rb20 help, yes, i searched.

[oneeyedRALPHY]

just picked up an s13 about a week ago or so with an rb20 and i got super ripped off. used to live in pennsylvania and needed a car to drive down to florida because i was moving. saw it on craigslist, checked it out.

i don't really know shit about rb motors, as the previous S13 i had was all stock. the guy told me it needed a bit of work but it would get down here. a little bit of work turned out to be a bit of a bitch.

got new coils for it (red devils), new alternator, alternator fuse, and re did some wiring because it looked like a 5 year old did it. now, the car runs amazing. sometimes.

the first time i turn it on that day, it takes about 4-6 tries to turn on but once it's running i have no problems. when i start driving it after the first turn on, it lags and bucks horribly for about 5 minutes then smooths out. now from that point, it goes one of two ways. it will run beautifully all day, but my clutch will slip. all. day. or it will start misfiring about 10-15 minutes after, but my clutch will be perfectly fine.

i know the clutch probably doesn't have anything to do with it, at all, but i want to solve that issue as well. now, when it misfires, it still runs, but it sounds like an sti, and has almost no power compared to when it's running good.

does anyone have ANY clue as to where to start with this?

here's the setup:
rb20
fmic 3" piping
i think there MAY be an rb25 turbo on it but not sure, i just know that stock turbos push 11lbs~ (?) and my boost gauge is showing a boost peak of 19 psi, constant 16~17
and apparently a Spec Racing stage I clutch

any info would be greatly appreciated,
thanks guys.

[Sileighty_85]

If it is a stock turbo you should not be boosting it past 13 PSI or that turbo will be destroyed, Which Im quiet surprised it hasn't yet

Check ECU for Codes, Could be CTS or MAFS

[Jtuned_andy]

start with the simple stuff. clean and scuff all your engine grounds make sure their tight, something could be jangling around making weird things happen.

check timing at your CAS

clean your mafs with appropriate cleaner from autozone or whatever

check your plugs for deposits

check for boost leaks and vacuum leaks

17-19 psi is WAY out of wack and that turbo will blow if you keep running it on those numbers.

[oneeyedRALPHY]

About the turbo... I figured it should have blown as well. I drove it for a couple of days before the drive down south, and I drove it all the way down til I hit south carolina and my alternator took a dump. A drive that long with little pulls here and there to distract my boredom, it should have blown up.
Actually now that I think about it, I probably should have mentioned that as well... I'm running a ka24e alternator. Right out of the box, if that has anything to do with it.

As for checking ecu codes, I don't think my cel works, the only thing that works on my cluster is gas gauge and the little warning lamps for seatbelts, etc, unless there is a light on the ecu?

As for mafs, I just bought a new one last week which helped greatly (yes, it was worse). Its a j30 MAF, according to most search results, they're a direct usdm replacement?

And to be quite honest, I'm not sure what a cts is?

Also this guy I worked with, when I chaged the coils and maf sensor, he hit the CAS with a socket really hard and it cleared it up a bit, but I dunno if that's good or bad. Seeing as I feel like you really shouldn't be hitting sensors and such with a hard metallic object, I'm gonna go with bad?

Thanks for not being an ass about it.

[Sileighty_85]

J30 MAF only works with the Series 2 RB25's

RB20's use a Green Tag J60 MAFS

The ECU should have a LED light on the ECU.

CTS= Coolant Temp Sensor If it goes bad the car will run really shitty

[oneeyedRALPHY]

I'm not quite sure how to check thetiming at the cas, ill google it quick unless its not too crazy and you dnt mind typing it out, haha.

I know there's a realy small leak coming from the boost gauge tubing, and I just got new couplers for the intercooler, just in case as well.

I just put new plugs in last week, so I don't know if you would be able to check them yet?
The old plugs I couldn't get a true reading from because 4 out of the six coils were bad.

I know I should have been a bit smarter than buying a shoddy ass pre swapped car but I needed something bad and after my first 240 I don't know if ill ever buy anything else again, and there really wasn't much else. As for the grounds, I'm gonna do that tomorrow. It just sucks cause the guy who did the swap was like 18 so there's random wires and whatnot everywhere. Smh.

[oneeyedRALPHY]

That's what it is, I'm sorry I meant j60. It's a green label. Sorry about that. Ill check the coolant temp sensor as well... I read that you can replace it with a z33 oem? Just in case.

I'm getting to the point of just rebuilding the whole car myself.
Any thoughts on the clutch issue? I should probably just get a new clutch, huh?

[oneeyedRALPHY]

I'm going to see if I can check the ecu really quick, I'm on my phone so I will keep you guys posted.

[Sileighty_85]

Only a J60 MAFS will work with the Stock ECU, Z32's are not a Direct replacement.

