Premix with an OMP
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Joined: May 2019
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From: San Diego
Premix with an OMP
I know this has probably already been asked, but honestly I'm not great at navigating forums and need my ten posts lol. So back to the question. Is it right to premix if your omp is still working? How do you know if it is? What are suggested ratios to be safe if you don't know if you have an OMP or not.
-92 FD
-92 FD
* First, download a copy of the Factory Service Manual from the 3rd Gen. FAQ at the top of this section...and find out what the OMP/MOP looks like and where it's located. Moving out of the new member section you will be expected to make an effort yourself to learn the basics, and such things as component location.
*If you have a stock ECU, then you have an OMP because without one the car would be in what is called "limp mode". In Limp Mode timing will not advance and fuel is cut the instant vacuum isn't sensed by the sensor in the upper intake manifold. The car will start and idle normally, but have VERY little power...hence "limp mode" so you can "limp home". There are three different codes related to the OMP. If any of them are generated it will put the car into limp mode. You WILL have to search on how to pull codes on a JDM model, as it's different than our North American LHD cars ( ain't all that JDM'ness great?)
*The only other potential issue that could arise is a leaking OMP line, but that would be apparent by the oil pooling on top of the engine.
*To answer your question, yes, it's acceptable to pre-mix with a working OMP but at a reduced rate. WITHOUT an OMP you should mix about 1 oz. per gallon of fuel. WITH an OMP...about half that, or .5 oz. per gallon. You may see a little more fouling of plugs and emissions testing would definitely be affected negatively. There are some other risks, like potentially fouling your stock cat and carbon build-up. You can search and read more at your convenience.
*If you have a stock ECU, then you have an OMP because without one the car would be in what is called "limp mode". In Limp Mode timing will not advance and fuel is cut the instant vacuum isn't sensed by the sensor in the upper intake manifold. The car will start and idle normally, but have VERY little power...hence "limp mode" so you can "limp home". There are three different codes related to the OMP. If any of them are generated it will put the car into limp mode. You WILL have to search on how to pull codes on a JDM model, as it's different than our North American LHD cars ( ain't all that JDM'ness great?)
*The only other potential issue that could arise is a leaking OMP line, but that would be apparent by the oil pooling on top of the engine.
*To answer your question, yes, it's acceptable to pre-mix with a working OMP but at a reduced rate. WITHOUT an OMP you should mix about 1 oz. per gallon of fuel. WITH an OMP...about half that, or .5 oz. per gallon. You may see a little more fouling of plugs and emissions testing would definitely be affected negatively. There are some other risks, like potentially fouling your stock cat and carbon build-up. You can search and read more at your convenience.
Junior Member
Joined: Mar 2017
Posts: 6
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From: Brentwood, TN
* First, download a copy of the Factory Service Manual from the 3rd Gen. FAQ at the top of this section...and find out what the OMP/MOP looks like and where it's located. Moving out of the new member section you will be expected to make an effort yourself to learn the basics, and such things as component location.
*If you have a stock ECU, then you have an OMP because without one the car would be in what is called "limp mode". In Limp Mode timing will not advance and fuel is cut the instant vacuum isn't sensed by the sensor in the upper intake manifold. The car will start and idle normally, but have VERY little power...hence "limp mode" so you can "limp home". There are three different codes related to the OMP. If any of them are generated it will put the car into limp mode. You WILL have to search on how to pull codes on a JDM model, as it's different than our North American LHD cars ( ain't all that JDM'ness great?)
*The only other potential issue that could arise is a leaking OMP line, but that would be apparent by the oil pooling on top of the engine.
*To answer your question, yes, it's acceptable to pre-mix with a working OMP but at a reduced rate. WITHOUT an OMP you should mix about 1 oz. per gallon of fuel. WITH an OMP...about half that, or .5 oz. per gallon. You may see a little more fouling of plugs and emissions testing would definitely be affected negatively. There are some other risks, like potentially fouling your stock cat and carbon build-up. You can search and read more at your convenience.
*If you have a stock ECU, then you have an OMP because without one the car would be in what is called "limp mode". In Limp Mode timing will not advance and fuel is cut the instant vacuum isn't sensed by the sensor in the upper intake manifold. The car will start and idle normally, but have VERY little power...hence "limp mode" so you can "limp home". There are three different codes related to the OMP. If any of them are generated it will put the car into limp mode. You WILL have to search on how to pull codes on a JDM model, as it's different than our North American LHD cars ( ain't all that JDM'ness great?)
*The only other potential issue that could arise is a leaking OMP line, but that would be apparent by the oil pooling on top of the engine.
*To answer your question, yes, it's acceptable to pre-mix with a working OMP but at a reduced rate. WITHOUT an OMP you should mix about 1 oz. per gallon of fuel. WITH an OMP...about half that, or .5 oz. per gallon. You may see a little more fouling of plugs and emissions testing would definitely be affected negatively. There are some other risks, like potentially fouling your stock cat and carbon build-up. You can search and read more at your convenience.
^ You might consider checking out the the auxiliary injection section. If you just have mild mods a simple (and inexpensive) Water Injection system can help with any potential carbon issue. You also get cooling and knock suppression with it. The key is proper nozzle sizing, which is covered in that section’s sticky’s. If curious, you can search for threads under my screen name to see what I did.
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