Previous owner replaced engine... I'm trying to figure out what's left to do.
 

As I am new to RX7 club i am posting my question here: in the Rotary noob corner. Because I am just that, a Rotary noob. Here’s my intro link: https://www.rx7club.com/introduce-yo.../#post11649227

Anyways, let me inform you with my problem so hopefully you can inform me how to fix my problem... I recently bought a 90 RX7 Turbo II. The engine was replaced by the precious owner and completely put back together, I think. I bought the car as is (non- running) with 97k on the chassis for $3,000. I have been trying to get the car running since the beginning of November.

The car has new belts, restored injectors, new fuel tank and fuel pump with 40K on it, and new fuel filter. Also, new spark plugs, used CAS (I replaced the original and got this one on eBay), Used Ignition coils and igniters (also eBay), fresh oil, and great compression.

When I got the car it had been sitting since 2002 and the middle man who bought the car tried starting it before cleaning out the sitting fuel system and clogged the injectors and fuel rails with rust... hence why I replaced the whole fuel system minus the fuel lines. I know nothing about the replaced engine. All I know is it looks good and has great compression.

I have done a lot of trouble shooting and found my spark was weak. That is why I replaced the coils and igniters. Spark plugs were fouled (replaced as stated). I read the ECU/ECM codes and it threw a 3 saying the CAS is bad (replaced as stated).

Now that you all are up to speed. I have gotten the car started and it runs but it is in limp mode it seems, and I can’t get the timing right. Even with the new CAS the ECU/ECM is still throwing a 3... I read the codes details and found it is possible that the knock sensor may be faulty or unplugged and that will cause the ECU to throw a 3 and the CAS may be fine. Also if the knock sensor is unplugged I hear it may also retard the timing (not sure if true but adds up to my problem).

In the pictures below I present one connector that is unplugged (I suspect the knock sensor). I can’t find where this connector goes and I also can’t find where the knock sensor is... :(

Symptoms: Timing is off, engine won’t stay running for more than 10 seconds and idle is at about 500 just bouncing off not running at times. Car starts only with foot on gas. ECU trouble code 3. One connector unplugged (not sure where it goes).

Please help I love this car and really want it to start! This car is my dream car! :(

Thank you!!

-Joe

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Can't offer any specific answer since my wiring diagrams are for S4s. However, I suggest you download the S5 wiring diagrams & try to match the wire colors / connector location.

The car looks sweet. Good luck with the troubleshooting & rejuvenation.

Hey sorry to hear about your troubles.. I also have a 90 tii. Let me know and I can get you some good pictures of whatever you want. I can try to upload them streight to this thread

Find your wiring book here. Hope it helps.
Foxed.ca - Mazda RX-7 Manuals
Good luck.
T2 for the win.

Thank you for posting!

You may be able to help haha i suspect my engine to be an S4 instead of what should be in the car, an S5...
I'm posting some pictures of parts on my car to see if they are S4 or S5. Now the thing with my car is the engine was replaced. So, i probably have a lot of s5 parts under the hood but i think the block itself is an s4 block.
The big giveaway, i think, is that the knock sensor is not above the spark plugs on the front rotor housing.

If you could confirm that some of the pictures i posted below are the same or different that would be great. Also, a few pictures of your engine would be awesome too (knock sensor would be very helpful) Thanks a bunch :D

Thank you for the link, that helps a lot!
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This is where the knock sensor should be on and S5 engine, but i dont see one there. If you guys could confirm this, that would be disappointing, but very help full none the less haha

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I think this part number matches up with an S5 but as i said before the block is probably the only thing that is S4... I dont know how these guys did it. but it must have been a pain in the butt!

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I don't know what these are called but i believe these are also parts that differ on S4's and S5's, I think haha

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TPS

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Random pic that may be helpful...

Thank you all again,
-Joe

One thing I notice is that if you are trying to run the engine without the Intercooler then the AFM will not be operational as it gets no air.
So if the AFM gets no Air,it can't supply a signal to the ECU to get fuel.
Toss your Intercooler back on and try to start it.

I wish that was the case. I only took the intercooler off for the purpose of these pictures. I only try to start the car with the intercooler on. Thank you though.

Hey, Joe - One other quick thing to check that is different between S4 and S5 engines is the OMP (Oil Metering Pump). On S4s, the pump has a mechanical drive through the front cover. From what I have read on the forum, the S5 OMP is electrical.

