Jakemarchildon20

Hey guys I'm new too this site but been looking around a while for the cure for this problem my FD is having and I hope someone could please help me.

I own a 92 FD JDM. Mild mods, exhaust,hks boost controller, apex'i Safc, hks intake. Generally run around 10psi.
114000km.

My problem started out of the blue where as soon as reach boost it jerks/bucks erratically until I back off so I'm not boosting. It idles solid around 860-880 rpm. Can rev it up in neutral no problems. If I drive it without hitting boost it's fine. It's almost like it is hitting a wall, rpms shoot up and down, poping out exhaust, A/F leans out, until I let off. No smoke

I have not touched anything too make this happen. I have been researching for a while now and come across a lot of different possibilitys. I'm just trying too find out what too start with, just need someone with experience too help with this shitty situation.

Tps, vac leak, boost leak, alternator, bov, injectors, fuel pump, charge valve, coil, ecu, o2 sensor, limp mode..?.??.!?.? Have I left anything out lol...please help. I will start checking the simpler things like vaccum leaks. Just would greatly appreciate and help you guys could give me, thanks.

peejay

It sounds like an ignition fault, either worn plugs or arcing wires or weak coils.

Howard Coleman

iTrader: (6)

"bucking" is generally a global problem...

in other words either the fuel supply (effecting all injectors) or an elec problem effecting all the coils.

my bet is fuel. i believe you are saying your AFRs go lean?

peejay

I was thinking that too but if it is only when under boost, that seems to indicate a load dependent problem.

Unless you are thinking maybe the fuel pump is so worn that it can't make enough PRESSURE anymore even if it can make volume., make just enough pressure for sub-atmospheric but can't follow the pressure increases with boost. Certainly it is easier to test.


An ignition misfire shows lean on an O2 sensor.

j9fd3s

iTrader: (3)

you should check it for codes, with a JDM car you either need the code checker, or an LED, as there is no check engine light.

eage8

iTrader: (9)

Bad secondary fuel injector?

RotaryEvolution

iTrader: (30)

check the tps

Jakemarchildon20

Another thing I failed too mention was it happend before a couple times. Then went away. Now it's back. Does it matter that my battery was completely dead ? I boosted the car warmed it up. Then took it out and it happend. I Did a oil change. Battery is being replaced 2day. Did my plugs/ wires about 3 months b4 problem started. I also have a hks boost controller (evc).

Thanks for the ideas boys. I am considering checking the fuel system. Is there a schrader valve anywhere on this system?

Will be checking the tps also, I was researching this problem and a fellow FD owner posted a video( title rx-7 problems)with the close to identically the issue I am having and it ended up being the tps... So makes sence too check that first. Thanks for the help guys keep it comming.

RotaryEvolution

iTrader: (30)

no on the schraeder valve, gotta remove the hose to the hardline on the engine by the oil filter.

Jakemarchildon20

Ok been looking for it thanks. Once I get it hooked up, will it tell me if there's a problem under load(boosting), I'm thinking I will have to be driving with the gauge being visable..?

I checked the connector on the tps and it looks ok. The prongs that the connector fit into look pretty clean but there are two different colour pins starting at the top it's gold, silverish.., gold, silverish.. I guess they could be corroded hard too tell but def different colors. Could be normal? Need a multimeter to check it's functionality. Grabbing one today.. Thanks

RotaryEvolution

iTrader: (30)

usually the problem with the tps is internal, a visual inspection won't give you any signs if the tps itself is bad.

usually you have to drive the car to find a fuel pressure issue but not always. if it's low when idling or free revving then you don't need to move on to a driven load test of the pump.

Jakemarchildon20

Ok yes need to test it with meter got ya.

I was looking at fuel lines near the oil filter I see three hard lines going too rubber hoses but what one do I use?

RotaryEvolution

iTrader: (30)

been a while since i worked on a stock car, iirc the feed line is the one towards the front of the car, the top one is for fuel tank vapors and the rear one nearest the oil filter is the return line. so the front one would be the one to test.

Jakemarchildon20

So the one that has the clip you can see in the picture?

I bought a pressure tester


It can allow me too have it wire in with that T fitting, should I just do that or set it up so I can have it visable when I drive it too test the problem?

I also bought a new battery and multimeter. Fires up nice no smoke idle between 1000-1100 rpm cold, then sits around 760-780 when it's warmed up. I will be working more on her tommorow. Thanks for your insight brother I really appretiat your time.

