Quote:
Originally Posted by JMat
This is a relatively new issue and only happens after 100+ mile drives at highway speeds. This is a '98 3.4l auto 4x4.
After driving for for a long period at highway speeds and the car has been running great I hit the offramp and have to stop for a red light and my long term fuel trim drops to +1.56%(my usual long term fuel trim at idle is +3.12%) the engine is almost stalling and the Short Term Fuel Trim is jumping around between +18% to +20%. The light goes green, I step on the gas and the car is running fine again, no lack of power and not rough(fuel trims quickly return to "normal"). I drive it the mile home and pull in to garage, leave it in gear and the fuel trim drops back down to +1.56% and the STFT starts bouncing around -17 to -19%.(180degree flip on STFT) and after checking the exhaust it's definitely running rich.
Plugs, wires(NGK) and O2 sensors(OEM) are less than a year old and under 20k miles. MAF has been cleaned within 5k.
Any ideas on where to start? I'm at a loss.
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How about when the fuel filter was last changed and what the fuel pressure is at the fuel rail?
Along with the air filter?
How many miles on the rig and are your O2 sensors resistance in spec?
Spark plug wires and coils within reistance spec?
I was just thinking at starting at the beginning and working forward. :-)
Once the engine is warm your engine will run off the O2 sensors instead of the static mappings in the ECM.
Your O2 sensors are floating around. So they seem to be working I just wondering if anything is close to the resistance limits, thus causing this very odd dip from highway driving.
Also is your 98 a Federal or CA emissions system?
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7 3rd gens listed in the build thread (2 are parts mobiles)
Build Thread:
https://www.toyota-4runner.org/3rd-g...os-builds.html
Brillo's Bucket Fluid Ex changer:
https://www.toyota-4runner.org/3rd-g...ml#post3358086
Sparks Plugs Wire and Coil Information:
https://www.toyota-4runner.org/3rd-g...on-5vz-fe.html