If you are right about this being a hybrid S4 block with a lot of S5 externals (and emissions wiring harness), the connector could be for the S5 knock sensor.

Thks to Genetic Drift for the wiring diagram link. I can't tell from the photo whether the connector is two or three wires. If it is three, I think it's the for the OMP position sensor. Page 35 of the wiring diagram shows it in about that location. The connector shape (page 34) looks about right, too. That would match with your S4 block / S5 externals and harness.

Where is the OMP?

I'm pretty sure the connector is only 1 wire. also which wiring diagram did you use off that site? I think i'm looking at the wrong one.

Thank you! thanks to GeneticDrift again too for the link! much appreciated!

look under the alternator on the engine side of it. theres a few sensors under there as i recall. I'm pretty sure theres a water temp sensor thats a single plug down there.

Location of the OMP is the bottom of the front, right corner of the engine - just in front of the exhaust manifold...same for both S4 and S5. The S4 pump is an internal mechanical drive. The S5 pump is an external stepper motor drive.

The Mazdatrix oil injection page has useful images.

Can any S5 guys out there confirm or correct whether the connector shown in the original post is the harness side of the S5 OMP position sensor?

Thank you guys i think i found it. Its hard to tell. But, I don't see any wires coming from the area so i think it is an S4 OMP...

Here are some pictures i took of the area with indications to where i think the OMP is. Please correct me if i'm wrong.

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Thank you, the link was very helpful!

I second that! This would be very helpful! :D
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Also, If the pictures i took are my OMP and my engine is a S4/S5 hybrid. Where is the S4 knock sensor. Will this setup even work? There is no knock sensor control unit under the passenger side dash like there would be on an S4 RX7...

I mean i don't even know what this wire goes to... but considering my cars symptoms i think it points to the knock sensor being unplugged... but, I don't know.

Thanks again guys!
-Joe

I think the response from sp0ngebob was about the knock sensor while mine was about the location of the OMP. Your pics are all of the front driver side of the engine. The OMP is on the fron t passenger side. It is most easily seen from under the car and has 4 banjo fittings w/ plastic tubes that deliver the metered oil to the intake runners. Not sure what you are seeing in your pics...but it is definitely not the OMP.

hahahaha my bad. Yeah sp0ngebob's response makes more sense now... I feel silly lol. Anyways after this snow storm passes by i will try and get some more pictures that are actually the OMP...

Thanks for being so forgiving and helping me so much RobbyWally!

OK! Know that the snow is gone, we can continue with whatever is going on with my engine... Below are some new pictures that i'm hoping are pictures of the OMP...

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If this is the OMP. It looks like it is electrical and not mechanical. So, the only thing on my engine that doesn't match up to being an S5 part is my knock sensor... Which by the way i still cant find! :/ (i looked near the alternator. Do i have to take off the throttle body to see it?)

Thanks for helping again guys! I really appreciate this!

-Joe

NOW haha not know lol

Update
 

I have found the knock sensor and it was located on THE CENTER IRON just below where the oil fill tube connects to the engine. This is the S4 location. I had some trouble finding where the heck that sensor was located, but i found it! :D I made clear the location so some other guy looking for it can find it... Unlike me haha!

Now the important part, the knock sensor was plugged in! So, i still have a single wire unplugged not knowing what it does... Is it possible that there are two knock sensor connections seeing that my engine is indeed a hybrid S4/S5 engine? I'm also thinking that my knock sensor, now knowing it is indeed plugged in, may be faulty. I say this because my ECU is throwing a 3 code as previously stated. The code is for the CAS but i replaced the CAS and the ECU continued to throw a 3... I read that the code can also mean an unplugged knock sensor. But as i said before it is plugged in. Should I replace the knock sensor?

The engine starts and then cuts out after about 10 seconds. The timing is off but close (i don't have a chance to time it because the engine wont stay running).

I'm at a loss here, I don't know what to do. :/

Thanks for helping guys.

-Joe

In my first reply, I suggested trying to match the number and color of the wires and the connector shape on the wiring diagram. I still think that is your best shot. Use the 1991 wiring diagram at the link posted by Genetic Drift. Or, if you post the color(s) of the wire(s) and which harness it is tied to, I'll try to help you out.

Did you ever figure out what the issue was? My s6 engine has the same symptoms.