Kevin Ingraham

So a bit of background:

I just bought this FD on the west coast and drove it home in the Midwest, about 2000 miles, over Memorial Day weekend. Went without a hitch! I’ve driven the car a few times since then, maybe 20-30 miles total. Last weekend, the filler cap was allowing some coolant to push out past the seal (it was an aftermarket cap with a spring).. Car never overheated when that happened, I just smelled a bit of coolant as I was pulling onto my street, so I popped the hood and noticed it when i got home. Coolant reservoir is sitting at full, no problem.

I just replaced it with a OEM cap and took it for a drive tonight to make sure it’s solid.. well, good news is that the cap worked and no more coolant is leaking.

the bad news is that I got a CEL under normal driving conditions (wasn’t getting into it or anything). It’s like it misfired and the engine hesitated for a sec, then CEL, then it drove normally - though down on power from Limp mode. I pulled off the road about 2 miles up when it was safe, it idled fine. Popped the hood and no issues that I could see. I turned it off, let it sit for ~15 min. Turned it back on, fires right up. CEL stayed on, but it idled and ran OK. So I drove it home (~10 miles).

When I got it home, I turned it off and let it sit again for maybe 20 min, then went to check the codes. I disconnected the neg terminal on the battery for ~60 seconds, reconnected it, jumped TEN and GND in the diagnostic connector, and started the car. It fired right up, but the idle was pretty rough. Turned it off after about 30 seconds... then checked the codes:

20 30 31 33 38 39 40


Per the CEL guide, that corresponds to these sensors:

20 Metering Oil Pump Position Sensor - open or short circuit

30 Solenoid valve, split air bypass - open or short circuit

31 Secondary Air Bypass Valve - open or short circuit

33 Solenoid Valve, port air bypass - open or short circuit

38 Solenoid Valve, Accelerated Warmup System - open or short circuit

39 Solenoid Valve, Relief 2 - open or short circuit

40 Solenoid Valve, Purge Control - open or short circuit


I plan on letting it sit over night, disconnecting the battery again, starting it back up cold, and seeing if I still get the same rough idle and if all the faults persist.

Does anyone have insight on how to start troubleshooting this or what could cause all of these faults to hit at the same time? some of these seem random and unrelated, like maybe its a short in the harness?

I am very handy and absolutely comfortable turning a wrench, but this is my first rotary engine so I’m just a bit out of my comfort zone, here. I figured I would check with the internet hivemind before blindly starting to mess with the car.. hoping that one of you much more knowledgeable people can point me in the right direction.

AE_Racer

iTrader: (1)

Not familiar with the issue but it could be your coolant mishap is related. With all of those solenoid codes, id be checking your coolant hoses that go to the throttle body and such. Maybe you have a leak that sprayed those connectors.

Also, the factory temperature guage is terrible and doesnt move to HOT until its really hot. If you dont have another monitor I would strongly consider it, or check out the linearization mod for the stock one atleast.

Kevin Ingraham

I have all new hoses coming (ordered them from Mazda last week), so that’s already the plan! However, the engine was dry when I pulled over last night so unfortunately that is not likely the issue.

the gauge supposedly is already linearized by one of the previous owners. I have never seen it get hotter than the lower 1/3 of the gauge. Last night, it stayed at the very bottom of the gauge barely registering (staying right on top of the ‘C’) as I was cruising around.

DaleClark

iTrader: (55)

What year is the car? Any mods? Mileage?

Yeah I don't think all of those sensors are having problems at the same time. It's either, as stated, a connector got wet or something and freaked out the ECU or you have a problem with the ECU wiring harness. I think many of those outputs share a common 12v wire, could be something with that.

That's interesting that the gauge stayed that cold when driving around. May also want to look at replacing the thermostat when you are doing the hoses. Get a Mazda OEM thermostat, the parts store ones WILL fail on you.

Dale

Kevin Ingraham

The car is a 1994. engine was rebuilt ~50k miles ago, really good compression (11x psi on all faces)... supposedly it has a very mild street port. OMP supposedly replaced at this time, as well. Twins were recently replaced with factory new, old stock by the previous owner with a ported wastegate. Car's running AMSOil full synthetic. I am not premixing.

Modifications I know of:
- simplified emissions/block off plate/EGR relay to fool ECU
- rats nest simplified
- silicone vacuum hoses
- Koyo radiator
- Racing Beat DP and catback (stock cat still in place)
- aluminum AST
- BOV vented to the atmosphere
- stock airbox mod
- J&S knockguard

So there are a couple of things worth noting. First, there's a bit of boost creep/spike, I believe. it will boost up to 12psi... it's on the stock ECU. previous owner claimed that it has a tune to accommodate for that, but I don't know. I have been babying it (basically keeping it under ~5psi of boost) for now. I planned on bringing it to a local shop to get it on the Dyno with a sniffer to check AFRs and make sure it's not running into fueling issues and going lean.

