Ok so I'm sure this has been on the forum somewhere... But I can't seem to find a thread. So if you can point me in the right direction, or if you guys are willing to humor me and help me out anyways that would be awesome.

Ok so here is my issue. I just recently bought this car from someone and I believe it may be a fuel cut problem but it seems like it runs really rich. When I hit the gas it boggs a bit and then sputters. It does exactly what this guys does here:


I was reading on the forums that I could look into a HKS FCD because its reading too much boost, or it was recommended to me to look into the megasquirt to program the ecu better. But frankly I don't have the cash for a new ECU right now. I'm sure this is a common problem but I can't seem to figure out the right way to go with it.

Also its idling at 1500-1700 rpms all the time. I don't know if thats because there are no emissions on it now or if that is normal for the rotary after changing airflow.

Specs:

HKS Intake
Corksport 4" turbo back exhaust
Godspeed FMIC
10mm Plugg wires
Stock Fuel Injectors

No Emissions
No AC

Thanks

 

Proper idling speed is 750rpm. Your timing could be incorrect. The Fast Idle Cam might not be operating properly also. If you press upwards on the throttle linkage at the front of the throttle body does the idle drop?

 

Sounds like tps is way outta wack. You will only get boost cut if your hitting 8-9 psi.

 

When I push up on the throttle linkage it doesn't let up. Seems like it's all the way closed and there is some slack in the cable. Also the TPS could explain idle, but the car hesitating or sputter when I hit the gas would be different right? Makes sense that it would be a timing issue?

 

So I started the car... Idles at 1500 rpm... Unplugged the tps sensor and no change. Stayed at 1500. Is that an indicator that it need to be replaced? (Dumb question I know) but just want to make sure.

 

There's two adjustments for throttle speed. The screw on the BAC and the throttle stop screw.
Depending on what has been removed during the "emission removal" you may have to resort to the throttle cable.

Other things that could raise the idle: Vacuum leak, improperly adjusted throttle dashpots, sticking thermowax.

The thermowax will normally hold the idle up about 1500 until the car warms up. Then it drops down to 750. Does yours just stay at 1500 all the time?

 

Yeah mine stays at 1500 all the time. It's annoying because I'll have to put it in high gears to bogg it down a bit, since its loud and my cruise mph stays up. There are a couple vacuum lines that are just exposed and not plugged off.

 

You could try pressing downwards on the throttle linkage on the back of the throttle body just under the thermowax and see if that drops the idle but doing this is basically the same thing as playing w/the front linkage. The rod of the thermowax should extend as the engine warms up and presses downward against the upside down screw that is part of the throttle linkage.

If the car has cruise control then check that cable.

 

So I was looking at my BAC valve and there is NO vacuum hose attached to the front nipple. Front as in facing the radiator. There is one however attached to the back. But don't know where the front one would go to. I'll update on the thermowax in a bit. I don't think it's there anymore when the emissions were removed.

 

ok so while i was driving home from work, i decided to turn on the ac (even thought there isnt any) to see if i was getting an exhaust smell from the engine bay or something. BUT when the cool air was blowing i jumped on the gas to get around someone and there was no sputtering, or hesitation at all. But when i put it on HOT air it will start to sputter again at acceleration. Also when i keep it running with the cool air, the engine temp will slightly go up. It will idle slightly higher when its on cold air, and then a little lower when its on hot air.

Also there is a missing vacuum hose from the bottom of the BAC and from the front of it as i said earlier. Only the rear hose is still connected.

What do you guys think?

 

Kind of sounds like the ECU is adding more fuel and idle adjustment to compensate for what it thinks would be the load of having AC on

 

New symptom. Popped a 7.5 fuse for all my dash gauges and sputtering seemed to stop or lessen a LOT. but when I put a new fuse in, sputtering came back full force. Is that because the ECU is linked directly to the gauges?

