supradrift

iTrader: (7)

hello everyone

so i am having trouble with my FD. the car is going completely lean on me when i hit the throttle. it spools up to about 5 psi and then falls flat on its face. it'll hit the 5 psi and then lean with a loud back fire, almost as loud as a gun. however if i ease into the throttle and hold it just a little it will rev all the way out to red line at 0 psi. if u push the throttle just a slight bit more it will go lean and backfire. the car will not rev up feely in neutral if u stomp on the throttle, it leans out at about 3700k and back fires. again it will go if you ease into it. i've checked if the CCA works, checks out okay, i confirmed its getting plenty of fuel pressure while driving the car. I've checked both black vacuum boxes for leaks and no signs of any air leaks. i was starting to suspect my double throttle but that also checked out okay. i checked the actuator for the secondary turbo and that too was good. what else can i check that would have a connection with it leaning out? would the green fuel temp sensor effect this? its basically the only thing i didn't replace on the rail while it was out. could the waste gate actuators have anything to do with it? i mean it only goes to 5psi before it takes a ****. would a poor ground connection cause this?

i've been trying to figure out this issue for quite some time now and in the mist of trying to figure it out i've replaced several things.

it has a NEW series 7/8 vacuum box ( black box under UIM )
has a new turbo duty sensor ( the green double sensor ) AND boost sensor thats under the UIM.
it has a brand new denso fuel pump / filter and i have even replaced the fuel pressure reg. and damper.
i even went as far as wiring a new relay to the pump and bypassing the stock system.
i also sent out my injectors to be cleaned and tested and everything came back okay.
it has a new TPS sensor. new 02 sensor. it has new gaskets for the UIM. TB and the black elbow that goes into the throttle.
i've replaced all the vacuum lines with silicon lines ( i've confirmed every line was seated proper and routed correctly )
i've even checked the check valves and they too seem to be good.
i've checked for boost leaks and nothing.


the car is pretty much stock other than a few things. it is a newer JDM Series 8 engine with that black vacuum box
it has a 3" down pipe, mid pipe and exhaust. - air pump deleted
hard intercooler pipes
stock ecu
greddy intake

it idles at about 800-900 and reads about 15-17 inHg on my boost gauge, @ about 10.9-11.5 A/R


i'm stomped and frustrated at this point, idk what else to check for or where to look. any input would be greatly appreciated

thank you please help!

DaveW

No expert here, but I'm thinking that with your intake and exhaust upgrades, you may be exceeding the the stock ECU and injectors' fuel delivery capability and causing it to go lean when you exceed 5 psi boost. The FD was not made to run large upgrades in airflow - the stock ECU maps and injectors were designed with stock intake and exhaust system in mind. With your mods you probably need an aftermarket ECU.

When I upgraded my FD to the specs in my signature (I still have the stock ECU and Catalytic converter), I had to be careful not to overdo it and exceed the stock ECU's capability or the amount of boost that would lean it out excessively.

DaveW

Another thought - is the line to the boost sensor on the firewall (or wherever yours is) clear and not blocked, and the filter in that line OK? If not, the ECU may not be getting the right boost amount and so not increasing injector duty to handle it.

newtgomez

Are there any codes that are being thrown? Im not familiar with anything that has the black box but my FD has similar mods (Stock ecu, full 3" exhaust, hks hot air mushroom intake, stock twins)

My car has gone as far as 5k rpms with no issues aside from overboosting.

Driving it the other day when I had some wiring in the wrong places, my fuel thermosensor threw a code and my car bucked so hard I couldnt believe it and that was only around 3k rpms.

What do the AFRs read when it leans out? Are your secondaries coming on?

Fritz Flynn

iTrader: (263)

sounds like a classic fuel pressure problem to me

if you don't have a gauge get one

you can also quickly by pass the resistor etc... and run a hot from the battery straight to the pump and this may be a quick way to diagnose if you don't have a gauge.

