Engine Check Light - Adjust the Valves???

[Gulfstream Greg]

So here is my story of the check engine light illuminating on our 91 V6 with 85K on the speedo. We planned a trip to the North Coast into Oregon and back. So I felt it was relevant to install some new spark plugs, cap, rotor etc since the rig was new to us and the history unknown. Engine seemed to run just fine, how would I know a difference, did not have the rig that long and only a few short trips and never had any experience with the V6 motorhome. So off we went. Completed the trip with flying colors except for the AC belt (another story). The next week after getting back I drove it to work so to fill the propane tank. That's when the check engine light came on. I checked the codes as per the Chilton's instructions and got two different ones. 1- running rich and 2- running lean. My guess is an O2 sensor bit the dust. I had just replaced the one before the catalytic converter and knew how much they cost. I reset the light 4 times total. So I opted to have a local mechanic look at it. His opinion (Toyota service center mechanic for many many years) was that the valves needed adjustment. A task done via shims on the V6 and also that I had the wrong plugs installed even though the plug manufacturer crossed them over to work just fine. So a valve adjustment and some new shiny NGK's we were off on another trip to the Sierra Foothills. The light has stayed off and the amazing thing is there is a very noticeable power increase on hills. So my hat is off to the wisdom of experience. The guy had seen the same problem many many times and new what to do. The Toyota God of motorhomes was looking out after us on that day!

[RalphE]

So here is my story of the check engine light illuminating on our 91 V6 with 85K on the speedo. We planned a trip to the North Coast into Oregon and back. So I felt it was relevant to install some new spark plugs, cap, rotor etc since the rig was new to us and the history unknown. Engine seemed to run just fine, how would I know a difference, did not have the rig that long and only a few short trips and never had any experience with the V6 motorhome. So off we went. Completed the trip with flying colors except for the AC belt (another story). The next week after getting back I drove it to work so to fill the propane tank. That's when the check engine light came on. I checked the codes as per the Chilton's instructions and got two different ones. 1- running rich and 2- running lean. My guess is an O2 sensor bit the dust. I had just replaced the one before the catalytic converter and knew how much they cost. I reset the light 4 times total. So I opted to have a local mechanic look at it. His opinion (Toyota service center mechanic for many many years) was that the valves needed adjustment. A task done via shims on the V6 and also that I had the wrong plugs installed even though the plug manufacturer crossed them over to work just fine. So a valve adjustment and some new shiny NGK's we were off on another trip to the Sierra Foothills. The light has stayed off and the amazing thing is there is a very noticeable power increase on hills. So my hat is off to the wisdom of experience. The guy had seen the same problem many many times and new what to do. The Toyota God of motorhomes was looking out after us on that day!

[RalphE]

I wish you the best of luck on curing the check engine light problems. In the past I have done all the things that you did. each time the truck ran great for 20-30 K. Than the light came on again. A valve grind at $1600 a valve adjustment $1100 belts plugs timming after Oxygen sencer $700. And still having the problem. Ralph

[Gulfstream Greg]

I wish you the best of luck on curing the check engine light problems. In the past I have done all the things that you did. each time the truck ran great for 20-30 K. Than the light came on again. A valve grind at $1600 a valve adjustment $1100 belts plugs timming after Oxygen sencer $700. And still having the problem. Ralph

Ralph - I have read your posts on this subject and I hope I do not end up with the same results. Have you put in new camshafts? Just a thought. They may have worn prematurely. Anyhow we only have about 1000 miles since the valve adjustment. We will be lucky to put 3000 on a year so it might take awhile to test the theory.