SiNfidelity

Well I've tried a bunch of stuff and have now started paying mechanic for help. Grr

Hi.
My 8 won't idle since puttin in a secondhand motor. Have tried all usual suspects inc compression, maf, vac lines, throttle body, ess, plugs, engine loom, coils, and leads.
A mechanic did a scan and noticed while Idling a fuel system fault message lit up right before the revs increased on their own then CL message (closed circuit we think) then car stalled. Each time it was consistent with same messages in relation to the car idle then stall.. We moved swapped out relays for circuit and fuel among other blue buggers but no fix or change.
Of interest is unplugging the maf creates stable idle?.

Wot u think I shld try next? Ecu, fuel pump.? I read the circuit relay sends power to fuel pump via a resistor in air pump.. Cld it be that the air pump or the resistor in said AP are faulty? The air pump is making a lot of noise when cold as I believe it should. Disconnecting the bottom plug on the air pUmp stalls the car so I'm guessing that's where the relay is sending its power before going to fuel pump?

It seems to run great thru the gears and rev range.. Every time I stop, so does the engine!

Car history, 200,000 km and the engine purchased has 60,000. I do not recall the fuel pump ever being replaced.oh yeh it's and 05 model car with 06 engine. Manual trans.

tpb7463

iTrader: (1)

Fuel injector wiring is a common mix up--double check it. And if it runs better with the MAF unplugged, I would suspect something is up with your grounding, or you have a leak in the fuel system.

SiNfidelity

Thanks, i will look at those options tho i don't think the injector wiring is the issue as the motor came with loom all still attached and had the bad idle. I then changed the loom to my old engines loom and noticed you'd be hard pressed to mix up the order as they are all cut to specific lengths.

When u say leak in fuel system, do u mean air could be getting in to the line or leaking fuel?

Today i tested power at idle from the wire leaving the fuel pump resistor on its way back to the pump and power did not decrease until after the idle started fluctuating at which time it dropped to 9v probably due to less power being created due to almost stalling. So yet another couple things to rule out for certain. Resistor and relays. grrrrrr

Of note, when i put the multimeter on it today the damn thing wouldn't stall!! i tried it 15min later and same deal so i let it cool for a half hr or so then tried again at which time the problem started again. Don't get me wrong this problem is present 98% of the time.

So some more background, the car blew and engine and was off the road for about 3-4months before i popped in second hand motor. So the only things i haven't changed on the engine so far for elimination purposes would be injectors, port valve motor and the intake manifold.

revivo73

If unplugging the MAF sensor makes the idle proper, and if MAF sensor is ok, then ECU might be bad. My guess.

SiNfidelity

Yes it's starting to lean in that direction.

Something i've just recalled, and i feel a little "blonde" for not thinking bout this sooner. 3-4months ago my last engine died as a result of a failed bearing i was told, this on a rebuilt and balanced engine with 50k km on the clock. mmmm, this in itself was quite traumatic at the time as this rebuild had cost me $7000au BUT here's the clincher- THE CAR WAS STALLING!! i thought at the time is was a dead coil or coils but my mechanics soon discarded that in favour of a damaged engine. Now i'm racking my brain to recall how bad the stall issue was and hopefully in the next 12hrs i'll figure it out. Of course now i'm starting to doubt my mechanics (ex) were being very truthful. Yes they showed me a damaged eccentric shaft and 1 rotor BUT the housing are not damaged so how would i know for sure. The plot thickens.

tpb7463

iTrader: (1)

Hold on, "blew up". You did clean out all of the oiling system, correct? Catastrophic failure of a seal where it scores the housings and leaves shards of metal everywhere will remain present in your oil coolers. I didn't see any mention of it, just making sure.

As to the fuel leak, I mostly mean air. I would point towards the EVAP system, particularly around the charcoal canister--air can sometimes sneak in that way. However, if there's no CEL, just double check the fuel system pressure and move on to something else. Fuel injector health is something to check as well.

