Got a doozy on my hands.
A few weeks ago, my parents' 1999 LC (with 320k miles) developed a cylinder #3 misfire on startup that would go away after about 30 seconds. Seemed like an injector leaking into the cylinder while sitting, so I had them run some fuel system cleaner and drive it like a maniac and that cleared it up for a few days.
So I swapped in a full set of brand new Denso injectors and reset the ECU.
It ran absolutely perfect for one drive cycle. But now the fuel trims are -20% at idle and get worse with RPM. All four O2 sensors are pegged at 0.9v at idle and only start oscillating once RPMs increase.
The misfire is spreading across the entire driver's side cylinder bank. Not just cylinder 3 anymore, but 1 and 7 will misfire on startup now too.
And the longer it sits between starts, the worse misfiring is. Swapping sparkplugs and coils around didn't change a thing.
Smells absolutely terrible while running--super rich and gunpowder-y.
Swapped in a new MAF cuz that's cheap and easy and if it fixes it, yay, if not, we know something else is up. Not like the old one didn't live a long and useful life.
But that didn't help at all. Something else is definitely up, and I'm at a loss.
I can't imagine it being the injectors, since 1) the misfire is still there+getting worse and 2) it ran so beautifully for that first drive after resetting the ECU I couldn't feel the engine running.
I took the ECU out and opened it and can't see anything obviously wrong. None of the caps are bulging or leaking, no visibly-bad solder joints...
The main ECU ground on the back of the passenger side of the engine is nice and secure.
What next?? HELP!
(As a PS, I had a similar-but-opposite problem on my old Lexus GS400 a while back. Regular voltage at all four O2 sensors at idle, but would drop to zero when giving it any throttle. Turned out to be a grody fuse and replacing that fixed it right up. This is the opposite. Like too much voltage until the engine is under load.)
A few weeks ago, my parents' 1999 LC (with 320k miles) developed a cylinder #3 misfire on startup that would go away after about 30 seconds. Seemed like an injector leaking into the cylinder while sitting, so I had them run some fuel system cleaner and drive it like a maniac and that cleared it up for a few days.
So I swapped in a full set of brand new Denso injectors and reset the ECU.
It ran absolutely perfect for one drive cycle. But now the fuel trims are -20% at idle and get worse with RPM. All four O2 sensors are pegged at 0.9v at idle and only start oscillating once RPMs increase.
The misfire is spreading across the entire driver's side cylinder bank. Not just cylinder 3 anymore, but 1 and 7 will misfire on startup now too.
And the longer it sits between starts, the worse misfiring is. Swapping sparkplugs and coils around didn't change a thing.
Smells absolutely terrible while running--super rich and gunpowder-y.
Swapped in a new MAF cuz that's cheap and easy and if it fixes it, yay, if not, we know something else is up. Not like the old one didn't live a long and useful life.
But that didn't help at all. Something else is definitely up, and I'm at a loss.
I can't imagine it being the injectors, since 1) the misfire is still there+getting worse and 2) it ran so beautifully for that first drive after resetting the ECU I couldn't feel the engine running.
I took the ECU out and opened it and can't see anything obviously wrong. None of the caps are bulging or leaking, no visibly-bad solder joints...
The main ECU ground on the back of the passenger side of the engine is nice and secure.
What next?? HELP!
(As a PS, I had a similar-but-opposite problem on my old Lexus GS400 a while back. Regular voltage at all four O2 sensors at idle, but would drop to zero when giving it any throttle. Turned out to be a grody fuse and replacing that fixed it right up. This is the opposite. Like too much voltage until the engine is under load.)