Here's a question for you all: Is it at all likely that an air pump that is "bad" could cause the car to run overly rich, not enter closed-loop feedback mode at highway cruise, idle poorly when hot (sometimes it even stalls) and backfire on deceleration a lot? Except for the backfires, the problems remain if I pull the air pump relay. I guess my question is really if there is some way a bad airpump can be causing a vacuum leak or some similar problem that could result in these symptoms.

TIA,
jds

 

Well, the air pump only operate from idle to around 3000 rpms. After that, the magnetic clutch disengages.

On highway cruising, it shouldn't make a difference. However, in the lower rpms, if the air pump isn't working properly, it will idle funny and almost feel like the car is going to die.

 

Keep in mind my highway cruising is at or below 3K for this experiment, as that is when the ECU runs in feedback mode (or at least, that is when it is supposed to do so). I don't know how the air pump could cause it however. I don't think the ECU knows anything is wrong, as there's no error code, but it seems to think it shouldn't be in feedback mode even though it should.

The idle problems sound familiar though!

jds

 

The airpump shouldn't effect the idle or getting into closed loop mode. Maybe a bad O2 sensor. Does it ever start cycling?

 

When the air pump is removed the engine will run very rich , this will cause bad idle. If the pump does not put out any air then the car will idle rich.

 

I don't know why, but the air pump definitely seems to affect the idle. Not so sure it has anything to do with the other problem though....the car never starts cycling, it always runs open-loop...but the O2 seems good, I have an air/fuel ratio gauge, and the O2 output looks fine on that. I also never get the error code that would indicate a problem trying to go closed-loop, which indicates to me that something is telling the ECU it shouldn't be in that mode. What, I have no idea.

jds

 

The airpump definitely affects idle. I had a short on the harness wire that blew a fuse. After I replaced the fuse and taped up the wires, my idle was perfect.

 

I'm not positive, but would I think the ECU is a little smarter than just turning on the air pump at low rpms. I would imagine that speed and other things are taken into account when making the determination. So I don't think the air pump would be active in highway cruising, even at low rpms.

 

to all interested parties: I have an airpump for sale, $100

 

This has been covered a few times. Do a search and check it out. I believe you will get your answer.

 

I don't think so...why wouldn't you want your air pump on at highway cruising speeds? Supposedly the cats will go bad if they don't get air pretty regularly, and at the very least it won't work for emissions purposes....I don't see any downside to running the air pump in that scenario.

jds

 

Are you responding to my original question, or somebody else? I know it affects idle, which is a pretty common question, but I haven't found anything linking the airpump and feedback mode, which is really what I'm trying to figure out. If you have found something different, please let me know.

jds

 

Air pump provides secondary air injection at idle and part throttle. It indeed effects throttle response as well as Air/Fuel. The 02 sensor will not correct the rich condition that occurs when unhooking the air pump. Unless you have an ECU that has been tuned for a deleted air pump you will see a negative effect on performance and drivability. Also side effects will be a miss at idle as well as fouled plugs. I have already been down this road with my car years ago. The main cat will eventually clog if its left on the car without a functioning airpump. Any benefits of a disconnected airpump (less parasitic drag) are counter acted by an overly rich condition. To make guesses that "The ECU is smarter than that" is not a way to give good advice for a guy with a problem. You will get all kinds of answers on this forum. Lots of Newbie RX7 owners who think they are experts already. PM me if you have anymore questions.

 

Hear, hear, Zoom Zoom.

The air pump supplies air to the intake and main cat at idle, cruise, and low speed operation (under 3250 rpm). It most definitely affects idle and low speed operation.

I can't see how a malfunctioning air pump would prevent the car from going into closed-loop unless the stock ecu has a set of conditions where it won't go into closed-loop such as reading an A/F ratio too rich to correct....

 

OK, this is pretty interesting...I'm seeing every one of these things. I know a lot of people remove the air pump for performance reasons, but I guess they've tuned their ECU accordingly.

jds

 

I haven't been able to find anything that indicates that the stock ECU will prevent closed-loop operation under circumstances like that, but I suppose it may be possible. Or, I may have a couple different, unrelated problems. First thing to do I guess is swap out that air pump. It just so happens that I know someone who has a spare lying in their garage.

Thanks to everyone for their help on this thread!

jds

 

Yes, the air pump does need to be active to help keep the cat warmed up.

When my car was stock, I had a problem and I assumed it was the air pump. I disengaged it and drive around to see if the problem persisted. The only problem I had during the drive was the bad idle and unstable at low rpms (either just starting out or slowing to a stop). Highway driving was not a problem (even at low rpms) which lead me to believe the air pump was probably using a map like the ECU (so there are more things that determine when it's active than just rpms).

However, it could have been that during highway driving the effect was just not as noticeable but was still there.

Either way, it's not a bad idea to keep a spare air pump around if you don't ever intend on using a midpipe.

 

Sorry to bring an old thread back but when you say this, you mean like it will bog under 3k sometimes?

Like the rpm's wanna drop?

TIA

 

It should be un-noticeable once the car is moving. But at idle, it will stumble pretty bad trying to stay at the stock idle rpms. All that is needed is to increase the idle RPM a little to compensate (unless you have a programmable ECU).

 

O, so this wouldnt be the cause for lets say you're coming off a stop and the rpm's will fluctuate as your letting off the clutch? causing the car to bog?