RotaryEvolution

iTrader: (30)

yeah, the one with the visible compression clamp, use the supplied tee there and place the gauge against the windshield where you can see it and take it for a drive.

Jakemarchildon20

So I checked my tps all numbers are in spec, I checked for a smooth climb from closed to wot and both sides seem smooth, no bouncing and holding volts properly.

green/red

1.23 v closed
3.46 v half
4.98 v open

Black/green had

0.59 v closed
2.4 v half
4.28 v wot
Sounds ok
Next is the fuel pressure

Jakemarchildon20

So I've been researching what kind of readings I should be getting. It's saying I should have 0psi at manifold... Don't know what that means but the reading should be between 34-40 psi? Is that correct??

It's saying idle pressure and pressure under boost can be calculated using vaccum/pressure under those conditions ? Not Shur I fully understand. I'm thinking I need a vaccume tester.. If elaboration can be given it would be awsome lol thanks

RotaryEvolution

iTrader: (30)

32-40 with no vacuum in the intake manifold, which means disconnecting the fuel pressure regulator, which isn't an easy task. if when idling its still in that perimeter you should be ok for the idle test.

for a loaded condition, take your idle pressure and add 8psi(8psi is roughly the change you should see from a 20"Hg idle to 0"Hg of vacuum setting) plus 1 psi per psi of boost you are seeing and it should be nearly equal to the fuel pressure.

Jakemarchildon20

Well I installed the pressure gauge and wierd stuff is happening. Turn the key too the on position and there is no reading. I turn it over and it starts fine. It's reading 32psi steady shut the car off and it's holding pressure. Waited 20 min and it went up by a couple psi?? Thought if anything it would leak down... I really hope I did it to the right one... I'll add pic




Tell me it's the right one lol

RotaryEvolution

iTrader: (30)

hard to tell by the pictures but the vapor line would have no pressure ever, so i'm pretty sure you have it correct. no leak down is good, i don't recall if the stock ECU had a pump prime but i don't believe it did so no pressure until crank is normal. so for now everything seems ok with it, if possible drive the car while watching the pressure. it should go up to about 40 psi with a moderate load without boost, see what happens with the pressure when the issue occurs if nothing is jumping out at you.

Jakemarchildon20

Dude I can't thank you enough for the help.
I need to get some air in my one tire, must have a slow leak
Then I will put it too the test. I'll take notes.

Now if the fuel pressure drops off what will it tell
Me? Weak fuel pump I'm guessing?

RotaryEvolution

iTrader: (30)

if pressure drops as load increases then you have a fuel volume issue. a volume issue can be anywhere from the engine to the pump in the tank, being a clogged fuel filter, weak pump, cut in the line from the pump to the sender or even very commonly an electrical issue causing voltage to drop as amperage goes up.

a dead head pressure test will usually rule out a faulty pump and all the tubing from it to the engine. you can do this test by crimping the return line near the fuel filter and tapping the ignition key until the pump turns on and primes the system. you should see about 90psi.

Jakemarchildon20

Ok so I took her out today for the first time in for ever and thank god the problem happend so I can get too the root of this.

So I jimmied up the gauge so I can see it and with moderate load it raises to about 38-39 psi from 32 at idle. As I'm driving my boost gauge is sitting in vaccume portion of the meter as I apply throttle it creeps up too 0 psi and the a/f is around 14:1. Once I step into it the a/f drops off. The more I step into it the more I can hear the blow off valve whooshing Witch I would think is letting the compressed air out. Is it my blowoff valve or waste gate stuck???? I need to reseach that portion a bit more.

I have a s-afc that I am scared too f$ck around with lol. The only thing I changed was my low throttle1000 rpm a/f and added 3% fuel so the idle sits at 14.7:1.

Could this just be the bov? The car runs great other then boosting??? My fuel pressures are exactly what you are pointing out. I don't remember hearing it whoosh when just driving, only when I rev it up when idleing or letting off the throttle when the boost was working.... What do you think?

Jakemarchildon20

Ya it comes out of back of manifold runs parallel
With intakes and stuffs down near fans and rad?? Says hks
On a filter looking thing

Jakemarchildon20

Also found this



It was completely pinched off but on. I took it off of this thing and it made like a depressurizing or pressurizing sound??




What is it



I thought it was a wire with a loose protecting sleeve on it. Should of known. Would this cause a problem?

I'm gonna replace that ASAP

(Add)
I removed it and the car actually idles better it's pulling vaccum through the line from whatever that selonoid thing is. before it was pretty solid rpm wise but it seems too calm it down a bit. Need vacuum hose