Rich AFR and high negative STFT -25.12

[MPS-Joe]

Hi guys, I have recently been having a rich AFR at idle and STFT is pinned at -25.12. LTFT is fine and AFR when cruising is fine, this is only at idle. I know something has changed because AFR used to be bang on 14.7 at idle. Also get the occasional, very slight hesitation when accelerating, this morning I also got a DSC light and U2023 code, but it cleared straight away.

Car is fully bolted BNRS3.

Any insight is a bonus, I pulled the car apart earlier to check for boost/vac leaks or to see if I noticed anything abnormal, all looks fine.

[Pro60modman]

That's a rich idle. It's pulled 25% trying to fix it. Seems to me lIke a leaky injector if cruising and WOT are ok.

[mituc]

Check your oil and make sure you don't have an extra quart of gas, some stupid rubber o-ring inside it may fail over time and cause gas to spill into oil.

[MPS-Joe]

Yeh I meant to put rich, put lean for some reason, edited my post.

Surely if it was injector seals I would be getting lots of knock? Of which I get little to none.

Yeh I checked my oil, level hasn't risen and it doesn't smell of petrol.

[mituc]

Originally Posted by MPS-Joe Yeh I checked my oil, level hasn't risen and it doesn't smell of petrol.

That is very good, it means your HPFP is ok and your engine is using oil to lubricate, not gasoline.

Have you tried cleaning your MAF?

[MPS-Joe]

Originally Posted by mituc That is very good, it means your HPFP is ok and your engine is using oil to lubricate, not gasoline. Have you tried cleaning your MAF?

Yeh, cleaned the MAF, I have tried all the obvious/easy things including resetting the ECU, STFT goes straight to -25 at idle afterwards.

[Thor Hammer]

Have you done a boost leak check? Also check and or replace your evap purge valve. Its near the top of the fuel pump. But do a boost leak text first. A rich code indicates a leak between the turbo outlet and throttle body.

[MPS-Joe]

Originally Posted by Thor Hammer Have you done a boost leak check? Also check and or replace your evap purge valve. Its near the top of the fuel pump. But do a boost leak text first. A rich code indicates a leak between the turbo outlet and throttle body.

It's not the vapour purge valve, I've had that go in the past, so first thing I checked. I have not done a boost leak test, but I have double and triple checked everything from turbo to throttlebody. Surely if it was a boost leak it would show up at other conditions such as cruising and WOT, other than just idle?

[Pro60modman]

Originally Posted by MPS-Joe Yeh I meant to put rich, put lean for some reason, edited my post. Surely if it was injector seals I would be getting lots of knock? Of which I get little to none. Yeh I checked my oil, level hasn't risen and it doesn't smell of petrol.

I mean a leaky injector as in it is dripping fuel. It's not very common on the Mazdaspeed but very common on other direct injected cars.

[MPS-Joe]

Originally Posted by Pro60modman I mean a leaky injector as in it is dripping fuel. It's not very common on the Mazdaspeed but very common on other direct injected cars.

Nothing leaking out/nothing on the floor. I don't know what direction to go with this. Attached another pic of the AP at 70mph motorway cruise control on, trims and AFR bang on. Then a video of me pulling up to my drive and putting it into neutral where you can see the STFT creep down to -25.12, along with the AFR. Why on earth would it be pulling 25% fuel at idle, but be fine at all other times

[Pro60modman]

Originally Posted by MPS-Joe Nothing leaking out/nothing on the floor. I don't know what direction to go with this. Attached another pic of the AP at 70mph motorway cruise control on, trims and AFR bang on. Then a video of me pulling up to my drive and putting it into neutral where you can see the STFT creep down to -25.12, along with the AFR. Why on earth would it be pulling 25% fuel at idle, but be fine at all other times

You are missing what I'm saying. The injector could be leaking into the cylinder when it's supposed to be closed. This will cause rich idle. Pull your spark plugs and see if one is darker than the others. That's usually a good indicator or use a borescope with the key on and see if fuel sprays or leaks into the cylinder when you turn the key to the on position.

[nebolskeetskeet]

I am dealing with a very similar issue, and am in the process of trying to hound this down.

Do you have some back story? Was it fine and just started doing this? Did you change any of your parts? What tune are you running?

Like Thor Hammer said, if you have a leak at idle between the turbo outlet and the throttle body, you could be leaking out metered air. Have you done a boost leak test?

[MPS-Joe]

Originally Posted by nebolskeetskeet I am dealing with a very similar issue, and am in the process of trying to hound this down. Do you have some back story? Was it fine and just started doing this? Did you change any of your parts? What tune are you running? Like Thor Hammer said, if you have a leak at idle between the turbo outlet and the throttle body, you could be leaking out metered air. Have you done a boost leak test?

Basically I changed my ABS pump, so had my TIP, intake and battery out, trims and AFRs were fine before. Thought maybe I hadn't connected something properly, so since I have taken it all back out and put it back again, double checking clamps and pipes etc and it's still the same. Not done a boost leak test, but like I said it was fine before and I've double and triple checked what I actually touched and can't find anything.

