conde

iTrader: (2)

New Mazda Motor put in 1.5yrs ago about 2000miles on it
New Engine Harness
All New Solenoids (Went Simplified Sequential from this; https://www.rx7club.com/3rd-generati...-turbo-749702/)
Vac Lines are all Silicone
New Stock FPR when I put new motor
Replaced Fuel Filter when I put the new motor in
New fuel pump when i put the new motor in
Removed fuel pulsation damper
Had injectors cleaned by RC Injection about 2 years ago
No Air Pump
All sensors were replaced except for the CAS sensors
Stock intake
Stock FMIC
Pettit Downpipe
Pettit Mid pipe
RB Exhaust
Also Ive been premixing with .5oz per gallon still have OMP thinking of bumping it to 1oz per gallon casue i have no idea if its working or not, I just reinstalled it when i put my new motor with all new lines and everything.

Little back story, had an issue when i first put the motor in and got her runnning it was pretty much running as it is now. Turned out that when i installed the injectors, when i installed one of the secondaries i didnt put enough lube on the o-ring and it didnt sit properly causing it to flood my engine. After i repaired that the car ran perfect for the past 1yr and a half. I have a powerFC with the base map, my AFRs at idle depending on temp outside was about 13.5-14.3 sometimes a little richer when coming to a light. Boosted fine, no boost creep would hit 10 and afrs would be in the 12s. What im saying is car ran amazing...

About a month ago now I went to turn her on after she sat for about 3 weeks, turned it on ran fine for about 5mins and it starts to randomly idle rough. it was about 40degrees outside, it would break up if i try to give it gas and its running lean. Vacuum is about 300-400mmhg on the powerfc.

What ive done so far:
Changed spark plugs with NGKs
Checked spark with those inline spark testers and had spark on all plugs
Smoke test to check for vac leaks, no vac leaks
Compression tested with those rotary compression testers, 110+ on all faces

Im at fuel pressure, ive checked fuel pressure numerous times now and I think i have a fuel issue. I followed the manual per their instructions. I have about 30-34psi at the pump with the other end of the gauge plugged, which i think is low and may be my issue? I jumped F/P at the diag box and had BAT voltage at the pump and it still doesnt pass 35 sometimes it will only get to 30. I also tried fuel pressure at the engine where the lines come into the motor, same pressure but if i squeeze the return line nothing happens? I assumed it would increase pressure, but no change at all. All these tests were with the car off just jumping the F/P at the diag box. I would also like to note that I ran the car low on gas the last time i drove it before fueling up which was dumb on my end. Now not low enough for it to turn off but low that i though maybe it clogged something but, im getting same fuel pressure readings at my pump and at the engine.

I think my fuel pump is my issue with not enough fuel pressure 30-34psi base seems pretty low to run the car on? But im unsure
I will post videos of how the car sounds as well as a video of my Power fc with the sensor check screen and the 8 channel screen.

links:
Thanks
Mike

scotty305

iTrader: (2)

That does sound low to me. The factory workshop manual suggests you should see 36-38psi fuel pressure on the supply line with the engine off (page F-97 in the manual), or 70-107psi if the pump is pushing against a plugged line (page F-101). I haven't checked this on my car, but the test described in the manual seems simple enough. Another test might be to pump fuel into a fuel-safe container and measure the fuel pump's flow rate. From what I've seen online, the factory fuel pump might flow around 200 L/hour at 12V battery voltage, that would be about 3.3 liters per minute.

Do you still have a wideband O2 gauge on the car? What are the AFRs at idle when it's rough?

conde

iTrader: (2)

Just reads lean, I disconnected the vac line at the MAP sensor and it richen up to about high 14s, but doing that would cause the car to run worse

era1oner

iTrader: (1)

WIth a multi-meter I would check to see how many volts are getting to the fuel pump with the "AUX" power on ,while cranking and what volts are with the car on. You should be getting no less than 12 12volts. If the voltage is lower I would recommend you do the fuel pump relay relocation mod to the trunk near the pump, it'll bypass the forward one in the engine bay, This will rule out any power issue getting to the pump. Another thing to check is the tps(fixed my similar issue), with the powerFC commander check these under sensor check: VTA2 closed throttle spec is (.75V-1.25V) open throttle spec(4.8V-5.0V)..VTA1 closed throttle spec(0.1V-0.7V)open spec (4.2V-4.6V) Get these within spec and see if there is any change , good luck

FDAUTO

iTrader: (4)

Sounds pretty typical of a failed o ring at the fuel pump feed stand pipe. Was this set up retained with the fuel pump upgrade? It should have been cut off and replaced with a peice of SUBMERSIBLE fuel hose.