Spec is Garbage get an Exedy or ACT clutch

[oneeyedRALPHY]

I have a j60 mafs, the j30 wasthe old one in it, I got them mixed up.
And as for the cts if its bad I have to order an rb20 specific replacement online?
No usdm replacement?

And I've been hearing really bad things about spec...
I was actually looking at exedy clutches, but I need something daily driveable if need be and I heard exedy wasn't the best choice for that, but then again that's just peoples opinions. I'm quite open minded so feel free to throw in your two cents about them, haha.

[Sileighty_85]

According to FAST its RB20 Specific.

If it is bad the P/N is 22630-01U00- This is a J-Spec Nissan Dealership P/N, May not work at a USDM Dealership

I myself have a Exedy Stage 1 clutch in my RB25, Hold up fine and DD able, My wife has no problem as well

[oneeyedRALPHY]

Thanks for the info and P/N.

If you don't mind me asking, what specific model clutch are you using?

Checked the ecu and the only codeit throws is 43 and the site I just checked states that as a trottle position circuit?

[oneeyedRALPHY]

Throttle*

Sorry I'm on my phone.

[Sileighty_85]

Thanks for the info and P/N.

If you don't mind me asking, what specific model clutch are you using?

Checked the ecu and the only codeit throws is 43 and the site I just checked states that as a trottle position circuit?

Not sure on the clutch P/N but I'm using a 300ZX clutch disk and plate.

Yeah the TPS would def cause those issues


P/N for that is 22620-02U00 if yours is Originally a MT.

If you wanna order these parts go over to www.Nissanparts.cc and give Russell a call, he can order these parts for you

[oneeyedRALPHY]

The rb was originally automatic... I'm going to guess its a different P/N, huh?
Let me search quick and see what I find, I appreciate the help. This has been driving me crazy forever.

One more question, and I promise I'm done, haha...
If there's no boost controller, how do I set my boost back down?

[Sileighty_85]

AT P/N is 22620-02U10

Connect a Vac Line directly to the Waste Gate. It should lower it to like 4-6 PSI

[tanman_s13]

on my old rb, my ignitor was starting to fail and also i had a couple bad coil packs. the wiring harness on mine was pretty brittle so even moving it wrong would cause it to misfire

[benarovi]

is it a blue hatch that you bought?

[oneeyedRALPHY]

No, its a flat red hatch, I bought it in PA.
I feel like there might be something up with the ignitor too cause it kind of just rests on the top of the motor all that's holding it from falling it out of the car is a random wire.

Do any of you know if there's a usdm part replacement for the tps?

[Kingtal0n]

The joy of owning an RB20 is not in the performance wholly, but rather, in the situation you describe. Your job as the owner of that vehicle is to restore as much of the original components from the OEM RB20 configuration as possible, and you should be using the most low mileage components you can find.

The owner of that vehicle that successfully drives it every single day should have:

Spare sensors sitting on a shelf, such as MAF/CAS/CTS/TPS/ECUetc...

The owner's toolbox should be overflowing with replacement OEM electronics to keep her going and to eliminate electronics as a source of issues, because there will always be issues as mileage increases.

The owner has a wideband because he knows that the proper A/F ratio is ultimate importance, as one major source of incidental damage to those engines is related to piston-ring failure, which would require removal of the engine and replacement, which will be very hard to accomplish based solely on rarity and mileage of leftover components no longer being made by any factory.

The owner has the OEM turbocharger set to it's minimum boost, no more than 7psi, because he knows that the fun of driving that engine is in the engine itself, not it's performance aspects. Nobody uses an RB20 for performance SOLELY, it is the prestigous nature of an inline 6-cylinder engine properly running in your daily driver 240sx that is impressive and nostalgic. Drive that car like an antique, give people a chance to notice it.

He always uses 93 octane of course, take every preventative measure you can. Overcool it, I dont care if the temps seem rock solid on the dash, get a real coolant temperature gauge and have someone weld the aluminum fitting for it into the actual coolant outlet, make ducting and add high quality electric fans and a real Griffon radiator, since whatever is done already is non-oem as it sits, I would always recommend the OEM mechanical fan, but that is not an option on your limited space.

regularly do compression checks and leakdown tests, write the numbers down (COLD and HOT) and compare them months apart for a general update.
notice trends in your odd situations, like the one you mentioned about the clutch. You are right in saying that a clutch should not slip based on running "right or wrong" but a clutch would slip when the engine is making more torque, as it might when it runs on all cylinders. If it sounds "like a subaru" then it sounds to me like a cylinder is not firing(intermittenly), and with the proceedure and accessibility of those rare electronics I mentioned you would be able to just swap parts and narrow it down right away.