[mituc]

Originally Posted by MPS-Joe so since I have taken it all back out and put it back again, double checking clamps and pipes etc and it's still the same.

Where is your EBCS located?

[MPS-Joe]

Originally Posted by mituc Where is your EBCS located?

3 port is installed on the front of the battery box, I have checked WG, boost and vent line, all fine.

[Solarsurge]

You said your oil level hasn't risen. Has it fallen? It's possible you have crank case pressure spitting oil into your combustion chambers at idle, causing the O2 sensor to read rich. Take off your oil cap while idling and feel for air rushing out.

[mituc]

Originally Posted by Solarsurge It's possible you have crank case pressure spitting oil into your combustion chambers at idle, causing the O2 sensor to read rich.

If this would happen then the compression was so bad that the engine would not even idle properly, not to say drive properly.
Also, the oil needs to be vapours to burn and cause a rich condition, t would ave to be a very bad (or badly worn) oil.

[Solarsurge]

Originally Posted by mituc If this would happen then the compression was so bad that the engine would not even idle properly, not to say drive properly. Also, the oil needs to be vapours to burn and cause a rich condition, t would ave to be a very bad (or badly worn) oil.

I would argue he's not idling properly, but a lot depends on how bad the problem is. I had a clogged crank case breather hose connected to my OCC and had similar idle conditions, only I was also smoking and the oil was pushing past my rings AND my turbo seals. It subsided when I drove and came right back at idle. It drove me nuts. I was told by 3 mechanics I blew a head gasket. Pulled that hose, blew through it, must have dumped a half a quart of shit out the drain valve of the OCC on the other end. Immediately, AFRs went back to normal, smoking stopped, idle was perfect. Compression also tested fine. At this point nothing surprises me. Just figured I'd throw it out there since it seems like he already covered his bases with normal troubleshooting. Never hurts to check.

[MPS-Joe]

Originally Posted by Solarsurge You said your oil level hasn't risen. Has it fallen? It's possible you have crank case pressure spitting oil into your combustion chambers at idle, causing the O2 sensor to read rich. Take off your oil cap while idling and feel for air rushing out.

Oil is fine, always keep on top of oil levels and the car hardly uses any. Is the crankcase breather pipe the one that comes off the PCV under intake mani?

[5doorsoffury]

Post a wot log. If you have a post turbo pre tb leak then you should be lean at wot and rich at idle. A bad bpv could cause hesitation and negitive negative trims.
Do you have a meth kit? And exhaust leaks?

[Thor Hammer]

Well, he still has not confirmed he has done a boost leak test. You can assume its fine before fine now, but that doesn't mean anything. Do a test and rule it out or you're just chasing your tail. Eliminate one possible cause at a time or it gets overwhelming and you go nowhere.

[MPS-Joe]

Originally Posted by Thor Hammer Well, he still has not confirmed he has done a boost leak test. You can assume its fine before fine now, but that doesn't mean anything. Do a test and rule it out or you're just chasing your tail. Eliminate one possible cause at a time or it gets overwhelming and you go nowhere.

Yeh I've not had chance to do a boost leak check yet, been busy with work. I will try and post a WOT log up though.

[MPS-Joe]

Originally Posted by 5doorsoffury Post a wot log. If you have a post turbo pre tb leak then you should be lean at wot and rich at idle. A bad bpv could cause hesitation and negitive negative trims. Do you have a meth kit? And exhaust leaks?

Here is a log from my drive to the gym from cold start, a some WOT in 3rd and 4th. Struggle for roads long enough/without speed cameras around me to get going properly.

[mituc]

So you went WOT less than 4 minutes after starting the car cold? Ok...

Under WOT apart from some oscillations everything looks decent. So does normal/part throttle driving.

Can you publish your MAF cal and say again what intake you have?

[MPS-Joe]

Originally Posted by mituc So you went WOT less than 4 minutes after starting the car cold? Ok... Under WOT apart from some oscillations everything looks decent. So does normal/part throttle driving. Can you publish your MAF cal and say again what intake you have?

Its like 30+ degrees here in the UK at the minute, temps were fine when I went WOT.

What do you mean publish my MAF cal? I have AEM intake and TIP

[Solarsurge]

Originally Posted by MPS-Joe Its like 30+ degrees here in the UK at the minute, temps were fine when I went WOT. What do you mean publish my MAF cal? I have AEM intake and TIP

Your mass airflow sensor is calibrated for the volume of air the stock intake takes in. If you change your intake and don’t re-calibrate your MAF table (tune), your MAF voltage is going to be off so your car thinks you’re taking in different air amounts than you actually are, which is going to throw off your fuel delivery.


Sent from my iPhone using Tapatalk

[MPS-Joe]

Originally Posted by Solarsurge Your mass airflow sensor is calibrated for the volume of air the stock intake takes in. If you change your intake and don’t re-calibrate your MAF table (tune), your MAF voltage is going to be off so your car thinks you’re taking in different air amounts than you actually are, which is going to throw off your fuel delivery. Sent from my iPhone using Tapatalk

Ah right ok, I've not changed anything since owning it and it's been tuned for the mods it has. Never had a problem with trims until now.