A complete newbie attempts to fix P0171 (pending codes P2096/P2270)

[Autolysic]

First off, sorry for posting here, it's the only place I seem to be able to post too...

I'm not trained mechanically at all, in fact this is the first car I've worked on beyond changing a flat tyre, changed and oil filter once, jump starting a car and changing a dead battery.

Any tools I'm using I'm buying as I need them or I find them in a random tool box in my flat (who needs 5 hammers that are all the same size!?)

Recently brought my first RX8 (have loved them since I was about 16), was originally a cat C write off (front end panel damage) that a rotary specialist brought from a guy who was turning it into a track car (has sat in storage for 4 years before being refurbed)

what has been done to the car:
They put on a styling kit and carbon fibre hood as a fix to the panel damage and have refurbished the engine (it's currently under warranty).
Went to pick the car up but was waved off for a week, there was an oil leak apparently caused by a nicked o ring.
Decatted
Apparently has D585 coils + HT leads, looks like the images I've seen too
Got in the car and noticed CEL was on, asked and the guy said that's because of the decat and will happily remap the ECU to remove the CEL when the engine has had it's 1000 mile shake down, get's it's oil change and a new oil filter (and I can go above 4k revs) Made a note to get an OBDII scanner...
First 100 miles of me owning the car oil lines to the coolers broke (instantly pulled over and got towed to the garage). They picked up the car, replaced the lines and returned the car free of charge (100 mile round trip) the guy said the car was fine.
Has an AEM induction kit.
it's a PZ but has a 5 speed transmission for...some... reason? I hear they are supposed to be stronger (could have been damaged in the crash?) - This being said the car lurches in 2nd (around 20-25 mph) and continues bouncing unless I increase or decrease the throttle and when the car is hot it sometimes grinds in 3rd (worn syncros?)
Has cabin fire suppression system (tank in front passengers foot well)
Head unit kill switch
Engine kill switch
Emergency engine kill switch (had to work out what this was a garage didn't know...)
Push to start button (never worked)
External engine kill switch and fire suppression system (disconnected)

OBDII scanner arrives and CEL says P0171 - bank 1 running too lean. I think nothing of it...
I get 130 miles to a tank (London driving) and think to myself "you were warned 8's a thirsty..." continue to drive and the mpg slowly improves, getting 150 to a tank and thinking that's more in line with what I've read on the forums.

Issue 1: Head unit stops responding slowly and intermittently...then completely dead (still lights up)

Attempt 1:
ex-mechanic father suspected a dry joint so:
Removed all clear topped J-socket under bonnet fuses and gave them and their contacts a spray in WD40, checked for any blown fuses
Removed all cabin fuses, check for any blown (none), scrubbed them shiny and WD40'd them

While under the hood I noticed my oil level was just above half so I chucked 250ml in and then it read full (both done while engine was hot and allowed to stand for 10 mins after stopping and after adding oil). Maybe over filled a little? This dipstick is a bit ****...or I am one of the two.

Outcome:
Issue 1: Head unit still dead
Issue 2: Now have a lumpy idle runs fine when driving
Issue 3: Engine drops revs really slowly when foot taken off the throttle and stalls when clutch is depressed
Issue 4: DSC light permanently on
Issue 5: Head unit kill switch light now flickers

Well... balls...

Attempt 2
Issue 1: Removed head unit and checked all connections (turns out I had a tiny 11mm ratchet that JUST reached, I'm sure people had a good laugh looking at the weird angles I had to get myself into)
Issue 2: 20 brake stomp to tell ECU to reset and left for 20 minutes to "learn"
Issue 3: Code P0171 is telling me the engine is running too lean and suggests "vacuum leak/ injector faulty/ MAF faulty" Removed and cleaned Mass Air Flow sensor with mineral methylated spirits
Issue 4: Turned the wheel full lock left and then full lock right
Issue 5: Re-soldered head unit kill switch, engine kill switch and push to start (had a lose bare wire!?)

