RX7 FD wont rev past 3k RPM!! - Page 3 - RX7Club.com - Mazda RX7 Forum

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RX7 FD wont rev past 3k RPM!!

Old 07-22-18, 12:45 PM
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Hey Guys,

So I tested the coils outside the car - hooked up to battery just to double check that the Leadinf coil was in fact dead. It had life and was sparking when tested outside the car.

Installed the coil back in the car and tested the leading spark plugs wires individually this time and they are firing.

The pic above shows where the ground is located (red circle) and wondered if you guys use this as your ground as well?? I was wondering if green circle would be a better ground location.

Tested the ignitor as well and the ignitor is functioning.

Still waiting on my PFC

Cheers
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Old 07-22-18, 01:38 PM
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Had a convo with a friend and he is wondering if maybe the Rotors "timing" is out. Perhaps the Rotors were installed in the same position in each housing. If that makes sense? I am doubtful as I believe the engine was rebuilt to proper specs, but just throwing it out there to see what you guys think.

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Old 07-23-18, 09:26 PM
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bump !
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Old 07-24-18, 07:32 PM
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Who put the engine together? I never seen engine with the rotors aligned the same. My head hurts now.....! Take a bunch of pic of the engine bay with much detail as you can. It would be nice to see a video of the car in action too. I would rip everything apart and do it again.
side note, just because the coils are firing doesn't mean they are not weak under load. All of my coils tested fine, but I swapped them and fixed the issue. Did you fix the voltage on the fuel pump?
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Old 07-24-18, 08:48 PM
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Originally Posted by Red94fd View Post
Who put the engine together? I never seen engine with the rotors aligned the same. My head hurts now.....! Take a bunch of pic of the engine bay with much detail as you can. It would be nice to see a video of the car in action too. I would rip everything apart and do it again.
side note, just because the coils are firing doesn't mean they are not weak under load. All of my coils tested fine, but I swapped them and fixed the issue. Did you fix the voltage on the fuel pump?
Hey Red94fd,
Lol my head hurts too. The engine was built by someone with years of experience and that owns or has owned several FDs, RX3's and RX4's all with modified engines. I doubt the engine wasn't put together well, it just happened to come up in a convo with a fellow RX7 enthusiast. So I said what the hell I might as well ask the question in here see if anyone had heard or experienced that before. Not saying a mistake can't be made we are all human but I doubt that is the issue. It sounds to me purely electrical.

I'm thinking to change the coils and take it from there along with the computer.

Yes I did the fuel pump rewire and same result. I even had the fuel pump hooked up straight to the battery just to test it out and the problem still existed.

I am wondering though if there might be a short somewhere in the wire loom especially on the coil wire loom. When I tested the coils in the car the leading gave zero spark. I tested both at the same time (as in plug wires). Then I took them out and tested them and they were a bit weak but still firing. Thennn I placed them back in the car and tested one leading coil at a time (only removed one spark plug wire and tested one at a time), the coil fired the spark plug and was pretty strong.
I do take your point about the car being under load though which is why I might just swap out the old coils for a new set.

Thanks for the input. Really appreciated.

Cheers
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Old 07-24-18, 10:19 PM
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Just a thought. I had ignition trouble a few years ago including misfires and some hesitation at higher rpms, likely also misfires. I had just road tuned the car and was testing my new uploaded fuel map with minimal changes in the cruise area only, when the car had a major pre-detonation at only half throttle and I blew an apex seal. After the rebuild, I was still seeing some of the same problems and pulled all the coils and tested them and bought another used ignitor and a new HKS Twinpower. Everything checked out with the coil testing fine by the manual standards. I didn't trust the coils, so I had an old engineering buddy with high end testing equipment check my coils. BAD lead after repeated charge/discharge cycles and OK trailing's. My buddy believes the lead coil may have misfired during my testing run and helped blow my engine. I bought all new stock coils and all the problems went away. Just saying, the intense heat our engines put out over the years kill these coils over time. I would consider buying new stock coil/coils, leading at least, to see if this helps. The wiring to the coils I also changed. Mazda did still make this small harness and it is not that expensive.
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Old 07-25-18, 08:17 AM
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Originally Posted by mikejokich View Post
Just a thought. I had ignition trouble a few years ago including misfires and some hesitation at higher rpms, likely also misfires. I had just road tuned the car and was testing my new uploaded fuel map with minimal changes in the cruise area only, when the car had a major pre-detonation at only half throttle and I blew an apex seal. After the rebuild, I was still seeing some of the same problems and pulled all the coils and tested them and bought another used ignitor and a new HKS Twinpower. Everything checked out with the coil testing fine by the manual standards. I didn't trust the coils, so I had an old engineering buddy with high end testing equipment check my coils. BAD lead after repeated charge/discharge cycles and OK trailing's. My buddy believes the lead coil may have misfired during my testing run and helped blow my engine. I bought all new stock coils and all the problems went away. Just saying, the intense heat our engines put out over the years kill these coils over time. I would consider buying new stock coil/coils, leading at least, to see if this helps. The wiring to the coils I also changed. Mazda did still make this small harness and it is not that expensive.
Mike
Thanks Mike,
I might as well change the coils and see how it reacts.

