Comments by "Mike Chiodetti" (@mikechiodetti4482) on "Toyota Fuel Trims and live data diagnosis tips!" video.

  1. Fuel trims can throw you. For example. Watch when your LFT reads 12.5 and your SFT reads -10.5. This can confuse people, but actually, your TOTAL fuel trim is +2.0 or 2.0. The short trim is removing fuel, but the LFT is taking its time to reduce. I've seen this after a repair. The fix was to reset the fuel trims and watch. The engine has about 40K on it and the SFT reads from -7% to +7%, and it stays that way. There's other scenario's, and only by learning how SFT and LFT work with the AFR sensors is it understood. I saw one Ford V10 van that both banks LFT and SFT reading at +25% each for a combined TOTAL Fuel Trim of 50% each bank. This was at idle. As the throttle was opened slowly to 2000 RPM's, LFT's and SFT's settled down with LFT's approximately between 6 to 8% and SFT's approximately between -7 to +7%. At idle, the van shook so bad, I thought the ladders would fall from their roof racks. The cause was a tear in the PCV hose on the bottom of the hose near the port on the throttle body. Ford had an upgrade for this with a thicker hose material. With the the new hose installed, fuel trims came down, no more shaking and all was well in Ford land. The tear wasn't big, only about 1 inch long, but the engine heat and vacuum caused the tear to turn inward toward the inside of the hose. It was that thin! A tech learning about fuel trims needs to work with vehicles that are running good to get a baseline understanding of that system. Disconnect then reconnect a small vacuum hose and watch the readings. I had to learn fuel trims AND the Ford WDS diagnostic system we had before we got the IDS which I understand is still in use. Thankyou for this video.
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