DaleClark

iTrader: (55)

I don't think it's fuel pressure.

That stuttering and shaking running sounds like a few things to me -

- bad engine
- ignition issue
- fuel injector issue

You said you did a compression test with a rotary tester, you are getting solid results? Had a friend who went nuts troubleshooting a problem and it turned out to be a stuck side seal in the engine. That manifested as one rotor face being substantially low.

Next is spark, make 900% sure the plug wires are on correctly. If they are swapped you will get some REALLY weird things happening.

Next would be the coils themselves. If you have a weak or failing coil that could cause this. There is a test in the shop manual for the coils that is pretty spot on, if it passes they are good.

Finally fuel injectors. If you have a stuck injector you could have problems like this. I've gotten to where I'm not a fan of cleaning injectors, it really seems to do more harm than good. It's possible you have a primary injector that is stuck closed and you are running on one rotor.

Dale

conde

iTrader: (2)

Thanks for all the replies,

Per my powerfc, my tps values are where they should be. I checked to make sure that it hadn’t come loose at some point and it was good.

FDAuto
when I replaced mt fuel pump, I used a Supra TT pump that a buddy had laying around which was new in the box. Don’t know how long it sat.. If you’re referring to me cutting off the feed stem on the hanger and replacing it with a hose, then no I did not do that. I replaced the o-ring I did not check the o ring to see if it was okay or test the pump out of the tank.

Daleclark
the last time I had a similar issue it was my one secondary injector was leaking cause the o-ring did not seat right in the rail. Had pretty much the same symptoms as now, with the shaking and rough idle. Although it was a little harder to start cause it kept flooding. I have not ruled out my injector being stuck closed. I’ve pulled my plugs they don’t seem soaked, although my front trailing had a little wetness to it but nothing that would be of major concern I thought.

As far as the compression test, when you say solid results? Are you asking if they were consistent? Cause they were within 5psi if I recall of each other probably less. I only ran the test through once cause when I saw those numbers it was kind of like a load of my chest since this motor is essentially new, but unfortunately out of warranty.

For the spark plug wires I’m pretty certain the wires are on correctly cause the car randomly started doing this after me parking it for 3weeks. Ran perfect the previous 2000miles without issues. When I did the spark plug test I used a inline spark tester and the light shined as bright as I thought it could go but I could be wrong can always retest this.

And the injectors I have not ruled out. I’ve been trying to avoid pulling my manifold just yet. Fuel pressure seemed pretty low to me even at the pump. I thought if the pump can barely get pressure to 34-35 and the car runs at 36-38, I figured I had a low fuel pressure issue mainly cause of the pump. Now I plan on doing what FDAuto suggested and getting rid of the o-ring and retesting the pump and go from there. I also want to mention that I was getting that psi with 12v at the pump, I have not done the fuel pump rewire so from my understanding from what I’ve read at idle my pump is only getting 9v because of the resistor.

I won’t be able to get to the car till the weekend. So I’ll put out updates as I go on. Thanks everyone for the suggestions!

conde

iTrader: (2)

Thought I would give an update to this. After doing more fuel pressure testing the pump I had was only pushing out 30psi I swapped it out for a walbro 255 I got from sakebomb. And it not makes 50psi+ pump pressure. Up front it gets up to 40psi with it hooked up to the fuel system if that’s makes sense to everyone. I also didn’t have much of any fuel pressure drop after turning the pump off and observing it for like 30mins. This did not fix my issue though.

so I decided that it was time to actually put the manifold off and inspect the injectors. I tried pulsing my injectors with bat voltage and come to find out my front primary injector wasn’t pulsing at all. I checked for continuity and resistance on both of them as well and again my front primary injector had nothing! After ordering 2 new primary injectors and putting them in today she runs great and drives like it did before all of this!

hope this helps someone else in the future!

thanks every one!
mike

DaleClark

iTrader: (55)

Thanks for filling us in!

Really fuel pressure is only a problem with load, the car should idle fine even with lower pressure. But it's good that is fixed, that was going to be a problem down the road.

Dale