RB25 starts fine then sputters and dies HELP!

[240Lover770]

ive been dealing with this for about 2 or 3 weeks now and im out of ideas. it drove fine for a week when i got it with a slight stutter problem under acceleration. then i filled up one saturday and that night i was driving from a meet and it started sputtering really bad. hitting the accelerator did nothing but made it sputter worse then the engine died. pulled over to see if i could see anything wrong and nothing. went to start it and everything seemed fine. drove it for a few then it started sputtering when i gave it gas. wouldnt let me go past 1000 rpms. got it to a store parking lot and let it sit. started it up again and everything seemed fine. tried to drive down the street and it wouldnt rev and i have no power as it was sputtering. then it shut off again. at this point i got it towed home. got it in the garage and started it up. starts fine but wont let me rev it. after 2minutes its starts to sputter and cough and you can see the afr gauge go from 14.7 to 16.00 then to nothing and thats when the car dies. as time went on it got worse to the point where it sounds like its missing now.

its basically an all stock engine with stock ecu. only mods are q45 throttle body,front mount,BOV deleted, freddy intake and fuel pump. nothing else.

things that ive changed:
ecu-same problem
fuelpump-same problem
fuel pressure regulator-same problem
fuel filter-same problem
spark plugs-same problem
maf-same problem

i also thought it might be bad gas, so i completely drained the tank and put fresh gas in. SAME THING. it starts runs like nothing is wrong,then 2 minutes into idle it starts to cough sputter and run lean until it kills its self and turns off.

im out of ideas. the only things i havent changed is the o2 sensor,TPS,CAS,knock sensor, iacv, coil packs, and injectors. i have a set of injectors coming in and im soon to buy another set of coil packs. if that doesnt solve it i dont know what the hell to do.

can any RB series 2 experts please help. its a later model rb that uses neo coil packs,cas, and iacv. im unsure if its actually a neo being that i have side feed injectors.


i dont know how to upload videos here but if you facebook me i can send them to you there. all help is welcomed.

[RB25GUY]

well the q45 throttle body and no recirc bov will make the car run like shit if its not tuned! but tps could be the culprit but lets see after the injs and coils

[usmcgetsome]

Q45 MAF usually intended for aftermarket ecu and tune. Check wiring connection to that maf. Check the wiring to your fuel pump tank assembly (mine was brittle and kept shearing). When a maf begins to fail youll notice at normal operating temps the engine will just die randomly. It'll cool down for a bit and then start right back up and drive till it gets hot again and repeat.

[wiring specialties]

Q45 MAF usually intended for aftermarket ecu and tune. Check wiring connection to that maf. Check the wiring to your fuel pump tank assembly (mine was brittle and kept shearing). When a maf begins to fail youll notice at normal operating temps the engine will just die randomly. It'll cool down for a bit and then start right back up and drive till it gets hot again and repeat.


If the engine is struggling to start when warm, a common failure is the temp sensor. Easy thing to try. Its the 2-pin one.
If you need a new connector, just hit us up.

[240Lover770]

it ran fine without a bov for the whole time i had it until now. and i have a regular e60 maf.

[240Lover770]

If the engine is struggling to start when warm, a common failure is the temp sensor. Easy thing to try. Its the 2-pin one.
If you need a new connector, just hit us up.

the engine barely runs long enough to get warm

[240Lover770]

well the q45 throttle body and no recirc bov will make the car run like shit if its not tuned! but tps could be the culprit but lets see after the injs and coils

injectors will be here next week. i still need to find a set of coil packs to buy. the throttle body and no bov didnt seem to have an affect on anything when i first got it. ran really good. then one day it just shit. only thing i noticed was slight hesitation on acceleration. thats about it. i never fifured out why because now the car wont run normally

[240Lover770]

yesterday i pulled the old plugs and did notice they were wet. put in new plugs and it sounded like it was missing or not running on all cylinders. its like its degraded over time somehow

[dbeiler]

So instead of testing anything, you intend to just dump a bunch of money into buying unnecessary parts? Buy a multimeter and do some proper diagnosing.

My guess is a faulty CAS or ECT.

Take that thing to a real mechanic before wasting your life savings on unneeded parts. Any half-decent modern day technician should have the issue diagnosed in little time.

[240Lover770]

So instead of testing anything, you intend to just dump a bunch of money into buying unnecessary parts? Buy a multimeter and do some proper diagnosing.

My guess is a faulty CAS or ECT.

Take that thing to a real mechanic before wasting your life savings on unneeded parts. Any half-decent modern day technician should have the issue diagnosed in little time.
i have a miltimeter sir. if i had the time to sit and play electrician i would. read out fuel pump wires and tps. seem to be fine. havent read out the maf yet. and like i said it doesnt stay on long enough to properly check whats going on.

[240Lover770]

So instead of testing anything, you intend to just dump a bunch of money into buying unnecessary parts? Buy a multimeter and do some proper diagnosing.