Also, by chance do you have a link to that coil wire harness? If not, I will do some research. I might as well change the wires as well.

Appreciate the help!

Cheers

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Old 07-25-18, 08:30 AM
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Here is the OEM stock number for the wiring harness and the cost with my typical 33% discount I get.N3A3-18-05ZWiring Engine$72.931$72.93
Mike
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Old 07-25-18, 08:58 AM
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Originally Posted by mikejokich View Post
Here is the OEM stock number for the wiring harness and the cost with my typical 33% discount I get.N3A3-18-05ZWiring Engine$72.931$72.93
Mike
Thanks Mike. I assume this will work for the RHD RX7's as well? If not, I found it directly from Japan that will fit my car based on chassis number.

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Old 07-25-18, 10:19 AM
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I don't know if it will fit a RHD. Mine is a USDM LHD.
Mike
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Old 07-25-18, 11:44 AM
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Originally Posted by mikejokich View Post
I don't know if it will fit a RHD. Mine is a USDM LHD.
Mike
Thanks Mike,
I will do some research into it

Cheers
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Old 07-26-18, 09:36 AM
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It's impossible to build a motor with the rotors out of time and have it run. If somehow you put it together with the rotors out of time the motor wouldn't be able to spin, it would lock up.

Dale
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Old 07-26-18, 10:00 AM
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Originally Posted by DaleClark View Post
It's impossible to build a motor with the rotors out of time and have it run. If somehow you put it together with the rotors out of time the motor wouldn't be able to spin, it would lock up.

Dale
Thanks Dale, well thats good news lol
When I was testing the coils/spark plugs the motor sounded very healthy in terms of compression on the rotors. New Apex seals and springs during the rebuild. Among other things

I will be ordering the new coils and the harness soon enough. Maybe even a new set of spark plug wires just to freshen everything up. Then test and post any updates.

Cheers
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Old 08-11-18, 11:24 PM
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Hey guys,

Update: I changed all three coils to brand new OEM coils - Leading and both Trailing. Changed the coil wire harness with the updated one offered by Mazda. Changed the spark plug wires to new OEM. And changed the spark plugs to new OEM ones - engine was flooding and had a spare set so I swapped them out.
The problem is STILL there. Idle is horrible and won't rev past 3,000 RPM!! After that all I get is massive backfires that are very loud. I am on the brink of giving up with this car. The last hoorah will be the Apexi Power FC. If that doesnt fix it then it's for sale as is where is.

I will be adding in the next couple weeks
1. A grounding kit. Simple one. The entire car was repainted. Exterior and engine bay
2. Looking into the harness from the ECU for any botched or broken wiring. Anyone rebuilds harnesses??? My wiring skills aren't great

I am all out of ideas so if anyone has anything else I could try please let me know. Thanks for all the help so far. Appreciated.

Cheers
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Old 08-12-18, 12:25 AM
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You can get a new harness from Ray crowe
for $850 if you think thatís the issue. [email protected]
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Old 08-12-18, 09:36 AM
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Originally Posted by live2drive15 View Post
You can get a new harness from Ray crowe
for $850 if you think thatís the issue. [email protected]
Thanks alot. I will send him an email. Hope he can source a RHD Efini harness

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Old 08-12-18, 03:44 PM
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Some further developments.

This morning I moved the car out from the garage. It idled for a couple minutes then I turned it off. As I was walking back towards the house I passed the rear of the car and noticed white smoke coming out the muffler, very slowly and not very thick. Lasted a few minutes. Not very long. Outside was very warm so It's not like starting a car for the first time on a cold morning.

I think an injector might be stuck open or getting a continuous electrical signal. Which would explain the car fouling plugs easily and having trouble revving out, plus the poor idle. It's constantly dumping gas into the engine at all the wrong times. I am going to run some tests on the wires leading to the primaries and secondaries (continuity etc). If all is good with the wires, I will move on to the injectors to see if any are stuck wide open.

