I was told that the screeching is probably caused by the air pump,but I checked the auto parts store and they said there was no air pump listed for an FD so can someone explain.

 

Parts store doesn't carry parts for an FD (for the most part). I think you can buy simple things like rear brake pads and washer fluid.

 

your going to have a hard time finding almost any part for this car at an auto parts store . use the "for sale" section of this forum and pick up a used air pump for $50.

if you really want a new one, you can get one from mazda for well over $1000 .

 

I've got a good used airpump if you're interested

 

First find out if the airpump is the problem. All you need to do is disconnect the electrical connection going to it and take the car for a drive. It will idle like crap, but if you don't hear the noise anymore, then the airpump is going bad. If you do hear the noise still, it's something else.

Diagnose the problem before you try to find replacement parts (that might not need to be replaced).

 

Mahjik is the man!

 

ok what do you have to do to remove the air pump all togeather from the car
the car still has the factory ecu if that helps

 

Greddy offers a kit. it skips the air pump as far as belt routing. Then just undo the three bolts that mount it, undo the quick release connection, and undo the air connection at the back. Lift her out. Be warned that running without an airpump can clog your cat. But that gives you an excuse to go with a midpipe! Check out rx7store.net for the pulley kit. Here's a link: http://www.rx7store.net/index.asp?Pa...ROD&ProdID=270

 

thanks guys

 

but if you remove it then i believe it is gonna mess with his idle and stuff to, right.

so he can take it out and there will be no problems?

 

Yes it will mess with the ilde abit. I tried it with mine and im hoping the apexi fc has a feature to turn off the airpump all together on the electric side.

 

is there any way that you can trick the computer into thinking that it is still there and working ?

 

A resistor should work.

-Max

 

You've got it backwards. The ecu thinks the air pump is there and working, whether it is or not. THAT is why the idle is often too rich and lumpy after removing the air pump with a stock-based ecu.

It's not an issue with the PFC or other programmable ecu, because you can simply lean the idle range cells back out to attain a smooth idle.

 

It's not the computer that's the problem. The ECU expects the extra air from the airpump to be going, so the idle mixture is richened. Without the air from the airpump, the mixture at idle is too rich and causes a very lumpy idle. There are two ways to fix it:

1. Get a programmable ECU and adjust the idle mixture
2. Increase the idle up to around 1100 rpms (on stock and rechipped stock ECU's)

 

thanks guys no wonder they call this the mother of all fourms

and sorry for the hijack of the thread
will try to wind up idle

 

mahjik couldnt you adjust the secondary throttle or the other little screw under the throttle body to allow more air in and that would lean the idle back out. would that work to fix the problem,

i want to remove my air pump because it is dead weight and really serves no purpose but i am not gonna take it off if it is gonna give me crappy idle because that just sucks i hate that surging crap.

can you give me any insight on my theory.

Thomas

 

This brings back the question I asked a few weeks ago. According to the diagram in the FSM, the airpump/ACV does NOT put air into the intake.

The FSM shows four ports on the ACV: airpump input, main cat output, exhaust output, and the blowoff that goes back to the airbox. Here is the diagram:



So what causes the idle problems that most people report with a removed airpump? Obviously the O2 sensor will read a richer mixture since the extra air in the exhaust from the airpump is gone. This leads me to beleive that the ECU would lean out the engine, but most people report a very rich idle, which contradicts my theory.

 

well the air pump sucks air from the intake filters doesnt it.

 

I left my airpump connector off for a while now with idle at around 1100rpms with stock ecu and going to remove the pump soon. I must say it does smell alot worse without the pump. I'm just wondering would I need aftermarket pullies or just need to buy a new belt for the removal?

 

Yes, that's kind of the problem as I don't think this topic has really been explored. We do know that the ECU doesn't get feedback from the airpump so trying to use a resistor does nothing. I need to go back and look at the ACV, it does have a filtered port to the LIM but I'm not sure if that feeds air into the LIM or not.

However, it's quite noticeable when running without the airpump on the stock ECU and trying to maintain a 750-800 rpm idle. You can test this by disconnecting the airpump electrical connection and driving around.

 

It's simple, really. The airpump doesn't inject air into the intake manifold - just the exhaust. The air either goes to port air (into the exhaust manifold), split air (to the main cat) or relief air, which goes out to the airbox.

At idle and light cruise, the air pump is injecting air into the exhaust manifold. The ECU uses O2 feedback to set idle and cruise mixtures. Mazda realized that the output from the oxygen sensor would be wrong with the extra air that's pumped in to the manifold - the extra oxygen will increase the O2 sensor's voltage output past where it should be.

So, Mazda had to compensate. The stock ECU looks at the O2 sensor voltage, and if the air pump is putting air into the manifold it knows to subtract out some of the voltage to get a proper reading. The thing is, the ECU doesn't know if the air pump isn't there. If you remove the air pump, the O2 sensor will be giving a correct reading back to the ECU, which it promptly subtracts some of the value from and injects fuel based on the reading.

You end up with an incorrect input to the ECU, so it gives an incorrect output. It's just that simple.

If you have a stock ECU or a chipped ECU that runs poorly with the airpump not hooked up, in theory the mixture can be tuned back to where it should be with something like a Super-AFC. All you'd need to do is tune idle and light load.

Dale

 

Yes, but in that case the ECU would be subtracting based on a preconcieved notion of air from the airpump showing a higher reading at the O2. You would think in this case, as afterburn27 mentioned the ECU would lean out the car without the airpump (i.e. removing the missing air from the O2 reading which wouldn't exist). The car seems more "rich" without the airpump than it does lean at idle.

 

so might this work?

 

A wideband before/after would tell you if it's really richer or leaner. To me, it seems leaner, just from what I remember of messing with the idle mix screw on FC's. Rich sounds bogged down and "fat", lean is "stuttery". Rotaries typically like a rich idle, but not a lean idle.

Regardless, the O2 feedback is the reason for rough running without the air pump. Doesn't really matter if it's lean or rich - it runs crappy .

Dale