2004 Toyota 4Runner 4.0 Running Lean
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"an open mind let's knowledge flow in and wisdom flow out for a man who has neither never listens to those who have both".
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Everything I have read suggests a vacuum leak but I cannot find one. I have smoked this thing and have found nothing. I hosed it down with brake cleaner with absolutely no change in the short term
The brake booster is a vacuum leak source. You would have to look under the dash where the brake rod comes through the firewall. Pinch or block off the brake booster vacuum line and check trims again.
"an open mind let's knowledge flow in and wisdom flow out for a man who has neither never listens to those who have both".
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- John Clark
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- John Clark
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The other thing I've seen cause issues are the O2 sensors. The downstream sensors are often providing some means of fuel control when the upstreams are wideband O2's (air/fuel ratio sensors.) I've seen faulty downstream sensors cause high fuel trims. You want to make sure you're using only NTK or Denso O2 sensors, and preferably Denso as that's what Toyota used from the factory.
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You said the MAF is new? Is it an OE Toyota part? If not, it's VERY suspect. So many aftermarket components like that are pure junk and don't work properly even when new. Connect your scan tool and take it out and do a wide open throttle run in first gear while looking at your O2 data. The upstream O2's should go full rich during your wide open throttle run. If you're unfamiliar with how wideband O2's (air fuel ratio sensors) work then use the downstreams as they should go full rich, as well. If they do, that means fuel delivery is fine. If you don't have a vacuum leak that really only leaves the MAF. What does it show in grams per second at idle on the scan tool?
The other thing I've seen cause issues are the O2 sensors. The downstream sensors are often providing some means of fuel control when the upstreams are wideband O2's (air/fuel ratio sensors.) I've seen faulty downstream sensors cause high fuel trims. You want to make sure you're using only NTK or Denso O2 sensors, and preferably Denso as that's what Toyota used from the factory.
I am going to run this thing shortly. I will try to graph all of the data you suggested and will post it when completed. I am unfamiliar with wideband O2's and need to do some learning on those.
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You said the MAF is new? Is it an OE Toyota part? If not, it's VERY suspect. So many aftermarket components like that are pure junk and don't work properly even when new. Connect your scan tool and take it out and do a wide open throttle run in first gear while looking at your O2 data. The upstream O2's should go full rich during your wide open throttle run. If you're unfamiliar with how wideband O2's (air fuel ratio sensors) work then use the downstreams as they should go full rich, as well. If they do, that means fuel delivery is fine. If you don't have a vacuum leak that really only leaves the MAF. What does it show in grams per second at idle on the scan tool?
The other thing I've seen cause issues are the O2 sensors. The downstream sensors are often providing some means of fuel control when the upstreams are wideband O2's (air/fuel ratio sensors.) I've seen faulty downstream sensors cause high fuel trims. You want to make sure you're using only NTK or Denso O2 sensors, and preferably Denso as that's what Toyota used from the factory.
I am unable to attach documents for some reason. Here is some of the data I pulled:
Key On Engine Off
Calculated Load: 0%
MAF: 0.65 g/sec
STFT B1: 0
LTFT B: 29.64
STFT B2: 0
LTFT B2: 29.64
B1S1: 3.303V
B1S1 Equivalence Ratio: 1.001 Lam
B2S1: 3.305V
B2S1 Equivalence Ratio: 1.002 Lam
B1S2: 0.035V
B1S2 Fuel Trim: 99.06
B2S2: 0.015V
B2S2 Fuel Trim: 99.06
Low Idle
Calculated Load: 12%
MAF: 3.00 g/sec
STFT B1: 3.9
LTFT B1: 29.64
STFT B2: 7.02
LTFT B2: 29.64
B1S1: 3.319V
B1S1 Equivalence Ratio: 1.008 Lam
B2S1: 3.344V
B2S1 Equivalence Ratio: 1.008 Lam
B1S2: 0.115V
B1S2 Fuel Trim: 99.06
B2S2: 0.075V
B2S2 Fuel Trim: 99.06
Wide Open Throttle 1st Gear
Calculated Load: 78%
MAF: 164.35 g/sec
STFT B1: 0
LTFT B1: 2.34
STFT B2: 0
LTFT B2: 3.90
B1S1: 4.997V
B1S1: Equivalence Ratio: 1.117 Lam
B2S1: 4.997
B2S1: Equivalence Ratio: 1.234 Lam
B1S2: 0.015V
B1S2: Fuel Trim: 99.06
B2S2: 0.00V
B2S2 Fuel Trim: 99.06
60 MPH
RPM: 1853
Calculated Load: 22%
MAF: 17.46 g/sec
STFT B1: -2.34
LTFT B1: 22.62
STFT B2: -1.56
LTFT B2: 23.40
B1S1: 3.308V
B1S1 Equivalence Ratio: 0.994 Lam
B2S1: 3.270V
B2S1 Equivalence Ratio: 0.998 Lam
B1S2: 0.585V
B1S2 Fuel Trim: 99.06
B2S2: 0.465V
B2S2 Fuel Trim: 99.06
I realize this isn't the ideal way to show data but as I said, it won't let me upload attachments right now and I haven't figured out how to get recorded data to a graph in Auto Enginuity.
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