Quote:
Originally Posted by Shadow6
So I got a chance to start going through the FSM helpfully linked above, and I’m able to determine that I’ve got a “lean imbalance” detected using the crank speed sensor. This matches up with my freeze frame LFTs and SFTs, which are both slightly positive.
The first test is using the Toyota diagnostic equipment to change injection volumes and look at misfire counts to determine which cylinders are causing the issue. I don’t have the Toyota diagnostic equipment of course, so instead I just did a long test drive while keeping an eye on my misfire count PID.
Cylinders 2 and 3 are normal, 0 misfires once warm. Cylinder 1 gives me up 3-4 at idle once warm. Cylinder 4 gives me up to 13 at idle once warm. All four stay at 0 at cruising RPMs. I do not get a misfire DTC.
I checked the intake manifold with a smoke machine, no leaks there now that I’ve replaced the throttle body. I don’t hear an exhaust leak.
So at this point the next steps involve the spark plugs and then the injectors (both port and direct). I’m thinking with 80k+ miles maybe I just throw a new set of plugs at it anyway and see if that changes anything, since they’re probably about due. Maybe swap coils around after if I’m setting the same misfires?
Any other thoughts?
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Is it possible that an inaudible exhaust leak could throw off your afr? Slight crack in the header? I saw a post where a leak at the header/overpipe gasket caused an afr problem. A small leak would be hard to hear over the noise of a Russian tractor engine. It's relatively easy to check and replace gaskets.