There are lots of write up on how to bypass the stock wiring to the fuel pump

PS actually just reread and your secondaries may not be working if you are going lean at 3700 rpms when free revving?

supradrift

iTrader: (7)

its possible dave... ecu upgrade is on my wish list. the line leading into the map sensor is fine no kinks or nicks. i can push air through the little filter so i think its good.

i did have a fuel press gauge hooked up to i and drove the car with the gauge and it held pressure.

the A/R gauge goes completely lean and blinks, i let off the gas as soon as i feel it starting to jerk

what would cause the secondaries not to come on? maybe the tps needs adjustment? i did replace it but it idles perfect ( i think ) the idle doesn't bounce or anything

OG BBF

doubt it'll be your tps voltages. Did you ever remove the sensor? Have you tried pulling the secondaries and seeing if they physically spray?

does the problem happen with engine cold and hot? If so you can rule out the fuel temp sensor..

also as mentioned try wiring your pump to a relay for a clean 12v supply.....

4pin relay
terminal 30 to 12v source from battery
terminal 85 to ground.

the wire you want that comes out of the fuel pump cover is if I remember White with red stripe? Thicker one of the lot (someone correct me if I'm wrong).

cut it in 2. Connect the bit coming from the pump to terminal 87 and the other pet loom side to terminal 86.

this will ensure a clean 12v source to the pump without interruption to rule out voltage drop as a possible cause and if it's not the issue a must have mod anyway.

Fritz Flynn

iTrader: (263)

Secondaries could be stuck closed

There are threads on the forum for diagnosing/checking this

ZE Power MX6

iTrader: (157)

^ That, test your secondaries or swap in a spare rail to see if that solves the problem.

supradrift

iTrader: (7)

okay, i will check and post results when i finish testing, just to make sure, from what i was reading all i need to do is push the little pintle in the injector nozzle and fuel should spray out right? if nothing sprays than obviously they are staying stuck closed.

IRPerformance

iTrader: (41)

It sounds like the secondary injectors aren't staging. If you want me to look at the car my shop is in NJ.

Khan Racing

iTrader: (2)

+1 for IRP their work is top notch!

7-XR

iTrader: (7)

Its a stretch but ...ask,bribe,beg a forum member or (a really nice) shop to lend you a PFC to try. If the car works 'normally' then you know what you have to get. With all of those additions and changes the stock ECU isn't getting correct feedback and is probably throwing you into limp mode. By doing this you could figure out if its an ecu problem in 20 minutes give or take.

FührerTüner

iTrader: (5)

When you said you changed the "pump/filter", did you mean the sock on the pump, or the inline filter?

If its not fuel pressure, then its your secondaries not kicking in.

supradrift

iTrader: (7)

okay guys, so i tested my injectors.... i pulled both rails and flipped them over and i used a pick to press the pintles and all 4 sprayed fuel. i also did the tapping method with 12v and ( - ) and each injector clicked and sprayed fuel as they should....
https://www.rx7club.com/3rd-generati...losed-1098631/
this is what i followed.


fuhnortoner... i replaced both the inline filter and the sock on the pump

i did replace the TPS, but it idles fine, it may be out of spec but by a very small margin.
i did re-wire the relay. the pump comes on at 12v and 13.5-14v while running.
problem occurs while cold and at operating temp.


also on a side note, this problem i am having has been happening even before i installed the down pipe ( i found a feed one for a killer deal couldn't pass it up )

scotty305

iTrader: (2)

A loud backfire could indicate a spark cut or spark-related misfire... the loud gunshot sound is usually caused by a whole bunch of unburnt fuel in the exhaust lighting off suddenly. The O2 sensor only measures the result of normal combustion, it can show lean if there was a spark cut or a misfire. Make sure the ignitor is bolted down securely to the chassis, it gets grounded through its mounting bolts. If you've recently swapped spark plugs or disconnected/reconnected the wires for the ignition coils, double-check that all the spark plug wires are going to the correct coils.