hey i just bought an rx8 with a bad engine i replaced the engine and it has good compression it was r1 115 r2 107 and i dont know why it wont idle its very bad ive look at everything the last thing i think is vacuum i looked at every line and i also make a home made smoke machine worked pretty good but i couldn't find a leak neutral switch is good it i replaced the ess i gave it plenty time to learn fuel trim the injectors are in the correct location replace plugs coils and wires i looked over every little thing and i can find nothing im going to put a picture of the graphs at idle before it starts to hunthey i just bought an rx8 with a bad engine i replaced the engine and it has good compression it was r1 115 r2 107 and i dont know why it wont idle its very bad ive look at everything the last thing i think is vacuum i looked at every line and i also make a home made smoke machine worked pretty good but i couldn't find a leak neutral switch is good it i replaced the ess i gave it plenty time to learn fuel trim the injectors are in the correct location i looked over every little thing and i can find nothing ima going to put a picture of the graphs at idle before it starts to hunt

the left side of the graph is where i just started the car and the idle is smooth but then the idle starts hunting if you look on the left side of the page it shows you the RPM and the G/s the maf is reading

 

Since you mentioned that you replaced the engine did you try the 20 bream stomp ECU reset n relearning procedure usually if it stalls after a battery disconnect or smt for no reason tht fixes it.. you said u gave time to relearn fuel trims but trying this as a start wont hurt ig .
you can find videos abt it on utube jus type rx8 ecu reset

 

yea i did it will idle half way for that first drive after the break stomp and then it will not idle the next morning

 

might sound a bit wierd but since you checked everything and everything looks fine i suggest giving a look at the barometric sensor when it goes kaput it thinks we r on top on mount everest inseat of whtever elevation u are at n this can happen. Not guaranteed but you can try to read the baro sensor output throught an obd2.. a bad baro will definitely stall the car..

its located above the ECU , below the air pumo for the cat

 

alright thanks ill look in to it

 

looking further into it, it looks like its reading accurately not sure what else it could be tried almost everything now but i think that 4.7g/s is quite low no?

 

ok now looking in to it i belive i have a fuel issue because when the secondary injectors turn off the car begins to lean out i will put the picture below


the yellow is the AFR and the Orange is the Engine RPM dose anyone know if this is normal or not

 

ok i know ive been posting alot here but i noticed with the MAF sensor unplugged that the car idles perfectly but obviously drives horribly please help im very lost here

 

it sounds like when its in open loop it has wrong info from a sensor, MAF, O2, other. when you unplug the MAF it goes back to a base map or "closed Loop" other words ignores other sensors to adjust fuel. Any more info would help.

 

what info would you like? the MAF at idle is intaking around 4.7g/s at 830 RPM on idle it seems im getting anywhere between 11-14 AFR the Baro looks good the neutral sensor is reading correctly my LTFT is around -5 at idle same with the STFT not sure what else to look in to

 

That's the opposite of what open loop means. Open loop = ignoring O2 sensor and using base map + fuel trims. The base map is based on airflow, so there's no scenario where it's ignoring the MAF.

If you're getting -5 LTFT and also low airflow at idle, it's trimming back fuel, not adding as it should. So I think you have your injectors reversed. It's a common mistake when installing engines. Go back over the injector set up and the wiring to them.

 

I did that at first when I installed the engine but a few months ago I went back and swapped them and I'm sure they are in the right position now do you think it could be clogged because that's what I'm thinking not sure what else it could be

 

Do you have a aftermarket intake by chance? looks like its pulling fuel out and running lean, (thinking its rich but really its not) any misfires? how do the plugs look? im assuming compression ok when warm. Does it do this cold as well? I would mess around with that MAF sensor more. Piping or cleaning, or maybe faulty. Hunting for a smooth idle is a symptom of vacuum leak or sensor issue. from the data you have -5 LTFT is typical value BUT it will add it eventually +5 ~ if healthy. If its pulling fuel all the time Id suspect that MAF... anyone else can chime in here....

 

No I have a stock intake the screen is still there i replaced the MAF when cold it runs 11 AFR seems pretty rich warm can be anywhere from 11-14 AFR no misfires the whole ignition system is new cleaned plugs a week ago good compression when cold it will idle just fine until it warms up i have a P0038 and a secondary injection pump code that's all of the information that i can think of i might clean the MAF on more time not sure what else to do

 

ok so when I'm cruising the LTFT is around -13 but when i get on the throttle it goes to -9 my STFT (primary) when cruising is around -8 and when at full throttle it is at 0 my STFT (secondary) is at 0.5 and looks to be very choppy having a bunch of random jumps to 1 through -1 and at full throttle it is at -2.1 just trying to give more information to get this figured out also at low RPM driving it is very hesitant and jerky

 

Yes you are correct about the open closed loop. my mistake. Switch that around. My point was still as follows: If injectors are correctly installed and MAF is reading correctly then if the ECU goes into "open loop" (a code for MAF Sensor when you unplug it) and idles better, then more fuel is being added (runs better) not looking at O2 sensor. So it seems like its starving for fuel. Why? The ECU thinks its rich so its pulling fuel OR MAF is not monitoring all the air. Is there a possibility its pulling air from a torn intake rubber after the MAF? Reading low flow on the MAF will lean it out for sure. That is un-metered air going in. Granted this is just the internet and real situations can change everything.

