I tried disconecting my air pump today, and there was no ecu code, or rough idle but I lost vacuum.

I went from about 11-13 lbs Hg to 9-10 lbs Hg.
(Note this is at 6200 ft elevation)

Is this normal, or did I oncover another problem?

When I plugged it back in vacuum went back to normal.

 

11-13 hg seems low. i pull 17-19 hg. maybe elevation has something to do with that?

 

It has a lot to do with it. 11-13 is very healthy up here.

 

Anyone have any ideas?

 

When I disconected my Air Pump idle whent crazy also, didn't notice any change on vacuum though, the idle got better after installing a couple of resistors equaling about 1000 ohms and few udjustments.
My only issue after removing the air pump is that my car is running pigg rich on idle/low rpm and I beleive that can only be taken care of with aftermarket ECU's.

 

The only thing I can think of is that the air pump draws in air from the intake causing more vacuum at idle, and when this additional suction is removed, the vacuum pressure goes down.

I don't have the normal idle problems associated with disconnecting the air pump, just a little inconsistent idle due to the loss in vacuum.

Is there anyway to fix this, I don;t think the resistors will work since I think it is a vacuum issue rather than ecu.

 

The small amount of air that the airpump draws from the airbox will not affect the vacuum you get in you UIM. Most likely what is happening is that the ECU recognizes that your airpump is unplugged and retards ignition or richens the fuel mixture.

 

So adding a resistor should work? If so where do I add it?

 

This again! I don't see how the ECU can possibly know that your air pump is unplugged. The ONLY electrical connection to the air pump is via a magnetic clutch, which is turned on and off through the air pump relay. If the ECU is firing a relay to give power to the clutch, how is it supposed to know that you've disconnected it?

jds

 

Without the air pump running at idle, you may run really rich. When you run rich, the fuel can wash the lubrication away from the seals and your compression (and vacuum) goes down.

This happened to me when my fuel pressure regulator failed and was dumping fuel into the intake manifold. Vacuum at idle dropped to ~13", instead of the normal 17-18".

 

Good point. Something else I was thinking was that the ACV directs some air into the exhaust ports and before the O2 sensor. If the airpump was unplugged, then less O2 will get to the sensor and the ECU will read this and lean out the mixture... reducing power.

 

Other than the increased fuel, what was the indication that your FPR was bad? Recently my vacuum has gone down from 15 to 11. The car still runs perfect as before and my boost pattern hasn't changed at all. Just lower vacuum.

 

What will happen to vacuum or boost if the Air Pump hoses are disconnected,...and the DP O2 sensor is disconnected (wire broke off).

 

Nothing realy, I was pulling 17-18 inches before and still do after removing the air pump,
about the 02 sensor, I left it disconected by mistake for over 2 weeks and didn't notice any difference with or without it.

The only problem I have after the air pump was gonne is that the car is running pretty rich on idle/Low RPM.

 

Well, you'll get all of the symptoms of too much fuel -- rougher idle, backfiring, hard hot starts, poor fuel economy.

You can clamp the hose running from the FPR to the intake manifold at idle to check it. If your idle smooths out suddenly and your vacuum increases, your FPR is bad.

 

Here goes, I've been through a bit of this with my 96 RS. A garage that did some work on my car disconnected the wires to the air pump as it was causing a bit of noise when it dumped back into the intake on accelaration. Since then I found out that the air pump DOES report back to the factory ECU (at least on my model) & when the pump is removed the ECU switches into "Limp Mode" Which could explain CSMCanuck's initial problem. Interestingly enough if you remove the O2 sensor the ECU switches to rich-mode which some of the backyard mechanics down here have tried.Either way you're introducing an error-condition into a factory configuration. Personally before I mess with the air pump I'll be getting a Power FC to manage things properly.

 

The (hard) little hose that connects the air pump pipe (on the back) to the pipe coming from the rear of the engine,. broke while taking the air pump off.

I noticed the air pipe (coming from the rear of the engine) blows out air. Why?? I thought the air pump would produce air flow into that air pipe instead of the opposite?? Does this explain "no boost" currently??

 

What did you do with the air pipe(s) coming out from the rear of your engine?? The air pipe that mates with the Air Pump??

 

Interesting...unfortunately here in the States I don't get to play with any post '95 cars

The '93 cars definitely aren't connected this way however. No limp mode at all, it just idles rich and seems generally (at least to me) not as smooth.

jds