Outcome:
Issue 1: Head unit fixed! sometimes needs a firm press just below the CD in (suspect it's moving away from the contacts), I'm fine with this fix, mostly listen to the engine anyways.
Issue 2: Idle is smoother but not near the 800-850 revs but hunts a small amount compared to before...
Issue 3: No change ECU now throwing up codes P2096 along with the P0171
Issue 4: DSC reset, no further issues!
Issue 5: Head unit kill switch light no longer flickering!

Attempt 3:
Issue 2: I find some threads backing the idea that ECU needs more than just 20 minutes to relearn at idle and needs about 100 miles or so sometimes. I park this issue as I currently don't have a solid 2+ hours to do this in one stretch.
Issue 3: Code P0171 is telling me the engine is running too lean and suggests "vacuum leak/ injector faulty/ MAF faulty" so when the engine is up to temperature I spray WD40 around the vacuum pipes and engine while listening for an increase is revs and looking at the rev counter on the phone (OBDII is Bluetooth), no change. I spray soapy water over all the hoses and connections to double check (and remove any excess WD40, don't want the rubber to perish), again no change suggesting there is no vacuum leak.

OBDII shows Air Fuel Ratio commanded is 14.6:1 but measured is 15.6:1 When driving with the throttled pressed the commanded and measured match, take my foot off the throttle and the measured jumps up again...

took the car for a diagnostic drive with OBDII graphing: Absolute throttle position/Air Fuel Ratio (commanded)/ Air Fuel Ratio (Measured)/ Engine load/ Engine load (absolute) - results below

So the AFR commanded and measured disconnect from each other during acceleration and just before the engine stalls at idle. Additionally when the car is left out of gear measured AFR reads the max reading of 22:1

Outcome:
Issue 2: No change
Issue 3: No change
Issue 5: Head unit light flickering again - I have bigger fish to fry...

Attempt 4:
Issue 2: Take the car for what turns out to be a 3 hour drive to Brighton and back (104 mile round trip), I don't even get out the car. Engine runs and idles fine...apart from issue 3.
Issue 3: During 100 mile drive I notice that if I blip the throttle the engine doesn't stall. Along the way I hear a high pitched pinging noise when I accelerate in 4th and 5th at high speeds I pull over and run a scan on the fault codes fearing some pinging/knock and get a 3rd fault code P2270 - 02 sensor biased or stuck lean, bank 1, sensor 2 (Wiring, H025, fuel pressure, injectors, intake leak)
(the noise turns out to be a empty can of coke rattling around). I switch the OBDII to show me air status and fuel status in real time. When I depress the clutch the car switches from closed loop to open loop if I leave the car in open loop then the engine will stall 4 out of 5 times. If I blip the throttle the car switches back to closed loop and the engine idles fine. I also notice that I've done 180 miles and have over half a tank left...WHAT!?
I get home and try not to die a little inside.

Outcome:
Issue 2: Idling fine
Issue 3: Three fault codes now
P0171 - bank 1 running too lean (vacuum leak/ injector faulty/ MAF faulty) - Ordered some actual MAF cleaner, will give it a super clean, leave the MAF to dry and give the car a diagnostic run around after clearing the codes, see if the MAF really is the issue. Forums also suggest aftermarket intakes can cause this code. (at this stage I'm hoping my full oil level is causing some to be sucked into the intake and fouling the sensor, if so I can ring up some kind of suction tube to remove the excess)

P2096 (pending) - post catalyst fuel trim system too lean, bank 1 (Cat sensor detecting too lean) - this is interesting as the car doesn't have a cat so... triggered by dirty/faulty MAF? If removed/cleaned MAF still triggers this then I'll go buy some stands and a jack (took me 10 minutes to jack one side up using the emergency scissor stand and tow bolt when I cleaned the under tray of oil to check for further oil leaks, first time under a car, a low one at that, gave the car the jiggle test before getting under it, absolutely terrified it would fall and crush me)

P2270 (pending) - 02 sensor biased or stuck lean, bank 1, sensor 2. (Wiring, H025, fuel pressure, injectors, intake leak) - Is this the sensor after the cat? Not sure if I even have a sensor there or if the decat is just a straight pipe - Stands and jack seem to be calling my name

Issue 5: Head unit light flickering again - Could this be indicating an electrical fault that is also affecting the O2 sensors? hmm...

