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The mkiv Supra Owners Club

Running rich or lean


ballsdeep

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I can't work out why my afr's are showing rich at idle and cruising but don't have any running issues? Everything seems to feel just how it did after mapping, I can't find any vac leaks and Iv swapped out the o2 sensor for my spare until my new one arrives but the readings from ox1 pin still show 0.3v

 

cold - 10.6

Warm - 11s 12s

Cruising - 13s

Short boost runs - 11s

 

There was 2 changes I made which I think was before I realised the afr's was off

 

Charcoal canister was put back in and spark plug gap opened to 0.28 then ecu reset but Iv since put things back exactly how I had it before just for peace of mind.

 

Any other checks I can do before I get it booked in? Could it be a fuel pressure issue or map sensor? Iv forgot how to check the map sensor I get 5v from pin1 what should I get from the other 2

 

Thanks

Edited by ballsdeep (see edit history)
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Fraid not I regret not installing one now, is it something I could install without having the map tweaked?

 

I'm pretty sure it used to be in the 14s at cruising

 

13 - 14 seems right for cruising.

 

AFR reading

 

start up 10 - 12

warm idle 13 -14

cruise 13 - 14

Boost 11 - 12

 

closed throttle 17+

 

 

I don't see why not. Find out on what psi should your injectors should be running, set your fuel regulator to that psi. Then check the AFR to see what its reading.

 

You are better off running rich than lean.

Edited by Dim Sum (see edit history)
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I would first look at the ECU coolant temp sensor, if this has failed the ECU will run things rich by default resulting in a rich mixture, and this will be more apparent during closed loop IE idle and cruising, however if the lambda voltage is not fluctuating that could also be the problem and have the same result.

 

Its unlikely to be the FPR as the rich mixture would likely carry on through the load range.

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The coolant temp sensor is fairly new but I would like to test it again to rule it out, could you remind me of the procedure pls Ricky.

 

Lambda just gives a solid 0.3v but it's exactly the same with my spare even after the lemon juice trick, my new one should arrive soon so I can try that one.

 

Thanks

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You say it was fine after mapping?

 

What ECU is fitted, how did you reset it?

 

What AFR sensor is it using, a static voltage doesnt sound correct as it should be constantly changing is it a wideband sensor or stock narrowband?

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I don't think it needs to be calibrated? it's the aem afr gauge I'm not convinced it's a faulty reading just yet as there is strong fuel smell from the exhaust at times!

 

I forgot how difficult it is to get at that bloody water temp sensor but I managed to take a reading from it this morning so after Iv drove to work il take another, same goes for the ait sensor.

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Running e-manage ultimate and I only pulled the efi fuse to reset the stock ecu, I have the aem afr gauge but its not hooked up to the emu and then one oem o2 lambda sensor.

 

Any reason you reset the ECU?

 

As the EMU is not using any feedback the corrections it applies will be static, from memory the stock ECU is not, it learns over time trimming fuel and ignition, its a very clever box of tricks and the reason so many engines havent gone pop :D

 

Its possible you now have the EMU applying the same trims as before to essentially different base maps.

 

I cant remember, does the EMU support wideband feedback? If it does I would be looking to hook that up since you have one installed ;)

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EMU can run a wide-band or narrow-band feedback, but not control wide-band, however its kind of pointless unless your using the self learn/target AFR setting, which doesn't work that well anyway.

I was always under the impression that the std ECU, like most can only learn short term fuel trim of idle and cruse, along with knock map for fuel grade, never had any problems erasing these when using EMU, besides its pretty much un necessary to change much map wise unless you are single.

 

Sounds like the std lambda is goosed to me.

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I'm guessing the water temp and intake temp sensors or working OK as I got 2 different readings from cold and warm.

 

All I can do at this point is wait a few more days until my new lambda sensor arrives, in the mean time is it worth unplugging it for now?

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Disconnecting the lambda sensor wont change anything, the ECU will still run things a bit rich by default, as it still thinks the sensor is dead,

If IAT sensor is dead it wont change anything other than loosing temp related fuel trim, as its not a large adjustment, unlike the ECU coolant temp and lambda.

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Wish I new mate? :( I need to learn how to datalog for any future issues but for now I'm stuck until I can get it booked in somewhere!

 

Just tried my spare Ecu and new plugs just because I don't know what else to check but it's still no good, is there any testing procedures for the map sensor?

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Sorry I miss read your " need to learn" bit, no as I said resetting the std ECU just makes it erase the short term fuel, and timing trim, and relearn idle, so it wont effect the EMU, however I guess it could have had a hiccup and developed a problem.

its an odd one, but I still suspect that despite replacing both the ECU coolant temp sensor, and lambda sensor there may be a problem with the wiring perhaps.

Edited by Tricky-Ricky (see edit history)
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Certainly is strange if it wasn't for the smell of petrol low afr numbers I'd be clueless, I would have though I'd be suffering from a misfire but it runs great and idles perfect.

 

I know it's hard to read plugs but would you say these are showing a lean condition not rich??

 

image

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