The ECU could definitely be the culprit. Stalling on a battery-change or engine swap can disappear after the ECU "re-learns" the fuel trims. But if you've been driving it, and the stalling hasn't gotten any better, and if/when you can rule out a bad MAF sensor, that'd be my next guess. But as I mentioned before, electronics can act as failed if your grounding isn't solid--start scrubbing those contact points.

SiNfidelity

Ill have to check on that. I just assumed the mechanics did that when the pulled the engine down. It wasn't a seal but bearing failure. Damaged the shaft and one rotor, so the damage wasn't extensive. That's my point tho, there seemed to be nothing wrong with it except stall issue. I took it to them thinking coils maybe and next thing they say broken engine. I put second hand motor in and guess wot, still has stall issue. Over diagnosed one might think. Ill be calling them within an hr to get things straight

SiNfidelity

Something to mention is it also sometimes "hunts" for idle as in fluctuates from 800-1500. It seems to happen at certain temps. Like i drove this morn very mild winter for the first 20-30mins it was a bitch, stalling every stop unless i kept the pedal pushed and even then it would fluctuate. So i'd hold revs about 1800-2000 and the needle would still be up and down.
Then i was sitting in a parking lot on my ph and it didn't stall for about 10-15min and was fairly stable at 800rpm. It then began hunting again and stalled. I drove home and decided to run some more electrical tests with the multi meter, and do u think i could get it to stall??? NO!! grrr. Usually a jab of pedal 4-6000rpm and stall but not today. So i turned it off, let it cool for 30mins and sure enough the problem is back.
The car feels great thru the rev range and at certain temps the idle settles a bit for awhile 20min-30min but most of the time at least for the 1st 30min of driving its hell. i did shoot a vid of the idle doing its thing before stall. i may UL it if that helps.

SiNfidelity

ive finally booked it into Mazda for diagnostics next week. I also purchased a second hand ecu so depending on wot Mazda find they may install ECU too.

Something else ive noticed and very very rare, i lose POWER like 30% at least (feels like dropping a rotor or like the old days when a secondary wouldn't open) from take off till EXACTLY 6500rpm at which time it kicks like a little turbo and in consistently 6500 every gear!! WEIRD!!! Not sure if its temp related. This car is driving me CRAZY
So to clarify- crap power till exactly 6500 then kicks like back to normal.

SiNfidelity

UPDATE for bad idle and stalling

NO one cld find my problem, but finally I found it.. It's taken me 3months.
NEUTRAL SENSOR SWITCH at top of gearbox!,,!
Tested it and failed, swapped it out and reset ECU AND PRESTO. TOOK A few drive cycles and about 200kms for it to find its tune again but now it's purr-fect

alnielsen

iTrader: (4)

When the neutral sensor went on my car, the idle wasn't stable. But, it didn't stall or loose power.

Karack

it probably could create that scenario if the KAM wasn't reset after the engine install. 20 brake pedal stomp or a manual reset inside the ECU with a scanner to relearn the adaptive memories and e-shaft profile as well then the idle needs to be learned by letting it idle without interaction for 15 minutes.

sometimes this needs to be redone after running an engine initially for 15 minutes - 1 hour. remans and replacement engines will take some time to settle themselves into a car depending on how long they have been sitting/rebuild procedures performed.

SiNfidelity

The loss of power was a solenoid issue for secondary intake.

SiNfidelity

I've lost count of how many resets i've done hehe.

I've had the idle problem for approx 15000 km, so after replacing the faulty switch it had a miss at 4k-5krpm every gear under load and would still occasionally stall. A couple of drive cycles later it started running almost perfect, so i gather the ECU needed some time to sort retune.

SiNfidelity

At my wits end with this stupid Rene
There are ghosts in my car I swear, can't wait to get the 20b in her.
So she ran great for about 200kms or so then today I had a stall then very rough idle, I mean not the same rough like before. Black smoke from tail pipes.. Running rich I guess, so then I hit the highway and she was misfiring god awful 4k-5k rpm and back firing/popping for about 60km. I cleaned oxygen sensors, checked wires, rotated coil packs with some spares I have (secondhand)..