The J&S knockguard has a AFR gauge (it's a series of little led lights). I'm not sure how this is registering, whether it actually has a wideband sensor plugged into the exhaust or if it's reading from a signal provided by the ECU. when cruising at speed with very minimal throttle input, it's ALL over the place, swinging wildly from <10 to >16.. I think that's just an issue with registering a proper reading under low load. as soon as I put my foot in it at all, it falls down to where it should (11-12 AFR). This is likely a non-issue, but I figured I'd note it, lol.

To your point about the thermostat, totally agree. I tend to go WAY overboard with fixing things because I hate dealing with residual issues.. so a simple leaking filler cap? I ordered all new (Mazda OEM everything) hoses, new filler cap, new thermostat, and I bought an S5 thermoswitch to install because the internet said that's a smart mod. WAY overboard lol. but I won't have to mess with coolant system for a good while after this, hopefully.

I come from the wonderful world of BMW ownership in the past, so I'm used to getting OE replacements for sensors and most parts on any car... heck, even my shitbox Jeep XJ usually gets OE replacement stuff lol.

Sgtblue

iTrader: (16)

Wondering about your ECU and what the PO meant. A rechipped stock ECU maybe? You might want to look it over for labeling.
Not sure anymore, but out of all the codes I think only #20, the MOP position sensor, will cause limp mode.

Kevin Ingraham

Yeah, same boat. The PO was very upfront and honest about stuff, good guy for sure. He said the guy he bought it from is who had the engine rebuilt and who put the tune on it, he couldn't 100% confirm because he isn't the one that did it. So it's been running as-is (12psi) for a while, it's seen the track before in this state... I'd imagine if it was running into fueling or straight up on the stock ECU untuned it would have had a problem by now. But that's not something I want to leave to chance, hence wanting to get it on a dyno with a sniffer to confirm that it's solid.

I'll pull the panel off the floorboard and take a peek at the ECU, see if there are any stickers or indications it has been chipped.

#20 code, scares me that it's MOP... does anyone know specifically what/if I should be concerned about with that? Does that mean there's potential the MOP is not functioning/injecting oil? There seem to be a few codes for the MOP.. (26, 27, 37, etc.) I'm only getting 20.

Kevin Ingraham

UPDATE: Went and cleared the codes just now (disconnect negative terminal for 30+ seconds, then held brake pedal down for 20+ seconds, then reconnected negative terminal).

I did NOT try to start the car. only put it in the ON position after doing that procedure. I'm still getting codes: 20, 30, 33, 38, 39, 40. Code 31 did not register, though.

I pulled the passenger side panel off and the ECU doesn't seem to have any indications of being messed with/modified/chipped (not that it means it wasn't, I just didn't see any stickers or anything at cursory glance), Just the J&S Safeguard being velcro'd to it.

SpinningDorito

iTrader: (2)

Seems like an electrical issue somewhere if the codes aren't consistent. I'd check your battery, and all of your grounding points. Might save you some headache if you find one that is loose/missing/corroded. The only one I remember that is hard to access is under the rats nest (which is probably the ground for all the solenoids, not sure if the OMP uses it too) but you should be able to check the rest pretty easily first.

I agree with the earlier comments to also check out all your small coolant hoses for a leak. Some of them are pretty hard to get eyes on, but one of those little cheap snake cameras should make it pretty easy. I'd also grab a multimeter if you don't have one, because you may need to start checking continuity on some of these circuits to narrow down the issue.

Kevin Ingraham

Yeah, especially with DaveClark saying that at least a few of these solenoids likely share a common 12v, it certainly sounds electrical. I think I might just pop the upper intake manifold off and start rooting around around the solenoid pack/rats nest/whatever. seeing if I can find anything in there like loose connection or a wire grounding out. I'll likely need to get in there to change some of the coolant hoses, anyways.

Ughhh, I hate chasing electrical issues!! /rant.

Thanks guys for the suggestions.. I'll report back if I find anything!

AE_Racer

iTrader: (1)

Looks like you're on the right track.

Make sure you've got a strong back and a variety of needle nose pliers for that coolant hose job. The turbo hoses are a lot of fun

Kevin Ingraham

Bahaha, oh, it's lowered, too... and shoved into my single car garage with all my tools, shelving, bicycle, motorcycle, and lawnmower. I'm sure this job will be a hoot and a holler! RIP my back, knuckles, etc.

DaleClark

iTrader: (55)

The J&S is an OLD relic from a long time ago. The AFR it's showing is from the stock O2 sensor which is totally useless for anything.

