My Rb is SLOW!! help me fix it

[lilskyline240]

Ok first ill give you a little background on my car. its a 90 coupe that i bought last summer with what was thought to be a bad KA in it. the motor had no power over 4000rpm. Kinda fell on its face. So i bought a new KA24 and swaped it in and turboed it at the same time. This motor STILL had the same problem of no power over 4000rpm. Just falls on its face! So i figure its something with the engine harness or ecu or something so i decide to go with an RB.

so all last winter i did an Rb30 project and finally got it swapped in my car about 2 months ago and running. now this is what pisses me off!! the car has NO POWER OVER 4000RPM!!! im gettin soooo pissed and im bought to just sell this thing and get a Trans AM.

heres a list of what ive all checked:Pressure tested to 20psi for leaksNismo fuel pressure regulator set at 37psi at idle with VacA/F ratio is at 11.7:1 at WOTTiming is right on 15* with TPS disconnectedNew plugs gapped at .028Car idles and drives fine with no weird noisesno miss-firing, back-firing of any kindcompression is 175psi on every cylinderturbo is brand new rebuilt Australian 300zx turbo (slightly larger than rb25)boost holds steady at 7psiVac at 20mm/hg at idlenew Fuel filterwalbro fuel pump

I have run out of things to check. It seems like the problem has to do with my Chassis and not my motor. What could be causing my problem??? the only 2 possible things i can come up with is Grounds or Fuel pump/tank

Firstly my gas tank has some big dents in the underside from the guy before me and a drifting accident but i dont think that could be causing my problem since my Fuel pressure is perfect throughout the RPM range. going up with boost and holding

Second possibility would be my Grounding. I relocated my battery to my trunk when i swaped out my first KA last summer. I have the battery grounded to my trunk and also a 2 gauge wire running from the negative battery terminal to my block. Without this wire the car wouldnt start at all. Then i have a wire coming from the firewall to the head, and one from the frame to the intake manifold. i figure this is enough grounds but i could be wrong.

Please help me fix this problem so i can enjoy the RB like ive been waitin to for the last 8 months..

[240z4u]

Hey man, after I get moved next month you should drive it over here and I can help you figure out whats wrong.

Do you have a wideband or anything installed for diagnosis?

[lilskyline240]

yes my wideband is installed which is how i got the reading of 11.7:1 for my A/F ratio at WOT. Im bout ready to put this thing for sale on craigslist.

how hard would it be for u to put ur Power FC in my car to see if anything weird comes up

[240z4u]

Power FC installation is easy. Problem is all of the cables are run through the interior so I would have to take my console out etc...

We could do that as a last resort though.

Are you sure your cam timing is perfect?

Evan

BTW, I know I have been emailing you but lets keep it on the board. It may be helpful to someone else.

[lilskyline240]

yeah cam timing is dead on. checked that 5 times now.

sounds good to keep it on the board so someone else can search this

do you think grounds could be causing this? cuz it didnt start until i ran that ground from my trunk to my block

[240z4u]

I have to say, I am surprised the car wouldn't start until you ran that ground. You do have a grounding strap between the block and a good clean chassis ground right?

Sounds to me like there is knock and its pulling timing (or something is rattling and its pulling timing).

Did you try driving with the knock sensors unplugged like we talked about?

Evan

[S14-NEO]

well if you want my opinion, id try and get yourself another MAF..just curious are you using the same MAF as you did in your turbo KA...is it a Z32 MAF?...not that that would matter at all..but if you used it on one engine that wasnt working and then you threw it onto another engine setup and was still havin the same issue ..just a thought....MAF can do the exact thing your describing...it can read voltage but it may not be able to read flow....i (just had a maxima in the shop today) with a problem just like the one you are having..you can crank it right up just fine but , it will make no power even in park past 4000 rpm's...

[Yellow4g63]

Sounds like something with in the car? maybe fuel lines are clogged? or fuel filter, clogged cat? what stayed the same when you did all your swaps?

[lilskyline240]

when i unplugged the knock sensors the problem got worse and ran like crap. About the engine ground, i did think it was weird that it wouldnt start unless i had a wire running from the batt to the block. Maybe my ground from the chassis to intake mani isnt good.

im using the stock rb25 s2 maf so i doubt thats the problem. although i could try to swap it out for another one to see what happens.

the only things the same between both swaps would be all the fuel lines, gas tank, fuel pump and grounds. Everything else is new. No cat just a test pipe. New fuel filter (z32). I was thinking it had to do with the fuel system but if i had a clog somewhere wouldnt it show in my fuel pressure or my A/F Ratio?