Anyway, took for another drive , no more misfire but stalling and hunting again!! Fark!!!!!

Ghosts???

nycgps

iTrader: (1)

idling hunting?

have u check the purge solenoid ? that effects idle.

SiNfidelity

Yes I swapped it out and no difference. I think ill book it in to swap out ecu with the spare I bought. Maybe the ecu is shot. I'm running out of options. It's a rocket through all the rev range but just won't frigging idle. It just seems to choke. Have to hold the revs at 2-3k to keep it goin. At 2k it'll still hunt. Once it warms after maybe 30min of driving it def gets better and stalls less.

nycgps

iTrader: (1)

u mean the idle just jumps around below 2K ?

what u have u changed so far? are they all new parts? list it out.

and mind u, all USDM Rx-8 has immobilzer in ECU, so unless you have Dealership computers, u can't just swap the ECU, cuz the car will not even start.

skc

Check the air filter condition and leaks between TB and MAF.

Who did your engine rebuild?

SiNfidelity

hence why i said i'll book it in for the ecu change.

wot haven't i changed or tried would be easier to tell.

Have changed and tested and swapped out below. I had a whole spare engine and my GF also has rx8 so its not too difficult for me to swap **** out.

MAF twice swapped and cleaned multiple times
smoke test performed by MaZfix
cleaned and swapped out CAS
both oxy sensors
cat convertor
checked power to fuel pump
purge solenoid
3 solenoids on UIM (ssv, air, vdi)
neutral and reverse switch (which i thought fixed the issue as it ran perfect for two days approx 200km) It never ran this good before.
New coils
new plugs
new leads
checked by swapping out all the relays under the hood.
water temp sensor.
the whole engine loom (mainly cos my cruise wouldn't work with the new engines loom for some weird reason) even tho every single wire and plug was identical.
compression test done too.
oh and i swapped the whole UIM too.

SiNfidelity

second hand motor. low kms.

we had it compression tested and a few mechanics have driven it and claim the power is good thru the rev range. Just won't damn idle!!

SiNfidelity

what about the SSV? can it cause stall and bad idle hunting etc.

sorry i meant "emission intake manifold apv actuator". This is one thing i have not tried changing, mainly cos it looks like a bitch to do.

nycgps

iTrader: (1)

it sounds like some fuel related issue.

lemme ask you, how did u do ur injectors when you swap your engines ? you said u're sure u did the wiring right, you might wanna recheck that.

and u might wanna make sure there is no air leak at the injectors, when that happens, idle goes to **** but mid-high rpm will be fine, and of course check and make sure the primary injectors are actually working as it should.

04Green

iTrader: (1)

SSV is the only thing left. There is a good video on this site on how to do it. I posted some lessons learned to the end of the thread. It has a sensor that detects if it opens correctly, and will throw a code if it does not. It does NOT have a sensor that says it closed correctly. This will let air through where the ECU does not think air is going through (no big deal), but if enough goes through, a lot less is going through the passages with the firing fuel injectors, and that will screw up the mixture, which the ECU will try to fix based on the O2 sensor, which it cannot, because it expects the SSV to be closed.

Best I got.

Carb cleaner works a lot better than mineral spirits to clean it. And, I do remember that it idled a lot better after I cleaned it, and awful lot better.

SiNfidelity

A BIG thanks for ur advice so far.

Yeh i believe the injectors cld also be the cause tho not from being connected wrong but maybe from air leaks. The loom can only really be connected one way as they plugs really just reach where they are needed. I did swap out the loom after i discovered the idle issue and my old loom had hardened considerably making it quite obvious where they needed to be connected.

So i'm down to APV, injectors not working properly, air leak at injectors and ECU swap.

I'm swapping to a 20b very soon but i still need this thing to idle properly 1. to pre sell the 13b- i wanna take peeps for test drives. 2. if it is a sensor or ecu issue then it may be present after the 20b conversion as i will be using a lot of the same **** from the 13b set up and existing in the rx8 itself.