R0b

Hi guys

For some reason starting in the last week, the car runs rich when it just switches over to open loop.

I thought it would be my 02 sensor but then i had a think, the ecu would only use the 02 sensor in closed loop. In closed loop, everything is fine. 14 - 14.7 with load under 80.

As soon as the ecu clicks over to open loop however, i get afrs of 9-10 during spool and as rich as 8 from 4500rpm upwards.

Checked the fuel map and yes its all normal - have been tuned and previously running 12.8-12.5 afr for spool and 11.5 up the top.

Car hasnt had anything changed or altered recently.

Evo viii

Any clues or pointers?

Thanks

joseph143

iTrader: (8)

Fuel pressure reg might be bad. If there's nothing to tell the pump to slow down it'll run full tilt and f up the afr.

R0b

thanks for your reply.

If it was the fpr (im stock but have a walbro), wouldnt that mean that i should be running rich even in closed loop like cruising?

R0b

today i pressure tested the system - no leaks anywhere!

i really dont know what else it could be.

any guesses out there?

W2J

iTrader: (12)

check to see if you have any unmetered air slipping pass before the maf.

bigben

iTrader: (4)

^ I think you mean "after" the MAF sensor

R0b

taken the whole intake pipe etc apart. put a bright light through it and had a good look for splits and cracks - all clear and all good.

its getting too hard now =(

milford

iTrader: (18)

im guessing you did a boost leak test?

R0b

yes did it today - no leaks

i think i had a bad batch of fuel a week ago, and now its stuck in low octane fuel map mode. except timing is normal - using high octane timing maps....hmm

nonschlont

iTrader: (3)

did u check the inj. seals? Had the same symptoms, and I started feeling around the FPR and the inj. and noticed one of the seals were leaking... (air)

maxima92se

My 2cents is the fpr.. Seems like the car should run rich the whole time but the for assuming it behaves like a maxima, then it opens or regulates according to boost. Reading. Boost might kick it open and dump fuel in. Not 100% sure read the fuel pressure.. Go from there.

rstchris

iTrader: (10)

What do the fuel trims look like? Are they pegged high?

grayw

Are you getting misfires on spool with AFR's that rich? I would check the WB sensor and not just reley that's what it's reading is correct.

R0b

thanks for replies guys.

will do another pressure test later on and check the injector seals

taken a log of a short drive. mixture of city and highway
fuel trim low 4.6875 on normal driving then 6.8359 when in boost
fuel trim mid 1.5625 on normal driving and when in boost
fuel trim high -1.1718 on normal driving and when in boost

comparing the 02 sensor readings to the wideband readings is weird. i cant seem to get any correlation between the two so maybe it is just my wideband sensor?

0.91744 on the 02 shows afr of a range between 11 through to 15 on the wideband
0.8784 on the 02 shows afr of 12-13 afr ranges.

Im not getting misfires during spool. I was getting some random tip in knock, ive pulled 1 deg of timing and now theres no knock at all but afrs still remain rich starting from load 80 onwards. ive reflashed the stock rom back on, afr have gone from 9's into the 10s on spool but thats only because the stock rom has lean spool enabled and the map is slightly leaner than my tuned one.

I will have to do another log and compare the 02 with the wb

thanks again for some pointers

grayw

Stole this quote from someone else 'Remove your wideband sensor then turn it on and get it all warmed up, calibrated, etc. Then spray a rag with brake cleaner, and cover the sensor in it. A good working sensor will just go off the scale rich and hold that reading until the rag is removed. Knackared sensor will go full rich, then full lean, even though the rag soaked in brake cleaner is still applied.' There is also a video kicking around showing how to test it.

As said with AFR's that rich you would 99% likely to be getting misfires on spool and WOT.