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2007 MT
The car has a new Mazda reman that I've been driving for about 300miles now, but this issue has persisted mostly unchanged since the swap. I bought the car with a blown engine and mostly disassembled and I had to go off of wiring diagrams to get everything put back together so I'm not sure if it's the car or the engine at fault.
The engine is stock, the only things that are modified are sohn adapter, BHR coils, BHR midpipe w/ cat and RB catback. I don't know much about the history of the car, it did have some mods that I've undone and put back to stock (K&N intake and eBay headers).
The issue presents as a surging/hunting idle and a stall on clutch in stops. The car has no issues starting cold or hot and runs very well if it is not at idle.
I've been troubleshooting with the help of a local mechanic, nobody in my area does a lot of stuff with rotaries so it's been tough. The dealership was useless.
There are no codes at this time, previously I have replaced the MAF, front and rear o2, my mechanic has tested the coils and plugs (receiving spark to all four in the correct order), the injectors (both position and operation), the fuel pressure is correct, there are no vacuum leaks (smoked the bay and found nothing). I've done the fuel trim reset by leaving the battery undone, I've done the 20 pedal stomp to clear the ESS profile, and while they seem to help the issue soon returns.
We are completely at a loss, the only thing we can see is that the ECU thinks that the car is running rich and is pulling all the fuel that it is allowed to. I'm not sure if this is the problem or a symptom of the problem. If you let it sit at idle and get up to temp, the surging will begin when the ECU goes into closed loop mode, (it will not have issues when it's cold and running in open-loop mode).
literally anything yall can think of to check would be appreciated, I've been banging my head against this for 6 months.
I found a thread that details a similar issue. Did you try any of the things suggested in this thread? Possible it could be a vacuum leak, dirty MAF/ESS sensor or something relatively easy to diagnose.
Thanks for the suggestions, I checked the neutral switch and clutch position switch both are working fine and the ecu sees them. The cat is new from BHR as the car previously had a de-cat (the cat smashed out of the factory mid pipe).
The MAF has been cleaned and replaced twice and I reading well, and the engine bay has been smoked multiple times, so no vaccum leaks. I cleaned the ESS sensor and did the profile reset and the issue persisted, so I tried replacing that sensor and nothing changed.
Again appreciate the suggestions, keep em coming!
It's easy to mix up injector wiring, the wires are yellow and beige. If you wired secondaries in the primary position and vice versa, this is among the symptoms you'd find. The car would actually be overfueling and doing its best to compensate because the secondaries weren't designed for idle.
The other thing is do you have the mesh screens in the intake system before the MAF? They tend to get lost when swapping intakes, but in the stock system (any system?) they're important to keep the MAF reading correctly.
Hi from my last thread on this issue lol
The screen is in the intake before the MAF and that looks correct.
I swear I have the injectors right, I have them in the rails according to every diagram I could find and I used a multimeter to check which connector should be where based on the wiring diagrams of the PCM.
I also had my mechanic check my work and he tested the injectors himself. IDK if there are different PCM pinouts and I used the wrong one.
I don't have access to the proper compression tester otherwise I would. I don't have any of the other issues associated with low compression. It will start right back up at the first crank after it dies and no other issues with hot starting.
Last edited by SonofaMitch; 10-18-2020 at 12:03 AM.
Reason: typo
I don't have access to the proper compression tester otherwise I would. I don't have any of the other issues associated with low compression. It will start right back up at the first crank after it dies and no other issues with hot starting.
Really strange, by all accounts, this car should be running well. Have you done the reset on the ECU? Commonly known as the 20 brake pedal stomp. This thread shows how to reset both the KAM and NVRAM:
I have done both resets and they don't really help. I know there's got to be something going wrong with the fueling because it does really smell rich, but I just can't find it.
I have done both resets and they don't really help. I know there's got to be something going wrong with the fueling because it does really smell rich, but I just can't find it.
When was the last time spark plugs and wires were changed out? Weak plugs and wires sometimes don't trigger a CEL but can be a symptom of running rich. You have BHR coils so I doubt those are the issue.
You really should get an OBD2 reader. You'll want one to monitor the coolant temp unless you install gauges. Logging what the computer sees in real time is invaluable when trying to diagnose problems. Learning what the values of fuel trims, maf, 02 sensors etc should be under certain conditions is a learning curve though. Watch videos of mechanics using scanners and you can pickup a fair bit of knowledge, doesn't have to be rotary engine based necessarily.
You could try un-plugging the barometric sensor temporarily and see if that makes any difference. But this is all guesswork. Goodluck.
Plugs and wires were both new with the coils and I do seem to be getting strong spark with a spark tester.
I do have an obd reader that I've been pulling data from, but I haven't looked at the barometric sensor so ill take a look at that.
One thing to check is the eccentric shaft position sensor if you haven't already. Sometimes it can even have issues from just having crud on it.
If the car can drive fine have you recently tried going above 6-7k rpm? To see if the fuel pump is starting to go? Concept is that it may be starting to fail as everything heats up.
Which fuel injector diagram did you use? When I had issues with mine when my father was helping me, the diagram he used from a forum page was actually different than what I used. I had to follow this one making sure not to mess up the tan, yellow, white tapes (really mazda, who did this......nearly all the same color tape and multiple duplicate wire color combos????)
Doubtful that it is the bhr coils, but if you have the stock coils you can rule one of the bhr's somehow being bad by swapping the stock coils back on. Again concept is here that a bad coil could start having issues as the engine sits at temp> bad spark> bad O2 read> ecu freak out.
Check the voltage on the battery during this idle searching, could potentially be drops from things like heat/ ac/ secondary air pump.
Considering you are seeing the car lean out, checking the front O2 sensor wouldn't be a bad thing to do. The secondary O2 sensor should just be for emissions....although say if you hear the secondary air pump running for whatever reason just sitting at idle I suppose that could be a sign that the cat is having issues.
Do you premix with the sohn kit? I had issues with one of my engines where I kept fouling plugs due to premixing>>bad idle. Its also easy enough to just check the plugs. (this was my pre-rebuild engine that had many other problems adding to this issue) Cat could also be taking a hit if you are premixing with the sohn as well.
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Personally I'd recommend getting a compression tester kit even if your engine is "new", it sucks, but so does blowing money randomly on potentially O2 sensor + Eccentric shaft sensor + injectors+ fuel pump+ relays+ solenoids+ cat (or res midpipe)+ maf sensor+ Air filter+ plugs + 10mm sockets when you end up losing them.
I wish I told myself 5 years ago before struggling through college keeping an engine under 85psi running through multiple winters/summers in New England.
Would love to see a vid of it idle then die out on its own and start within 30s
The car revs out to redline without stumbling, and fuel pressure tested within spec so I'm confident the pump is ok.
I don't have the OEM coils, the when I bought the car it was in pieces (got a killer deal lmao)
Front O2 has been changed during the rebuild and once after and the issue persisted, it is giving data and the AFR is reading within reason.
I did premix the first tank of gas and then didn't premix the second. I did check the plugs and they were black from carbon and smelled fuely, but nothing changed when I swapped them.
I only have a video from this summer of the car dying while idling, but the symptoms are slightly different and I've fixed a few things since then.
10-16-2020, 12:08 PM
