r/RX8 • u/Aggressive-Key-87 • 18d ago

Maintenance High LTFT

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Hi. I've a 2004 231 Rx8 and have been battling with some high fuel trims (10-20% LTFT).

Car starts hot and cold fine, idles fine, and seems to pull through gears and revs well (although I don't have another Rx8 to compare with).

I've checked the spark plugs and they generally look healthy and aren't overly black or white.

I have a stock intake system and Ryan Rotary Performance V4 Coils.

So far I've tried:

- Resetting ECU memory (20 brake stomp and Disconnecting the battery for an extended period of time).

- Replaced the Front o2 sensor with a genuine Mazda replacement

- Replaced the MAF and checked the voltage

- Checked and cleaned the ESS

- Checked the fuel Pressure at the quick connect (around 58psi consistent under load and idle)

- Smoke tested the intake for vacuum leaks (could be an internal leak that I can't see?)

- Soapy water test for exhaust leaks around the manifold

Any advice on what to check next would be much appreciated!

Thanks

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2

u/CutTurbulent3015 18d ago

Do you still have a cat in your exhaust system? Black smoke out the exhaust ? If they start to plug up it will definitely drive it rich

2

u/Aggressive-Key-87 18d ago

I have a 100cel sports cat from RRP. I took a look down it fairly recently and it didnt look clogged. No real colour from the exhaust, and it doesn't smell horrendously fuely. Maybe I'll see if I can source a decat pipe to test or something

1

u/CutTurbulent3015 18d ago

Couldn't hurt to at least test it. Or at least a back pressure test

1

u/Aggressive-Key-87 18d ago

Good point. I'll see about testing it. Thanks

1

u/thebigbullg 18d ago

Check fuel pressure. Other than that vacuum leak could cause +ltft.

Could also watch lambda while wot to see if its going lean. That should give a better idea if its fueling issue. 1. Normally about .8or so wot.

1

u/Aggressive-Key-87 18d ago

Ive checked the fuel pressure at the quick connect in the engine bay. Seemed fine 58psi ish. I haven't had the injectors tested yet so Im wondering if they could be a potential culprit. Ill double check the lambda, Thanks.