2010 GX460 with ~225k miles, owned 10 years and it's been solid. Historically, the dealer has done any work beyond basic maintenance and I've been happy with them, but as I've modified the vehicle over the years I'm transitioning to a local Lexus/Toyota specialist. This shop repaired a newly discovered coolant valley leak, and they asked if I wanted to replace spark plugs while they had everything off the top. They were last replaced ~120k so I said sure.
Upon receiving the vehicle I immediately noticed a significant reduction in power. It was erratic and quickly got progressively worse. I'd be driving with limp-mode level of power (which I experienced with the secondary air injection issue years prior), and I could be pretty deep on the throttle when it would return to full power and lurch forward. Scary. No check engine or any other dash light, no codes. I returned it to the shop that did the work, and they drove it and acknowledged/replicated the problem. They were puzzled by lack of codes, checked plugs and connections, didn't replace anything. They ended up disconnecting the battery and "touching the clamps together to reset the system and drain capacitors in the ECU" (their words, not mine). I'm dubious of the explanation but they didn't charge anything and it seemed fine afterwards. Maaaaybe it was still a little down on power, but I convinced myself that it was in my mind because it was much improved and generally downshifted about when I expected it to when I got on the gas.
But now after having driven it for a while, I believe it is slowly returning to a "gutless" state, and the mileage is definitely worsened. I've been lifted on 33s for a while, and I'm used to getting 13 mpg on a pure city/surface street commute, and 17 on the highway (dash indicated, not corrected). Now I'm getting 11.5-12 and 14.5-15 highway with more downshifting. And it's been a while so I'm pretty sure about it.
My instinct says plugs/coils. Any other possibilities to consider or eliminate? Any troubleshooting I can do with basic tools and multimeter? I've lost confidence in the shop I've been using so if the next step is definitively 'check the plugs and replace the coils' I'll do that myself. Otherwise if it's open ended and could be several things, I suspect I will take it to the dealer and tell them the history. I appreciate any insight you guys can offer, so I can get back to just posting pics of cool places I've driven through.
Thanks!
Upon receiving the vehicle I immediately noticed a significant reduction in power. It was erratic and quickly got progressively worse. I'd be driving with limp-mode level of power (which I experienced with the secondary air injection issue years prior), and I could be pretty deep on the throttle when it would return to full power and lurch forward. Scary. No check engine or any other dash light, no codes. I returned it to the shop that did the work, and they drove it and acknowledged/replicated the problem. They were puzzled by lack of codes, checked plugs and connections, didn't replace anything. They ended up disconnecting the battery and "touching the clamps together to reset the system and drain capacitors in the ECU" (their words, not mine). I'm dubious of the explanation but they didn't charge anything and it seemed fine afterwards. Maaaaybe it was still a little down on power, but I convinced myself that it was in my mind because it was much improved and generally downshifted about when I expected it to when I got on the gas.
But now after having driven it for a while, I believe it is slowly returning to a "gutless" state, and the mileage is definitely worsened. I've been lifted on 33s for a while, and I'm used to getting 13 mpg on a pure city/surface street commute, and 17 on the highway (dash indicated, not corrected). Now I'm getting 11.5-12 and 14.5-15 highway with more downshifting. And it's been a while so I'm pretty sure about it.
My instinct says plugs/coils. Any other possibilities to consider or eliminate? Any troubleshooting I can do with basic tools and multimeter? I've lost confidence in the shop I've been using so if the next step is definitively 'check the plugs and replace the coils' I'll do that myself. Otherwise if it's open ended and could be several things, I suspect I will take it to the dealer and tell them the history. I appreciate any insight you guys can offer, so I can get back to just posting pics of cool places I've driven through.
Thanks!