Hi ya'll. I'm new here and stumbled across the site. Anyhow, I've got a 55' Mercury, but this problem concerns my truck , which is a 96' Tacoma with about 170k on it. I bought a K and N filter a year and a half ago. It made a pretty big improvement in the way it ran and I got better fuel economy, but after about 6-7 months, The truck began to run pretty rough at idle. So I did a diagnostic test and a bad IAC valve came up. So I took the throttle body off and found that the entire throttle body was filhty. The IAC valve was chock full of debris. So I had to replace the valve and clean the heck out of the throttle body. I used Seafoam deep creep in the intake as well. Put it all back together and it ran good as new. I figured that at it's age and mileage, the dirt was simply 10 years worth of accumulation. Anyhow, 4 months later, it does it again- almost dies at intersections and stop lights. Again I take it all apart and find that the throttle body is filthy. Again I clean it and it runs fine. At this point I highly suspect that the filter is letting in way to much poodle poop into the engine. I had properly maintained it, cleaned it, let it dry and reoiled it just as the instructions say, cleaned the seals on the air filter box, and so forth. I've heard this from a number of people with my truck. The throttle bodies on these trucks have tiny vaccum passages, so if they get dirty at all, the engine runs like .... Any thoughts? thanks!

 

I think the downside of these types of filters is well known. They allow more air to pass as well as more crap.

Check yours for tears, separations, cracks around the edges. Check the fit on the air box or other seals. Check the rest of the system for leaks downstream of the filter.

If the filter is passing this much gunk, swap it out to a different one.

 

In engineering there are always trade-offs. Nothing is "free". There is a good reason that Toyota, Ford and everyone else uses paper air filters as OE, the K&N type dont filter very well. Some here, and K&N themselves, will try and blame you for over or under oiling the thing. That is a dodge from the real issue, which you discovered the hard way. One thing you didnt mention is if you cleaned your MAF sensor. A lot of K&N related problems are due to oil from the filter coating the sensor wire.

Jim