I am sure it is a blast to drive and I want you to drive it forever, watch the oil and keep the oil clean, even if that means every 2000 miles oil changes, turbocharged engines tend to wear the oil faster than other engines, and keeping the oil visibly clean will keep the turbocharger happier. Oil is the life of all engines, and also all turbochargers. Watch the temps and use only distilled water and green generic coolant. If there is currently any tap water in the engine you need to do a proper flush, or at least fill it with distilled water and completely empty it a few times to wash out all the tap water (like you would a bottle)

[oneeyedRALPHY]

I agree with you kingtal0n, 100%. My plans were to restore almost everything to as OEM as possible, but as with almost every build, I'm in a bit of a jam.

As I previously stated, I recently just moved from PA. I have no home as of yet, and the car that I was using to look at possible home purchases needs a TPS. I literally have a backpack and like 3 small boxes of clothing, and I still manage to have a few extra sensors plugs and parts.

I just need some way to fix it until next week when I move into a house.
It runs, but she's my baby and I don't want her running bad.

[Kingtal0n]

the first time i turn it on that day, it takes about 4-6 tries to turn on but once it's running i have no problems. when i start driving it after the first turn on, it lags and bucks horribly for about 5 minutes then smooths out. now from that point, it goes one of two ways. it will run beautifully all day, but my clutch will slip. all. day. or it will start misfiring about 10-15 minutes after, but my clutch will be perfectly fine.

i know the clutch probably doesn't have anything to do with it, at all, but i want to solve that issue as well. now, when it misfires, it still runs, but it sounds like an sti, and has almost no power compared to when it's running good.

does anyone have ANY clue as to where to start with this?

here's the setup:
rb20
fmic 3" piping
i think there MAY be an rb25 turbo on it but not sure, i just know that stock turbos push 11lbs~ (?) and my boost gauge is showing a boost peak of 19 psi, constant 16~17
and apparently a Spec Racing stage I clutch

any info would be greatly appreciated,
thanks guys.

Your situation is inspiring, keep those sensors by your pillow to sleep better.
First your starting issue. It could be the "start signal" at the ECU is not receiving a signal when you turn the key to start position. I have seen this cause a start delay. Also, the ECU itself could be bad, I have seen some ECU's cause start delay (verified by changing the ECU and having the problem dissapear). Fuel pressure could also cause the problem, perhaps you are turning the key and the rails are dry, so you are cranking the engine but there is no fuel in the rails yet for a few seconds. Try priming the fuel system or looking at a fuel pressure gauge before and during cranking to verify.
So far we discussed start signal, fuel pressure, ecu as starting related issues. The engine may require 6 cylinder events before it syncs it's cam angle sensor so see if you can count 6 compression events right before it fires up, and if so, that is likely what you are experiencing. In that case I will recommend a stronger battery, located by the front of the vehicle. If your battery is small, old, or located in the rear, it may seem like you have starting issues because the voltage will be low and starting performance will suffer.

Now, On to the next symptom. I believe you have a boost leak, build a boost leak check device (using home depot parts) and fill the plumbing to 16+ psi and listen for it hissing. A leak right after the maf (in the air filter hose) should also be inspected for, as it would also cause the problem you describe. This is where MAF sensors and ECU spares would come in handy. Also the Coolant temp sensor and TPS sensor are known to cause this sort of issue. and even the knock sensor can have an affect during WOT on performance.
I would START with the boost leak check, lower the boost, followed by verified ignition timing by Factory proceedure, new spark plugs, a wideband gauge, at that point you should know if a replacement maf sensor it necessary or if the issue is spark related. the boost leak check will kick everything off and it may end right there, otherwise the wideband will reveal issues such as maf/cts/tps and the new plugs/verified timing/lower boost will reveal
everything else. Get a wideband regardless, for the price and importance you almost cannot afford not to own one these days.

Reduce the boost to its minimum setting. 19psi is far too much especially for OEM injectors and an OEM turbocharger from any RB series engine. Oh, she will run, as you have mentioned, she runs PERFECT right? well she will run perfect even with 16.7:1 air fuel ratios, gradually eating up the insides of the combustion chambers and deck. Yeah that engine will take the abuse- for a while. But then when it lets go, the block and head may be trash. And I will tell you exactly what is going to happen: a piston ring is going to fail. You will notice because oil will suddenly be burning off the exhaust manifold one day under boost. A compression check will yield low compression on one or even two cylinders. Before you even THINK of turning the boost past 7psi, you need larger injectors, a stand-alone computer, a tuner that knows what he is doing, a real fuel pump, an EGT gauge/Wideband gauge, and a sprinkle of good fortune.