My guess is a faulty CAS or ECT.

Take that thing to a real mechanic before wasting your life savings on unneeded parts. Any half-decent modern day technician should have the issue diagnosed in little time.

also what is ECT?

[240Lover770]

may just throw in the towel and bring it to a shop

[240Lover770]

Bump. Does anyone have anymore useful pointers

[wiring specialties]

After re-reading you post I agree with dbeiler about the CAS or ECT.

[240Lover770]

After re-reading you post I agree with dbeiler about the CAS or ECT.

Thanks. This is my first RB. I usually deal with SRs. But it caught me off guard. I have a temp sensor on the way. And I found a decently priced CAS. Will let everyone know what happens here in a few days. Thanks for not beating me up too bad.

[projects14zenki]

I had a similar issue, ended up having a boost leak. Check your Intercooler piping clamps and couplers, also check your intake for a vacuum leak like the hose going to the brake booster. But if all checks out maybe be your cas.

[240Lover770]

I had a similar issue, ended up having a boost leak. Check your Intercooler piping clamps and couplers, also check your intake for a vacuum leak like the hose going to the brake booster. But if all checks out maybe be your cas.

Thanks. I've checked for vacuum leaks as well. May take another look.

[240Lover770]

So far not the coolant temp sensor. I'm done for the night. Will work on it more towards the weekend

[240Lover770]

Disappointing update if anyone cares. Changed injectors and coil packs. Still nothing. So I folded and got a crank angle sensor. Yes I'm throwing parts at it right now because I simply don't have time to sit and read wires as I'm always on the go. Flame if you want but it is what it is. Thanks in advance

[240Lover770]

No one is really responding but I'm just gonna use this thread as a place holder. Checked voltage at coil packs and all are reading between 11.4 and 11.6 if I remember exactly. Adjusted tps .44v. Tried to start and it let out a backfire. CAS is on order but didn't read it out yet. I also am going to check to see if I have codes once consult arrives. Injectors are getting proper voltage as well.

[Tyler_240]

if you unplug the MAF does it start? Have you triple checked for vacuum/boost leaks?

I would double check your ECU harness connector is tightened down good. Dont over torque the bolt, but make sure its gudentight.

Triple check your grounds. I am unsure if the coilpacks on a RB are the same, but remember the SR has that head to firewall ground and the back of your freddy should have 2 ground wires attached to it.

Perseverance my friend.

[240Lover770]

if you unplug the MAF does it start? Have you triple checked for vacuum/boost leaks?

I would double check your ECU harness connector is tightened down good. Dont over torque the bolt, but make sure its gudentight.

Triple check your grounds. I am unsure if the coilpacks on a RB are the same, but remember the SR has that head to firewall ground and the back of your freddy should have 2 ground wires attached to it.

Perseverance my friend.

I unplugged the maf a week or 2 ago and it makes the car die as soon as it's unplugged. I've checked the grounds that I can see and all are secure. I'll check again for the hell of it. Thanks for responding

[wiring specialties]

did you ever get a chance to pressure test?

[240Lover770]

did you ever get a chance to pressure test?

As in cylinders? Or fuel pressure?

[240Lover770]

I messed around with the CAS today just for the hell of it until my new one comes. I can hear the injectors fire but no buzz from the coil packs. I don't know how loud the buzz is supposed to be but I put my ear right up to it. I've changed the coil packs multiple times. And it did USED to run. Now it doesn't wanna start. For the most part still trouble shooting. Parts will be here Tuesday

[projects14zenki]

If you want to check to see if your getting spark and fuel try this out. get a noid light set to see if your getting a injector signal remove the coil pack install a spark plug hold it to the valve cover. crank the engine and see if your getting a signal. Do it for all cylinders. That will take care of ECM signals of that checks out check fuel pressure and lastly check engine compression.

[240Lover770]

Got consult in today. For whatever reason that program doesn't work. Downloaded Ecu talk and it works. Ecu isn't throwing any codes. The new CAS came in as well. But I have not installed it yet. Pretty much stuck right now.

[240Lover770]

To whom ever is comes upon the thread. IT WAS THE CAS. the cause will cause all these issues making you think it could be something else. Took out the CAS and it was worn out. Bought a remanufactured one and it fired right up. Now this thread will be here and it actually has an outcome.

[MR_GUTTI]

I'm glad you fixed it! Good job!

[RB25GUY]

To whom ever is comes upon the thread. IT WAS THE CAS. the cause will cause all these issues making you think it could be something else. Took out the CAS and it was worn out. Bought a remanufactured one and it fired right up. Now this thread will be here and it actually has an outcome.

YAY now enjoy it!!!

[SoundEfx]

Glad you found the fix AND posted it so that others can benefit.

[240Lover770]

Glad you found the fix AND posted it so that others can benefit.

Thanks. That's why I kept updating even though I wasn't getting any response. Every post I looked at while I was doing research had no results or outcome or real answers to the problem.