 

Hey food for thought, That P0038 is a Problem with the Heated Oxygen sensor circuit. Test to see if you have 12v to the heater on the sensor. If you do then The ECU does not see a current draw on that wire and will hit the check engine light. WHICH might be the root cause of all this... If the ECU looks at the oxygen sensor and sees a false rich condition it will pull fuel out and starve the engine. (replace upstream O2 sensor) Also side note is you're motor working for the air injection system? The secondary air injection system is based on the downstream o2 sensor, when you first start the 8 it looks to see if the signal from the DOWNSTREAM o2 sensor goes at a lower mV signal (signifying a lean mixture from that air pump to help "Light of" the catalytic converter. If you still have a cat.. If you want that code gone i have a solution with the air pump deleted. Let me know...

 

could it be the down stream 02 sensor i dont think it could and the issue is in the wiring of the 02 senor so i would have to look that over but i dont think it is but i will take a look i also replaced the intake boot because it was torn it might be a vaccum leak but i didnt see any smoke when i smoke tested it im not sure

 

The downstream O2 is narrowband only there for checking cat health. It's not the problem, although obviously if you have a cat, you want the sensor fixed. Fuel trims especially STFT will do all kinds of things while driving, they're not really useful information. LTFT has basically 3 bands: idle, midrange and upper range. I don't know exactly where the boundaries are, but idle is the most sensitive so let's focus on that. A cracked book certainly wasn't helping, is it any better since?
11 AFR while cold is normal, it's cold start enrichment. When warmed up it should be able to maintain 14.

Open loop has to do with the O2 sensor, not MAF.

Your MAF is not measuring enough air for the rpm you're idling at, so either air is getting in somewhere else, or the MAF is faulty. But further, the fuel is getting trimmed to 5% less air than the MAF is measuring, which is the weird part. So the question is, what AFR is it reading? If it's 14, you're injecting way too much fuel to begin with (like if the injector wires were swapped). If it's rich, or unstable, your front O2 is lying, although you would have a code for that, usually. You can replace the MAF if you want, but I don't think it's that.
It could also be the baro sensor which lives on your air pump, normally. It has an open port to atmosphere, which some people have mistakenly connected to vacuum, leading to similar symptoms

 

OK gotcha, I agree its not the down stream o2 sensor, that is not responsible for engine fuel adjustment. Think of it this way its the manufacturers way to include emissions checks to make sure CAT is working. Lets say you had a vacuum leak, well IF the upstream O2 sensor was working correctly then you should see the LTFT adding fuel and depending on the size of the intake leak +5-10~. When a heated oxygen sensor goes bad it will read BUT there is no heating element so it will read a rich condition 99.9% of the time. Question when you reset the Check engine light does that code come back? If it does then I would bet that O2 sensor is the culprit. Ill put it this way If you have a known code that keeps coming back with the Upstream O2 sensor and keep searching for other reasons you might be wasting money with parts you might not need in the first place. Until that P0038 clears, either clearing it with scanner and it stays clear or replace that O2 sensor. I wouldn't move on... I fear well all go on a wild goose chase. Just want to get this sucker whipped. I enjoy the diag process thanks LOKI as well for helping.

 

P0038 is specifically the rear O2 (Bank 1, Sensor 2) Are there other codes for the upstream O2 as well?

 

no its just for the down stream but i noticed its in closed loop fault most of the time when cruising it goes in to closed loop for a few seconds and goes back after taking off the battery it goes in to open loop fault and idles almost perfectly not sure what's causing this im going to try a different front o2 sensor and no there are no other codes thanks for all the help guys i dont know what i would do with out the help my afr is reading around 11 during wot and 14 at idle cruising is around 13 and i check my baro sensor is reading correctly i got a replacement maf but it doesnt look to good quality im going to stick to oem next time i got it from oreilys i tried it and it made no difference even

 

i think it is the front o2 sensor because sometimes its 11 afr when in open loop and goes in to closed loop and dies

 

Gotcha, hey I had mine go out before, I think i dropped it accidentally. Let us know what it does after. As far as the MAF i agree sometimes a aftermarket one will be cheap and cause problems but one thing at a time.

 

O2 sensors don't really give consistently wrong readings when they die, they give no readings at all or jump all over the place randomly. So I still think it's just reversed injector wires/positions, but I suppose you can unplug the front O2 and see pretty quickly.