Attempt 5:
Issue 3: P0171 - bank 1 running too lean (vacuum leak/ injector faulty/ MAF faulty) MAF sensor cleaner arrived, checked reading before (3.8 g/s at idle), sprayed it down for a good 5 seconds, waited another 5 and sprayed again, repeated about 15 times. Left to dry for 20 minutes and checked there was no wetness. MAF reading afterwards (still 3.8 g/s at idle).
Took the car for a diagnostic spin. Pending codes P0171 and P2270 still. Engine still stalling when pulling to a stop in neutral (fuel system switches from closed to open loop, blipping the throttle keeps it in closed loop and the engine doesn't stall)
Torque does now and then throw up under fuel status "closed loop 1 O2 sensor (fault).
STFT1 sits at +25% most of the time and LTFT1 at +0.8% if that helps anyone

Issue 5: Head unit light flickering still (going to ignore now...)

Outcome:
Issue 3: Looking at replacing bank 1 O2 sensor 2 whatever that is...

I have spent ages looking through the forums before getting an RX8 I knew what I was getting into... I have some mechanical understanding from my father e.g. I could point at bits and roughly tell you what they are/where they go/approximately what they do and if you tell me what system the part is I could probably work out what it's job is.

My only experience is YouTube videos and forums so give me directions filled with acronyms and you'll lose me, e.g. had to google: AFR, DTC, WD, LTFT, STFT, MAF

Am I on the right track? Have I missed something obvious e.g. in the graphs? Should I grab other data? Am I likely to damage my car beyond economical repair by running it and attempting to fix it myself?

Any and all help welcome. I'll check and edit this before and after I attempt some work.

[GreySilver Beast]

Hi & to the RX-8OC


Please check out the EVENTS SECTION's for anything coming up soon in your area

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[BigPete]

First off who built the engine?
Any porting been done?
Have you changed the O2 sensors?

[shroom]

Hi and welcome, I'm sure someone will be around to offer some advice.

Sent from my SM-N960F using Tapatalk

[Shagrington]

Hi and Autolysic. Sorry I'm not one of the people here who has the technical and mechanical knowledge to be of much use to you, there are plenty here and I'm sure they will be along before too long (bigpete is here already ).

If you join the club you will gain access to all the workshop and technical manuals and the members areas of the forum you can't see a as guest - including the 'Ask The Spin Doctor' section where you can put your issues direct to our most experienced and knowledgeable members. In the meantime, if more of the right people don't see your post here you will be able to repeat your questions with a post in the 'RX-8 Discussion' section viewforum.php?f=6

[warpc0il]

If gearbox swapped from original 6-speed to 5-speed then they might not have reconnected the neutral switch, as it's in a different place and the loom doesn't line up.

This switch is used by the PCM to determine if the engine is or isn't "under load", in conjunction with the clutch switch.
With it disconnected, the PCM thinks that you're just sitting at the kerb reving the engine, rather than driving, despite the road speed input from the TCS/ABS unit - which could explain the strange behaviours.

[Will66]

P0171 codes are a pain to chase down. However it could be that the fuel pump is dying and the lean condition is down to it being unable to supply the required fuel pressure.

[350matt]

OK that data is all showing its very lean and this is borne out by getting the rather too good fuel economy you're getting

do not drive it again until this is resolved as it will all be getting very hot and may damage something

I suspect you have 1 of the injectors thats not opening and most likely is 1 of the 'yellows'
I'd say to take a look at the workshop manuals you have access to on here and then do a continuity test between the ECU connector and the injector plugs
as the wiring looms tend not to age well and the wire becomes brittle

and as will says its also worth checking fuel pressure
as you should get 4 bar with the engine running

[Autolysic]

First off who built the engine?
Any porting been done?
Have you changed the O2 sensors?

Warren Court Rotaries. Comes with a year guarantee.
Not been ported to my knowledge (doesn't sound like it either)
I have not changed the O2 sensors, working out which one(s) (advice welcomed!) and where to buy them (have cleaned the MAF which is getting 3.8 g/s before and after, reading does change)

[Autolysic]

If gearbox swapped from original 6-speed to 5-speed then they might not have reconnected the neutral switch, as it's in a different place and the loom doesn't line up.

