Apparently after the last time I took off my AAC valve to clean it, somehow the gasket got messed up and I didn't notice it but there was a pretty massive leak there and after fixing that leak, I also found a couple pinhole leaks in the welds of my i/c piping.. That was only with 2lbs of pressure... I have to go get my compressor from storage but I should be able to see soon how bad the boost leaks are, I'm going to test the pipes at 12psi (since I'm only running stock boost that should be more than enough) but even after fixing just that one bad gasket the change is huge. The car pulls even harder now and I'm loving it more and more. I have all these little gremlins but the car seems to be waking up more and more and I'm really beginning to love my rb even after all the hell I've been through to get it running right and still being in the process..

[redline racer510]

What I would do is remove your intercooler piping and buy these rubber pipe plugs one for each side of the pipe and adapt a pneumatic quick connect with a small gauge and test each one to 10-15 psi and spray down the pipe with soap water. If there are any leaks you will immediately see them, then just have some one weld up the holes for you and repeat.

[s!lv!a]

^^^ that's a good idea, that's why it's exactly what I did.. Haha, I used a PVC cap and a tire valve though and I'm just using my boost gauge to read pressure since that's what I'm relying on for proper boost anyways.. And I'm pressure testing the whole system all at once instead of each individual pipe that way it tests the pipes, the i/c, the intake, and all the couplers all at once.. I just use a coupler on my turbo inlet with the pressure tester and I can test everything without disturbing anywhere that holds pressure.. Lol, but yeah I do plan to make sure I have no leaks up to about 12psi but I already know where two pinholes are in the welds with only 2psi that I have to get taken care of before putting even more pressure in the pipes. I should have those welded up this week and then search for more with more pressure and some soapy water.. Even though really I can hear every time there is the smallest of leaks lol, even those pinholes were pretty loud..

[s!lv!a]

Alright, been a little while since I updated, I fixed about 80% of my boost leaks, still need to get one sorted out at my #1 injector and I think I should be in the clear. Also apparently you guys were right, my cts must have been going out because it finally took a shit on me yesterday and my car would barely even run. After swapping that out with a brand new KA cts my car is running MUCH better. However it still runs rich, just not nearly as bad which I think may just be due to my timing still being off (haven't had a chance to buy a light and check it). I've also read that the KA cts reads a little off from the rb's, anyone out there able to support this claim?

[Luvs2slide]

Ever able to get this sucker running like a champ? Anyword on the CTS KA issue vs. the RB CTS?