It may be tapped into a lot of the ECU's wiring and that could be a source of a problem, a bad or loose connection.

Dale

Kevin Ingraham

You know, that's a good call. I did detail the car last weekend and move the little gauge dealy that comes off it around a bit when doing so. That might actually be where I start then and see if there's anything loose/disconnected/fishy in the passenger side panel first!

DaleClark

iTrader: (55)

Most times an ECU that's chipped has some sort of sticker or something on it so you know it's been chipped. If there's nothing on the outside you may want to remove the covers and open the ECU up. Chipped ECU's typically have a daughter board with a new ROM installed in the ECU. You can post up pics and we can determine if it's original or modified.

Long term I'd look at a PowerFC, you're looking for trouble with a stock ECU with those mods.

Dale

Kevin Ingraham

Yeah, this weekend I think you're right. I'll unbolt the ECU, check it out in more depth (especially looking for loose connections or anything unplugged, per the original issue), but also to dive in and see if it's chipped or totally stock.

I totally agree with getting a PowerFC/standalone ECU being a worthy upgrade, regardless (and especially if it's a stock ECU). I planned on going to a local shop for a dyno and to sniff it to give me a baseline to see how safe it is right now to determine how soon I need to update the control module, basically. Sounds like it would be a good time to get rid of the Knockguard at that time, as well to simplify the system. I'm lucky to have a REALLY good tuner locally that I have a history with who has done rotary tunes before. He also has a Rotary-knowledgeable mechanic at his shop, so I should be in good hands there. Of course, I prefer to do as much as possible myself...

DaleClark

iTrader: (55)

If you haven't read this thread, do so -

https://www.rx7club.com/3rd-generati...added-1104322/

It's a goldmine of information. You can see where you need to modify things and why. It also depends on what your end goal is with the car.

It sounds like your car was modified many years ago (like 20) with what many people were running back then. The RX-7 world has come a long way since then.

Regardless, glad to have you aboard and I hope you can get your car 100% in the near future.

Dale

Kevin Ingraham

Awesome! Thank you for the material. I will dig into it and educate myself some.

I honestly just want a close-to-stock cruiser. So far, the dynamic of the car has been absolutely amazing. It's very balanced, so I am not looking for big power or to modify the car much in the way of power. Reliability is the most important factor for me. With such a light platform, 250-300HP is absolutely plenty.

And thank you for the warm welcome. It's unfortunate my first post is about the car being broken, but I'll get it back up and running soon enough!

Sgtblue

iTrader: (16)

A standalone ECU will solve all your current issues since none generate a CEL or limp mode. And a PFC is probably the most reasonably priced and has good knowledge base and support. But there are other choices and you can discuss them with your tuner. Of those codes however..,you need to resolve any question over whether or not the MOP is functioning properly or immediately begin premixing.

IMO reliability begins with cooling. There are a ton of threads related to that subject. Learning to search and read is golden. Replacing the turbo coolant lines is a good start.

Kevin Ingraham

Is there a good place to start or a walkthrough to confirm the MOP is operating properly? I totally agree, that's mission critical, but I am not sure how to confirm it's functioning.

Sgtblue

iTrader: (16)

There’s a continuity check set out in the Factory Service Manual. That should tell you if you have a real issue or just a connector fouled with leaking coolant.

Kevin Ingraham

awesome. I will find that section in the FSM and check it out!

DaleClark

iTrader: (55)

I'd probably look at putting in a PowerFC and a Walbro fuel pump and leave everything else as-is - stock cat and air pump, etc. With that setup you can easily be around 300hp, lots of good response, very safe and reliable long term. Also won't be stinky .

But, yeah, getting ahead of things. Sort out the wiring issue first. Again I highly suspect the wiring for the J&S. a factory harness doesn't typically randomly mess up or have a break in the wiring. To be honest I'd probably remove the J&S and all the wiring and make sure the ECU harness is in good shape where it plugs into the ECU, that should be where the J&S is plugged in.

Dale

Kevin Ingraham

doing my own research, that’s exactly what I was thinking as well. Walbro or Supra fuel pump and a PFC with a safe tune. Leave everything else basically alone, and the. Just friggen drive it!

but first thing is def first, you don’t go chasing power until it’s fully sorted lol.

I think I will take sgtblue’s advice and test the MOP via the FSM guide to ensure that’s functioning properly, and also yours and at the very least inspect, but possibly delete, the J&S harness connected to the ECU and see where that gets me.

cheers guys, you have been so awesome! Such a friggen helpful community, this is!

SpinningDorito

iTrader: (2)

Harbor freight has some good hose removal pliers that make the job a little easier. There are also those flexible ratcheting hose clamp openers that can save a lot of pain getting the more difficult to access clamps loose.