This switch is used by the PCM to determine if the engine is or isn't "under load", in conjunction with the clutch switch.
With it disconnected, the PCM thinks that you're just sitting at the kerb reving the engine, rather than driving, despite the road speed input from the TCS/ABS unit - which could explain the strange behaviours.

I've had the CEL since I got the car and was told that it was due to the decat. Got a OBDII and it gave me P0171 and I looked no further. I never used to have these issues, they only started after I removed the fuses to try and clean them...

[Autolysic]

P0171 codes are a pain to chase down. However it could be that the fuel pump is dying and the lean condition is down to it being unable to supply the required fuel pressure.

The car revs fine and idles fine, when I press the clutch the fuel system goes from closed to open and that's when the engine stalls out. Fuel flow max figure I got at WOT was 730 cc/min

[Autolysic]

OK that data is all showing its very lean and this is borne out by getting the rather too good fuel economy you're getting

do not drive it again until this is resolved as it will all be getting very hot and may damage something

I suspect you have 1 of the injectors thats not opening and most likely is 1 of the 'yellows'
I'd say to take a look at the workshop manuals you have access to on here and then do a continuity test between the ECU connector and the injector plugs
as the wiring looms tend not to age well and the wire becomes brittle

and as will says its also worth checking fuel pressure
as you should get 4 bar with the engine running

I'll start educating myself on fuel injectors I suppose . How would I go about checking fuel pressure (will my Torque app be able to read it from the ECU?) When I put my foot to the floor apparently I get a fuel flow rate of 730 cc/min if that helps

[Will66]

P0171 codes are a pain to chase down. However it could be that the fuel pump is dying and the lean condition is down to it being unable to supply the required fuel pressure.

The car revs fine and idles fine, when I press the clutch the fuel system goes from closed to open and that's when the engine stalls out. Fuel flow max figure I got at WOT was 730 cc/min

730cc/min seems a little low, the 231 has four 420cc injectors and two 300cc injectors, I know they don't operate at maximum capacity as stock but the pump is flowing less than half their maximum capacity.

[Autolysic]

730cc/min seems a little low, the 231 has four 420cc injectors and two 300cc injectors, I know they don't operate at maximum capacity as stock but the pump is flowing less than half their maximum capacity.

I'm not supposed to go above 4k revs for the first 1k miles until the engine beds in, could that play a role?

What would you suggest I chase down first? WB02 sensor/ injectors/fuel pump?

[Will66]

I’d look at the pump since the injectors and the wide and are usually pretty bulletproof.

[350matt]

start with fuel pressure
this will show if the pump and reg are working correctly

a kit like this makes measuring the pressure easy as it has the same push fit connectors that are on the car

https://www.ebay.co.uk/itm/Universal-Fu ... SwPh5ZFSqe

I'd agree the injectors themselves rarely give issues but I've encountered 2 instances where the wiring loom has broken and given intermittent connection to an injector

[Davemitch]

Hows this progressing? Having similar issue myself with running lean and it's a total nightmare to track down!

[Autolysic]

Good news!

ALL ISSUES ARE FIXED!

Had the AEM intake off and a donor original put on and the engine issues went away. On a whim, switched the MAF sensors over and chucked the AEM back in and problem solved!

The gold press contacts at the back of the head unit needed tightening a bit and hey presto! Sorted also!

In the mean time I've also switched the black leather interior for the red and black.

[350matt]

So it was a dodgy MAF sensor ?

[Autolysic]

Yup, dodgy MAF sensor that also wan't reporting that it was dodgy so pretty much all the other O2 sensors were fine but were pinging codes because they were "wrong" compared to the MAF (also during all of this my throttle body had a breakfast of one of the meshes from the AEM induction kit).

[350matt]

possible that the MAF sensor has been damaged by the wayward mesh too?

[Autolysic]

The MAF looked fine, the hot wires have a plastic shroud protecting them and directing airflow, also issue occurred weeks after the mesh got swallowed.