s14 RB20DET revving problems??

[3v1Ls14]

yes have searched on google and all sorts of Nissan forums

..and yes i know its a problematic RB

Here's how it is..

Starts ok and idles ok, has had slight miss and stopped firing one cylinder, new plugs and fixed the miss.

It will idle fine and rev ok, but wont rev past certain rpm almost like a fuel cut. try driving it and soon as its about to boost it chuffs black smoke and loses power, but doesnt die.

fuel pressure is good, 40psi at idle or just under. have tried known good maf, known good ecu. injectors all working well and have specified impedance. I have continuity tested every wire in the loom from ecu plug and checked for accidental earthing out in ALL wires.

tried unplugging tps, same result, o2 sensor, same result, afm, same result, idle valve, same result, temp sensor, same result.

i am getting ecu code 55 so no fault. new plugs, good afm, good ecu, new temp sensor, standard turbo, good fuel pressure.

no matter what i unplug the conditions of how it is running do not change.
even if i unplug afm and try rev doesnt die or anything. just revs up a bit then hits the cut EVERY SINGLE TIME. getting very frustrated and running out of ideas. dirty fuel? air leak? any ideas or suggestions would help. cheers guys

[budderigs]

Sounds like wrong maf. Or wiring issue going to the maf. Which maf are you using. The rev cut is a typical maf related issue on rb's

[3v1Ls14]

iv tried 2 mafs. was running previously sat for a while and now having this prob.

maf has been rewired twice brand new wires and sheilded wire. plug changed with a mint one as well. soldered and heat shrinked etc

ran fine before just since i have put the turbo on its doing this. turbo had almost no play at all, a mint turbo basically.

mafs used r both j60 green sticker series 2 rb20 rounded plug type

[budderigs]

Check for plumbing leaks between turbo and intake manifold. Maf to turbo. Bypass valve and crankcase vent.
Just about any intake leak will cause an issue.

On mine I had the same issue. Found that I wired the maf plug looking at it backwards. Switched the wires around and it fixed the issue. Then when I swapped to my Greddy turbo it did it again when I missed the bypass valve.

[3v1Ls14]

i have changed loom and new ecu as old ecu blew when afm shorted out. new loom and ecu now wont start, 42psi fuel pressure when it primes, has spark, almost fires but doesnt, makes dull popping from exhaust pipe but just wont bang properly.. any ideas?

[budderigs]

what does it do with the maf unpluged now. if the maf is unplugged, the computer will ignor most of the other sensors and do its best to idle. so try unplugging it. and see if it starts?

what model number computeer did you install now? its not as commen on rb20 computer as it is for 25's but some of the computers are pinned differrent. s1 or s2 rb20s have different pinout's as wel/l as different sensor outputs and different intake manifolds. is your 20 a redtop or gray

[3v1Ls14]

maf unplugged doesnt start either. i put more gas in, checked plugs they were fouled up so i cleaned them all and tried again, same result, dull popping during cranking. ecu showing 55

i installed ecu 23710 04U11
i last had in an 04U12 i know the codes are both rb20det r32 a/t ecus so no reason why it would be different

silvertop motor as well.

i have checked injectors by turning cas and all 6 are operating and i am getting spark as well, good fuel pressure, ecu is turning on properly etc

pretty confused and stuck at moment

[budderigs]

timing off? do you have a timing light to check it? if it is popping through the exhuast the timing would be late. try turning the cas counter clockwise to the max. and see what happens. if it hard cranks back the timing a little. if it starts make sure you get a timing light on it asap and set timing at idle to 20

[3v1Ls14]

all timing marks line up properly on cams and crank pulley. i have had it set in middle both sides and almost everywhere in between, same with the tps.

just pops a lil bit of black smoke when it does pop, not wet spluttery black smoke though more like sooty kind of smoke..

all 6 injectors clicking, plugs firing. injector plugs are on the correct injectors as with coil plugs.

does same thing with idle unplugged, afm unplugged, o2 unplugged

[budderigs]

Plug everything back in. Turn the cas all the way to the left(counter clockwise) then try to start it. Feather the gas pedal a little and see if it starts. It now sounds like your ignition timing is off. The computer probably has a different curve programed in it.

[3v1Ls14]

factory unmolested ecu from a factory rb20det gtst skyline r32. i have tried feathering gas with cas at fully counter clock and also fully clock wise. ive tried WOT and no throttle and partial throttle and tapping throttle. the ECU was previously running a 30DET (poorly) but dont see how that would change ecu's inner workings.

the small puff of black smoke makes me think it is fuel related..?

[3v1Ls14]

also the pop got louder today, almost sounded like a back fire but not enough heat to ignite it for it to be a proper full on back fire just a loud pop and small black chuff

[budderigs]

Also get a dvom and set your tps too .4-.5 volts. You have to narrow down the problems not make more.

[budderigs]

Do you have a 3"to 2.5" coupler laying around?

[3v1Ls14]

i have silicone a one yeah

[budderigs]

i have silicone a one yeah

Cool might need that.

Can you get the compressor housing cover off your turbo? Check and make sure it didn't lock up? Also check it for play.

[budderigs]

Also pull off your down pipe in case the exhaust is plugged.

[3v1Ls14]

i will try both next time i can work on it and see if any change

[budderigs]

I am starting to think this is getting over thought try the simple stuff. Maybe recheck your plugs and do a compression check just to make sure.

[Nidd]

Are you lining up the half moons on the cas and cam when you reinstall the cas? If they aren't lined up it'll run funky or not at all.

What RPM does it cut out at? If it's going into limp mode and stopping at 2500 it could be maf related.

Also check the ignitor to make sure it's still good. Had some miss problems with my rb's and switched to z32 and seems to work better now. Easy swap to do.

[3v1Ls14]

not running at all now. wont fire. i pulled ecu out and opened it up, was told it was a standard gtst r32 ecu when i bought it. i notice it has mec r109 on the top cover. on the side it says mec r127. inside its actually neither, its chipped. so probably chipped for something completely different. have a standard one now that i borrowed from a work mate. i will try that in the next couple days and see what happend.

my cas is keyed into the cam gear so it can only go in one way

[preston240sx]

sounds like a maf problem ... seems the ecu is telling the injectors to flood it .... my rb20 hard starts alot and wont start ,,,ill unplugg the maf it will fire right up plug it right in andthe car will run fine ... i still get the 55 code lol

[3v1Ls14]

doesnt fire with maf plugged in or unplugged and ive tried another maf as well

[3v1Ls14]

update: i got it started the other night, i pulled cas out, and the half moon key from the cam was STUCK IN THE CAS. i never knew it was broken when i got the motor i just assumed i must have slipped cas back in perfectly every time. so i lined it up at tdc and saw where it was broken on cam and lines the cas up opposite to that and put it in. fired first time.

i have now got it running and everything, but if i blip the throttle to maybe 1/4 it will rev out and hold the revs there on its own for a little bit, and has a horrible miss when i drive it, but only off boost. as soon as it hits boost it pulls hard and stops missing, drives normal ON boost but shit OFF boost. any ideas as to where to start looking? i have seen many people problems ON boost but not off where as im having opposite problem

any help would be good if any one has had similar problem