[Yellow4g63]

The fuel psi would be funky if there was a clog do you have a gauge on your FPR? Did u check the ecu for any codes?

[lilskyline240]

i have a Fuel pressure gauge and it reads a solid 37psi while idling and goes up to about 47psi and holds steady when boosting. So i doubt the problem is there. But who knows, im open to any suggestions

Im going to try to run my codes this weekend. Since its a s2 ecu i dont have the lights to check the codes off of so i hope i wired in my CEL so i can run my codes.

Im going to try my spare ecu also this weekend to see if that changes anything

[Joe]

do a fuel pump volume test.

run the fuel pump for 30 seconds, have the output go into a 2l bottle. measure how much is in there.

if its half full, your pump is putting out 120lph.

etc etc

[lilskyline240]

if im running a walbro 255 wouldnt it be doing 255lph? so essentially fill the 2 liter bottle in 30 seconds? And how do i go about gettin the fuel pump to run for 30 seconds without stoping?

[bmadd2402]

just jump the fuel pump relay.

[lilskyline240]

well i drove the car today with the rear knock sensor off and it didnt seem to make a difference. so i think either the wiring to the knock sensor is wrong or the sensor is fried maybe. Not sure tho
Modified by lilskyline240 at 11:19 PM 5/24/2008

[lilskyline240]

is there anyone around the Milwaukee WI area that has a spare rb25 MAF i can try out? Isnt it the same maf as a maxima?

[ItzGenX]

do a fuel pump volume test.

run the fuel pump for 30 seconds, have the output go into a 2l bottle. measure how much is in there.

if its half full, your pump is putting out 120lph.

etc etc

Well I wouldn't say just any ol' 2 liter bottle.. It may melt .

[lilskyline240]

anyone else with imput?

[lilskyline240]

Ok new update. I was going through my wiring again and checking things over and i had a problem where when i had a brown wire hooked up on the 8 pin brown plug in the front pass side of engine bay it would blow the engine control fuse. This was with my old ECU so i tried connecting it again today and it blew the engine control fuse right away again but the car still ran exactly the same. So i wonder if this has to do with my problem?

What on the chassis of the car does the engine control fuse go to?

[S14-NEO]

which pin location is this brown wire in the brown connector

[ItzGenX]

Engine control fuse is 'supposed' to go where it says it goes, the 'E'ngine'C'ontrol'U'nit.

[S14-NEO]

ive got the FSM here in front of me and it looks like the info you need pertaining to that wire is on page EC-100. its a wire for the EGR function..and its get its power from a 10amp fuse in the relay box on the passenger side fender well. it also looks like its power is directly supplied to it when the ignition is turned on. power is supplied to the 10amp fuse from the ignition switch on the wire that is R/B...hope this helps

[lilskyline240]

yeah thats fuse im talking about. I checked it out in the FSM. SO when i turn the ignition on and power goes through that wire when it hits my Upper harness it blows the fuse. If i have this solid brown wire not connected then it doesnt blow the fuse. Im not sure what this wire goes to in my harness tho

heres a picture of the wire cut

[S14-NEO]

hey find my AIM in my profile and hit me up..we can talk some while im on here...if not my AIM is S14MARKSR

[lilskyline240]

i added you to my buddy list. Im not on much tho. Ill try to be on tomorrow around noonish tho

[lilskyline240]

well i think ima send my Harness out to get looked at

[Flicktitty]

well i think ima send my Harness out to get looked at

i'll trade you Liz's coupe for yours plus uhm a hi 5 lol.

Can't wait till you get this car straighted out.

[danb8586]

if you already had this problem on 2 other engines with other wiring harness why would you think its your wiring for the rb. id try grounding everything first just to eliminate that and check all your connections for the battery and make sure the battery and engine has a good ground.

[lilskyline240]

because of the problem with when i hook up this one brown wire that it blows the engine control fuse. there is a short somewhere in the harness. This way i can totally rule the harness out once i get it back. while its gone im going to Run more ground wires and stuff

[WhatsADSM]

Once I get some free time I can probably give you a hand. Is the car still running or did you send the harness in?