I was on my lunch break from work today and a cel came on, I figured had time to the car to the dealer, so i dropped it off. They called me later today and said that the intake manifold needs to be replaced due to one of the intake runner's being stuck open. Well i know what a runner is, possibly one of the valves for the 6 ports? does anyone want to help me understand what, and why its going on. I have a 6spd with 48k mi. car ran fine even after cel came on. responses are appretiated.

 

Same thing on this thread

https://www.rx8club.com/showthread.p...ntake+manifold

 

thanks, so what would the cost be of a oem manifold, anyone know? just curious

 

Here's another

https://www.rx8club.com/series-i-trouble-shooting-95/intake-needs-replaced-due-carbon-deposits-%243200-00-a-90945/

 

at 48k miles? $0 to you

 

We have at least 20 oem lower manifolds on the shelf and could sell you some if the warranty does not cover the problem. These are intakes taken off of brand new motors from Japan and never used....but not brand new parts in a bag so there would be a large savings in price over the alternative.

The problem is the APV valve runners either broke off the small metal piece that turns it or your APV motor has failed.

We have built over 300 rx8 motors since the inception and are quite aware of the typical problems under race use. The factory mechanic might not give you the whole answer but it seems to me that just your APV actuator has failed. That is the little black electric motor on the outside of your lower intake. I rarely see the Intake valve sticking or breaking....though the parts are quite small and fragile.

The biggest problem you face...if you keep driving it as is...will be very expensive engine repair, depending on the valve being stuck open or closed. If stuck closed then you will just run rich and possible safe. If open, then you will always be runnin more lean than normal. A quick check of the plugs can tell you this without pulling the whole intake.

There are two other valves that are vacuum activated but to me would not be called an intake runner. These are easier to check. Just follow the two lines from your vacuum box to the brass receptacles and flick the levers by hand, this will show you if they are stuck or not. sometimes the vacuum soenoids wear out and are simple to replace...just unplug and put a new one in. We have those as well.

Let me know if you need any more help.

 

The 5th/6th port could be sticking from carbon. Or it's your SSV (secondary shutter valve). This valve eliminates any air flow to the secondary ports below 4k while keeping the air velocity hi for the primary ports. This helps with low end torque. Anyone who usually has these sticking problems isn't running their rotary through the rpms enough. These valves need to actuate themselves on a regular bases to help keep the more clean of carbon. Sometimes the carbon build up is so excessive the 5th/6th ports sleeves can break when trying to remove the manifold.

 

I had the same problem and had the intake and apv motor replaced. Not that it couldn't happen again, but by using your entire rpm spectrum, you will keep those valves opening and closing and lessen the chance of carbon building up and making them stick.