GS300 Running Rich

[itspalm]

Car has been running rich for around the past month, I've replaced the 02 sensors and made sure they're on snug, new MAF sensor, new TPS, New Injectors, New Fuel Pump, New spark plugs, new coil packs but it's still running rich. I've tried unplugging the battery overnight to try and reset the ecu but nothing is working. Does anyone have any suggestions on anything I should look at or attempt in order to fix this issue? My long term fuel% trim is at -40% for both bank 1 and bank 2.

[Dean2]

Check for an intake manifold leak. If you have a leak, additional air is being pulled into the engine and the ECU will add fuel to balance it out. Causes really poor gas mileage and what appears to be a run rich scenario.

[itspalm]

7 hours ago, Dean2 said:

Check for an intake manifold leak. If you have a leak, additional air is being pulled into the engine and the ECU will add fuel to balance it out. Causes really poor gas mileage and what appears to be a run rich scenario.

How would you recommend i check for this?

[Dean2]

With car warm and idling spray flammable throttle body cleaner around the intake manifold gasket. If it is sucking air you should be able to hear a difference in the idle rpm.  Also, if you have a live OBD reader you should be able to read the vacum level. Also, you can use an old style vacum gauge, it should read 18 or more, if you have a vacum leak it will read a lot lower.

[itspalm]

I recently replaced the intake manifold gasket so I really doubt its a leak, I will check but incase it isn't do you have any other suggestions? Also is this something that i could potentially get tuned and fixed that way? 

[Dean2]

If you just replaced the intake gasket recently then I would for sure be checking for a leak there. Once you have checked let me know the results. Are there any error codes stored. Have you done an obd code read?

[itspalm]

Its throwing up 2 codes, bank 1 and bank 2 running too rich

[Dean2]

Well, outside bad O2 sensors, plugs, coils, plugged pcv and you already changed those I am left with you are getting extra air from somewhere, or your ecu needs to be reset and the ecu being off, unless you did something to change its programing, doesn't seem real likely. Does the car idle at normal rpm, and does it drive normally, just sucking a lot of gas?

[itspalm]

It runs good, idle is slightly high at first but once it warms up its normal, and yes its sucking quite a bit of gas.

[Dean2]

So, did you get it sorted? What was the cause of it running so rich?

[Anner]

It seems I am having a similar issue, I just ordered some new NGK coils, wires and spark plugs along with OEM Denso fuel injectors, we have the same year make and model, mines idles high when warming up but after the warm up it is normal, however the misfires feel more like a stutter than anything, they don't feel that bad however it is noticeable and bothers me alot, I have CEL for P0300, P0301, P0303 and P0305, so misfires in cylinders 1,3 and 5. I hope everything I order will help me fix this issue if not then we will see, but I digress, if there are any people here who can give me any advice on why my car is still suttering that would be great thank you!