[Kingtal0n]

I was also thinking to mention to check the ground on the ignition coil wiring at the back of the head, and that a bad or hot igniter could be at fault, or even the wiring itself from the coilpacks into the wiring harness of course. It is all connected together, and as these things get old, sometimes even a bit of resistance in the wires along with the magnetic field interference from other nearby wires and the buildup of resistance at the tip of the spark plugs along with the eroding gap as plugs acquire mileage- all of this resistance is prevention of the delivery of spark, which of course would lead to a misfire as described. If we could, we would change everything from the spark plug back, at the very least, swap plugs.

[oneeyedRALPHY]

Thank you, a lot. This is greatly appreciated. Since being in FL I've changed the spark plugs, got a new coil harness, and I'm about to be on my third alternator. I checked the ecu last night and it gave me a code 43 throttle position circuit.

Now for the ignitor, I'm a bit worried about that as well... its literally sitting on top of the valve cover. Like I said, this is my first rb so I'm not too sure where its supposed to go?

I'm gonna put the boost down, and keep searching for a tps for now. I have no clue where to get a new ignitor from, so I'm not too sure what to do about that.

[oneeyedRALPHY]

It seems like all the vacuum lines are connected... there's two coming out of the intake manifold, one is plugged and the other one goes to the boost gauge. I have no clue where they go?

[Chrisbarlow891]

wow this sounds like my car when i first got it, s13 coupe with rb20, it always would either pull really hard or lag like mf. so i finnaly got around to checking it all out, i took my tps off and checked that out, put a nismo fpr on, and then replaced my maf, that will make it run like shit, then come to find out it needed to be remapped, when i got that done it ran soo good, but after about a month i blew the stock turbo, my rpm doesnt work and my speedo/ hud is always flickering on and off, will never stay on? but all the red warning lights work fine, i find that strange, anyone know what i could do to get the rpm and lights in dash to work?? also i put a rb25 turbo and its not tuned, whats the easiest way to upgrade computer to tune!?

[drifteddaily]

OK!!! Same car as one eyed ralphy. well same engine weve now put in an s-13 coupe. Ralphys back in pa and im trying to get this finished as a welcome home present. since the last time hes postd... we swapped the rb-20 from the hatch to the coupe. weve raped the old shell and its in the drveway. we bought a clean shell( another hatch ) and ordered an rb 25 along with every other part nissan makes even down to the roll cage. but im gonna save that project for when he gets back. Im even newer to this than ralphy is so forgive me for my lack of knowlwdge. I am learning and im learning fast. the county wants the cars working and tagged in fifteen days so i haent been sleeping to well. doing a lot of research on these motors and recently been to my first drift competition. I see why people love these cars... ive been inspired... just not the best timing lol. Anyways... im Mike. ive been trying to get this coupe started and through talking to people i think its the CAS. i turned it on and turned the Cas by hand and did not here clicking.. i heard the zzz noises and the fuel being pumped but no click cick. we went to auto zone and got a replacement but it was for a 300 zx. same test.. same thing. keep in mind his is the same engine that ralphy was cursed with from pa. all the same electrical problems seem to exist and now this one. looking at the harness... i know as an electrician that wires can short in the wierdest of places and this harnes just looks beat to death... a lot of connectors are fitting really loosly and wires are all brittle. in fact, the CAS harness fell apart in our hands as we took it off. Im thinking with my lack of knowledge of trouble shooting machines such as these. I should just get a new harness to rule out all the bs shorts and broken wires etc??? Im opened for any knowlege any one can throw at me. Ralphy is a good guy and off the no bs... I owe him a ten second car... long story but i have the opportunity just lackin some know how lol. thanks for reading and in advance for any responces... see you on the track.

[Yellow4g63]

Drifteddaily I would just get a new harness and start fresh. Who knows what the guy before Ralphy did. Also I can't remember for sure but the 2 green relays near the ecu control injector and coils for power I think. Did you change the timing belt, tensioner, idler and water pump on the motor?

[drifteddaily]

hey thanks for the reply. been crazy the last few days. i felt i was running out of time so i made the call to straighten up and maybe wait for ralphy. i was able to successfully fit the engine through a sttandard door way lol. i have been reading as much as i can on rb 20s and 25s in anticipation for his return. im a visual learner i guess and theres too mny questions i run into that im sue are stupid ones but some time stupid questions arise and some body usually says hey.. that was a dumb a** question etc... besides its not my car and hes gonna need it to be perfect for his standards im sure you can attest to that statement. as for your suggestions. they all seem like good places to start trouble shooting that i really didnt know to look. i think ill take another shot at it when the new harness gets here and go from there. hoping thats it... i wanna hear her scream so bad. thanks again for your help. as im learning these skylines and 240s, im also learning to use this site and seems really informative and most of you import guys are usually wiling to spread helpful knowlege. kinda like an underground fam almost. really starting to learn what its all about...anyways... ill keep you posted as the weeks go on. seriously wanna be out on the track this summer.