Bought a K&N air filter. cold air system. I have a 1996 850 T Wagon with 250,000 miles. Filter gives car a lot more zip. There is a bit of intake noise and a sucking sound when you back off gas.
Now the problems. On Full throttle blast car cuts out for a second on the way to hyper speed then resumes.
In stop and go traffic engine starts to miss a bit at first and it gets worse and worse till it is really missing as you accelerate. Sometimes get check engine 172-too rich or engime knock sensor codes.
I tried Premium gas. no help. It have been below zero here and maybe the intake air is too cold? Removing the air box does get rid of temp compensators.

anyone had similar problems. any Ideas?

The air intake on the old BTCC wagons was HUGH - a cone the size of the grille almost!

But, a lot of people toss out an old paper filter and put in a K&N and a cold air kit and think that they have a lot more zip.

If you really want to tell how you did, first get your car to stage I, then do a few speed runs with hearing protectors on. (Hey the speed run is illegal, so hearing protectors ((ear muff style)) are not really bad) Bring a friend to listen for trouble - THEN put your stuff on and do the speed runs again.

Getting back to my first comment - the air intake on my '96 855R is less than 8 square inches - less than 4" x 2" and it IS a cold air intake. I think that it goes pretty good!

There is more to producing power than an air intake - for instance gas speed in the entire system has to be within certain limits to produce the best power - notice how small the pipes actually are on high powered motorcycles.
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'96 855R,'64 PV544 driver, '67 P1800 basket case, '95 855, '95 854, the first three are mine, heh, heh, 485,000 miles put on 9 bricks

Personally, I would not use K & N Filters in your vehicle. They are known for allowing great amounts of air in, but at the same time that volume of air is also allowing more dirt to flow into your vehicles internals. This will cause excessive wear and breakdown. Plus if you are going to go with an after market cold air intake system you need to have your cars computer reprogrammed for that to be effective in the proper manor. All vehicles have been set to work on 250 cfm of air flow. So if your new system allows for more you need to have a performance update done to the cars computer module to take that into consideration. Why spend the hard earned monies on something that you won't be able to utilize to its fullest potential.

Just some food for thought. I can explain more later on this just let me know. My contact info can be found at www.weareoil.com.

Thanks.

The oil on the kn filter is already hard at work wrecking your maf sensor. Go back to paper air filter or you'll be sitting on the side of the highway with your hazard lights on wishing you had a AAA card. You'll need to clean or replace your maf sensor.

You are just lucky to live in a marine climate where it seldom goes below freezing. Removing the factory air box is no big deal, but deleting the temp sensor is. The ECU needs to know what the incoming air temp is in order to regulate the air/fuel mix correctly. I believe the default, sans sensor, is 20C which would really enrich the mixture at 0C.

Zip tie the old sensor to the air filter and see if that makes a difference.

Klaus
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There is no present time, just the past and future

You might need newer plugs or try the next hotter heat range for cold weather.

Phil