 

The BAC HAS NO VACUUM NIPPLES.
None, zero, nada.

It gets metered air and has two water lines (an IN and an OUT) but NO VACUUM.

 

The Meter fuse is responsible for powering the gauges and it's also responsible for powering a host of other items.

 

are you saying that like in the video you get a sputtering fuel cut when you step on it around 4k rpm and up? how much boost are you pushing when you hit the wall and have you ported your wastegate, because with a 4" turbo back with stock fueling and no boost control you are definately going to boost spike enough to hit fuel cut, obviously with light throttle/low boost, you can get past that rpm.idle problem is probably unrelated.

 

another thing to check is the functionality of the fuel pump resistor relay. mine was faulty when i first got my car going and was stuck in 9v. running that lean my car did what occurred in that video. you can check this easily with a multimeter hooked up at the pump while driving. also are your secondaries functioning would be another point to check up on. all this info i give as you say it seems like its rich but your mods and video suggest lean.

 

Yes it seems that the boost gauge is readin way high and It happens between 3-4k rpms. I don't have a restricted pill in the pressure sensor line.. (Not sure if that is an issue). So I have looked at possible FCDs and suspected that I may be spiking in my boost. But didn't think I was really pushing that much more power. I have never looked into porting the waste gate... And links to other places that may help me in that?

 

http://fc3spro.com/TECH/HOWTO/ZWG/zwg.html the how to for series 5 is on there somewhere too. You're gonna wanna address adding fuel too as with a 4" exhaust I don't know that wastegate porting will allow enough to drop the boost sufficiently.and a fcd.or get an after market piggyback or standalone.

Sent from my GT-I9100 using RX7Club

 

But like I was getting at before, don't just port the wg and install a dvd and drive.I would check all the fuel components thoroughly. Pump, pump relay, injectors, pulsation dampener.if there's any chance of higher boost you want fuel system to be up to it.trust me I went through it all the hard way and luckily no motor blow in the process but I was lucky.

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Haha can't edit.fcd not dvd.

Sent from my GT-I9100 using RX7Club

 

So I installed a racing beat fcd and it took about 70% of the spitter/hesitation away. Still seems to be running lean. Was going to be looking into a new fuel pump, seeing how this one is 26 years old and check all relays. Either way I'm excited that I'm at least able to drive in it to work.

 

How much boost are you hitting? The stock fuel system/ecu is only good up to 9 psi even with a fcd.

The stock ecu doesn't retard timing after 9 psi, nor can the fuel system handle more than that.

Don't run anymore than that, even if its letting you its a ticking time bomb and I'd hate to see another member blow their engine.

You can control the boost with your foot and if you don't have a boost gauge I highly suggest getting one and not running wot.

 

So my fcd worked fine... Now doesn't work at all. There was a fuel cut switch installed before for when it's flooding and I fear it might have screwed up my fcd. But it still seems like it's passing through power wise. Like the boost gauge came back and the the relay still runs through the fcd, but it isn't doing what it's supposed to.

 

If you're running lean that's bad man.

 

Check the throttle stop screw. Unlock the little nut and turn counter clockwise and see if that does anything. Just to make sure, since you did buy a used car I'd check all the stupid stuff, pull out the CAS sensor and check if it is aligned.

Fuel cut happens past 9 psi as someone mentiopned. ..more like 12 psi but that's without an FCD.

Your setup is asking for trouble. A stock TII pump is safe to about 250hp.
Your setup now is maxing out the injectors to almost 100% duty cycle and maxing out the pump.
There's a LOT of fake Walbro so if you have that, check to make sure it is a Walbro.
A genuine Walbro has metal gears inside (look into the inlet ) and fake ones have plastic gears (big weight difference too).
Some idiots install large secondaries with no fuel control. That will cause huge hesitation and bog after 4000rpm.
Remember, look for stupid stuff and you will find it.


I'd check:
fuel pump
injectors
ECU grounds