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Zac's 1998 RX7


ProZac
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Quick dirty hack to read the trouble codes from the ECU:

 

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Gives:

 

12 - Throttle Position Sensor (Full Range) - open or short circuit

18 - Throttle Position Sensor (Narrow Range) - open or short circuit

32 - Secondary Air Switching Valve - open or short circuit

46 - Solenoid Valve, Charge Relief - open or short circuit

 

I took the battery terminals off for a couple of minutes, and pressed the brake pedal (procedure for clearing the trouble codes), and then read them again, and the were the still there. The TPS ones make sense, as Brad did say it needed setting up.

 

Things to investigate, yay.

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First day I get to have a play with this. It's bloody freezing out!

 

I'm going to approach this like I approach my embedded systems design projects. Scientific, Documented, Logical and with NOTHING assumed. I've never played with a rotary before, so it'll be a great learning experience. My experience with modern(ish) EFI systems is pretty large, so that should help me out.

 

So, with nothing assumed, I'll start from basics.

 

What does it need to start and idle correctly?

 

Air (+some compression)

Fuel (in approximately the correct amount)

Spark (at approximately the correct time)

 

Onto testing those three things then.

 

My compression tester is stuffed, so that will have to wait (I've ordered bits to make an electronic rotary compression tester, but more on that as it happens).

 

Fuel is the problem I've been told it has, as in WAAAAY too much, but I'm assuming nothing, so I'll check that. A few things to test here. The easiest of which is that the pulse width going to the injectors is sensible. I've read the the FD injectors are high impedance, and a saturated drive, so testing this should hopefully be pretty easy. Fuel pressure also has to be checked (I'll need to get a bit of gear to do this, it's on the way with the bits for the compression tester). Also the physical side of things, they're side feed injectors, so it would be possible for fuel to be leaking past into the port.

 

Spark can be tested by observation, and with a timing light. Plus running through the FSM details as to what should be where. The only FSM's I've been able to find are USDM series 6 models however, so I'll have to keep this in mind during testing.

 

Right, time to get started! 

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Should be pretty easy to just post that list of faults on an rx7 dedicated site and get some semi expert advice on common causes? I bet it will all be real simple and everyone will palmface when its worked out.

I got a good deal on my mk4 supra for similar reasons (old owner had plumbed a boost controller into the wrong actuator)

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Dell'orto certainly didn't strike me as an idiot though, and I'm sure if it was something super simple he would have figured it out.

 

I had a few people come around today, and then visited with family, so really didn't get much done! I did confirm that the correct HT leads are going to the correct places though.

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Should be pretty easy to just post that list of faults on an rx7 dedicated site and get some semi expert advice on common causes? I bet it will all be real simple and everyone will palmface when its worked out.

I got a good deal on my mk4 supra for similar reasons (old owner had plumbed a boost controller into the wrong actuator)

 

The fault codes there (with the exception of the TPS ones) won't cause the issues it's having, they're purely boost control codes.

I am a little concerned about the lack of MAP sensor code, though if you've not driven it yet that makes sense. That MAP sensor tested out of spec, and was replaced by a good one which tested up fine...which I then had to give back when I sold it

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Good to know, I'll give it a test at uni tomorrow. The specs are in the FSM.

 

Maxted - I was only going to make one, but could possibly make a couple more. Would just have a simple 16x2 LCD readout that would give the three rotor face readings, nothing fancy :-).

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G'day, nice buy. Is it still sequential? ive wired up a few of these and own one running the stock ecu.

You should first decide if you want to keep it sequential twin turbo. Not sure if you've seen the rats nest yet but you are in for a challenge if you want to keep it dead stock. The stock ecu is quite forgiving and will run in limp mode with many sensors unplugged. it will idle in limp mode without the map, IAC, o2 sensor and a variety of other thing sensors missing.

You can tell its in limp mode by the inability to rev it above 3 or 4k rpm and backfiring if you try to. My JDM import does not have a check engine light.

You can quickly check its compression by listening to the chuffs with the plugs out.

I have de-sequential'd a couple of fds and prefer it for simplicity and easy troubleshooting of issues. Check out the service highlights on foxed.ca, that explains the sensor relationships and what you need to run.

I'm happy to help if i can with any questions etc

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Brilliant, info, cheers.

 

Yes, it's still sequential, and I would like to keep it as stock as possible. I really liked the sequential system on a couple I test drove. My understanding was the the 'rats nest' was greatly improved after the series 6, and is a more modular system on the series 7 and up cars? Further down the track, if I'm still not having any luck I'll just isolate it out temporarily if that's possible, and see if that changes things.

 

What you've said certainly seems to point more towards an output issue, rather than an input issue. I ran out of time yesterday, but did manage to scope the front primary injector signal. While cranking it was a nice clean square ware, with the expected big inductive spike , around 50ms in length. Haven't had a chance to scope any thing else out yet, hopefully this weekend. The shape of the signal indicates no wiring faults between the ECU and this injector. I look forward to seeing the rest :-).

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