When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
A complete newbie attempts to fix P0171/P2096/P2270
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... *****...
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
Accelerating 1 Accelerating 2 Constant speed Stall at idle 1 Stall at idle 2
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 - 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 - 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... (Is that the WBO2 sensor dannobre?)
SORTED!
Turns out the MAF was the source of all my engine related issues but was throwing the wrong codes
Gold contacts at the back of the head unit needed tightening and that's fixed now too
There is something going on in the exhaust. I run both O2 sensors in a straight pipe and only code I get is P0420. I would suspect an issue with both of your O2 sensors. May need to replace head unit if your wiring is good. I’m having the same issue and need to replace mine.
There is something going on in the exhaust. I run both O2 sensors in a straight pipe and only code I get is P0420. I would suspect an issue with both of your O2 sensors. May need to replace head unit if your wiring is good. I’m having the same issue and need to replace mine.
I did have a go at cleaning the MAF with some methylated spirits but after googling a bit more apparently they can leave some residue so I'm waiting for some MAF cleaners to arrive. While it's drying I'll give the car a diagnostic drive without the MAF and clear the codes and see if anything pops up still.
Wideband O2 sensor? Not a clue. The car was first registered in 2006, I brought it in Feb 2020. I'm the 8th owner
The O2 sensors fail... I wouldn't chase my tail looking for a problem when you don't know if the sensor is giving you good readings or not.
I would replace the sensor and see what happens after that.
04-14-2020, 11:41 PM
