Hi, I'm new to the site and have a problem. My 99 full size Montero's check engine light came on. After having the OBDII codes read my mechanic said that both catalytic converters need replacement. This replacement would be several thousand dollars and I am very hesitant to get the work done on a vehicle with close to 140,000 miles. To make matters worse I live in Maryland and have an emissions test upcoming. Does anyone have any thoughts on what I should do? Thanks.

If it was me I'd possibly look at removing the Cats and running E85 ethanol. It would take some work to get set-up correctly for the fuel (injectors, timing, fuel filter, ect) but I have heard from several owners in the States that have had good sucess with the conversion. It not only reduces your emissions but the engine runs better and has more performance, etc. It may also be cheaper running costs depending on your local prices.

Unfortunatly, I don't know of anyone using in a Mitsi Montero but I'm sure your mechanic can advise on if its possible. Keep us posted.

Jim

Wut were the codes? That the threshold on the downstream sensors were below normal? These usually do noit go , bad the catalytic converters , I have seen both downstream (oxygen sensors after catalytic converter) go bad , also on these models there can be various reasons that the these sensors can show a catalyst fault . Can yu post wut the codes are so we can more accuratelly help. In lots of cases i have seen and remedied , for instant catalyst codes , one way , and most of the time this is the case , is a catalytic convertor over age the inner screen and shell deteriorates, basically making the flow out of the catalytic converter higher , thus transmitting more outlet heat. The HO2Sensor after the catalytic converter pics up O2 levels but most importantly heat levels. If there is a higher flow of heat , heating the sensor higher than normal ranges in certain situations a catalyst code will be set. It works the same if the catalytic convertor is plugged , by the variance in the heat pattern. On way to remedy the first situation is to reposition the HO2Sensor out of the direct heat flow, using either a threaded extension , such as a spark plug non-fouler , which is the same size and thread as the sensor , using either a short or longer one and welding it into the exhaust pipe , moving the tip of the HO2Sensor out of the higher direct heat flow , thus correcting its emmissions back to normal .Performing this method will give the HO2S a normal heat flow .

Thanks for the info. The code as it was relayed to me was a "dual catalyst failure". Your thoughts on the O2 sensor make sense, and that may be the method I use to correct this problem. The state of Maryland requires the check engine light is off at the time of testing or you automatically fail the emissions test, which is simply done with a OBDII scan. On this note, any thoughts out there how I can "beat the test". Thanks.

Disconnect the light!!!! LOl.... no that probly wont be sie but Ive seen people do it. Some times depending on the car and the code you can erase the code and it will give you a certain amount of time before it come up again, but there is no true way to "beat the test"

Actually i have said just how to beat the test and also correct the issue. Doing the method i explained would make the emission system return to a normal status. With the sensor out of direct heat range it would perorm as original . Also disconnect the light? Lots of places are alot smarter now and do look for the check engine light to go on with key on and then turn off when running. If the do not see the chec engine light come one and then go off when runnig they will suspect the bulb is burnt or has been taken out and will require it to be fixed before testing can be completed to pass inspections. Depending how high the flow is , this code usually takes 5-8 key cycles and a little driving before it will be present , Yu can also disconnect the battery for a minute and it will reset the MIL , and should be off for about a day , incase yu decide to get tested while its off.

Just a thought. I had the same codes come up and the dealership replaced my catalytic converters. Pricey!! I passed inspection and shortly after the exact same code came back.

Long story short, I ended up rebuilding my enginge and when I did I found out that both of my exhaust manifolds had huge cracks in them. I replaced those. I just wonder if this could cause that code?

Yes it can. I sorta explained that a little , when i was explaining the codes. Yu see the Heated Oxygen Sensors in these sensors , unlike the older models with non heated sensors , these new systems with heated sensors have a smaller variance than non heated sensors. So the ECU has a not as broad range it will read on , so any thing out of that range will set turn on the MIL/CEL. With cracks in the system before the heated oxygen sensors will reduce maniold and exhaust heat. The heated sensors are specified to pick up specific heat pattern and range , if teh exhaust has a leak it will not heat the sensors to the specified ranges. And set off the MIL. A catalyst code rarely is the catalytic converter itself.

i have been driving with my check engine light on for over 2 years now. i had my montero diagnosed and obd said O2 sensors but after checking, cleaning, and replacing the sensors, the check engine light returns. funny thing is it continues to pass the required emissions test. i've learned to live with this annoyance after trying all the suggested remedies i.e. resetting using obd computer, removing battery poles, etc. i have thought of removing the bulb but a mechanic said to keep it on because in case of major engine problems light would blink and this could prevent expensive repairs.

it all depends on the codes yu are having , i have successfully been able to remedy the codes ive had . Wut is the code yu have?