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Old 08-14-18, 10:37 PM
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Is this a stock secondary injector? 850cc? There are no markings on it really.


Tested all wires to the injectors all seems fine. They check out ok.

I am guessing one of the injectors might be stuck open. I will be testing each injector.
Interestingly enough I pulled the secondaries and they were 1300cc RC injectors. And I believe the primaries are 850cc. The ECU is stock so I'm not sure how this would even run properly. Got the car from Japan so who knows how they did all this. No clue.

I'm thinking to get a set of stock injectors and go from there. Or test these and ensure they aren't stuck wide open and then use the Power FC to tune them.
Your thoughts?

Also, when at idle do the secondaries shoot gas at all? Or is it only under boost above 4-4,500RPM?

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Old 08-15-18, 12:03 AM
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No wonder you are flooding. You cannot run larger injectors on the stock computer without some type of remapping. You either have to go back to the stock 550/850cc setup or I would simply install the PowerFC and you can run these injectors as long as they are OK. The 850cc primaries will make it a little harder to tune idle, but I did it without a lot of problems on my setup 10 years ago. The bored out 1300cc RC injectors are known to stick open, which may be your problem. My current setup is 550cc RC primaries and 2200ID secondaries using the Rotary Performance secondary fuel rail. Works great and enough fuel for any twin setup and even most low to mid power single turbo setups.
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Old 08-15-18, 07:50 AM
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Originally Posted by mikejokich View Post
No wonder you are flooding. You cannot run larger injectors on the stock computer without some type of remapping. You either have to go back to the stock 550/850cc setup or I would simply install the PowerFC and you can run these injectors as long as they are OK. The 850cc primaries will make it a little harder to tune idle, but I did it without a lot of problems on my setup 10 years ago. The bored out 1300cc RC injectors are known to stick open, which may be your problem. My current setup is 550cc RC primaries and 2200ID secondaries using the Rotary Performance secondary fuel rail. Works great and enough fuel for any twin setup and even most low to mid power single turbo setups.
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Thanks Mike. Appreciate the help.

I am not sure if the injectors were changed during the rebuild without my knowledge, but I remember distinctively when the car came from Japan it idled fine, revved out no problems. So it is a mystery at this point.
Will be testing the injectors soon to see if any are stuck wide open. I'm on the fence at the moment - go back stock 550/850cc, run stock computer OR if these injectors checkout ok then simply use the PFC. Decisions lol!

Anyone know where is the best place to get some 550/850cc new??

Cheers
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Old 08-15-18, 12:43 PM
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Originally Posted by Trinityevo13 View Post
Thanks Mike. Appreciate the help.

I am not sure if the injectors were changed during the rebuild without my knowledge, but I remember distinctively when the car came from Japan it idled fine, revved out no problems. So it is a mystery at this point.
Will be testing the injectors soon to see if any are stuck wide open. I'm on the fence at the moment - go back stock 550/850cc, run stock computer OR if these injectors checkout ok then simply use the PFC. Decisions lol!

Anyone know where is the best place to get some 550/850cc new??

Cheers
rockauto. The "STANDARD MOTOR PRODUCTS" are repackaged new DENSO injectors. Same as OEM.
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Old 08-15-18, 02:27 PM
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Originally Posted by cymfc3s View Post
rockauto. The "STANDARD MOTOR PRODUCTS" are repackaged new DENSO injectors. Same as OEM.
Thanks cymfc3s. Saw the injectors on their site. Will more than likely order from them.

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Old 08-17-18, 08:03 AM
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UPDATE:

Tested the injectors last night and the "brown" (pic above) ones that were located in the primary position were ok and not clogged. I believe they are 850cc but no way to tell for sure.

The RC 1300cc on the other hand that were in the secondary position.....both injectors stuck wide open!!! Dumping gas non-stop in the engine. So we might have the culprit. Will be changing back to stock 550/850cc setup and then use the PFC at a later date to better tune the car.

Will post up once I have the new injectors installed. Thanks for all the help guys, much appreciated

Cheers
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Old 08-27-18, 09:34 AM
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Rock Auto doesn't have the injectors in stock

Anyone know where else might have the 550/850cc combo?

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Old 08-27-18, 01:18 PM
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Try Ari at Rotary Performance , now Reliable Performance, RX7.COM Performance and Repair Parts for RX-7 and RX-8.
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