Got a question folks. I am contemplating taking my airpump off and the acv. Those of you that have taken off the airpump and acv, how does it idle? My car is large street port and idles very nice with airpump. Not good without it. The AFR changes at idle, of course, without airpump but I have leaned it out at idle and it still idles nicer with airpump. Unfortunately, with airpump on the thing backfires on deceleration horribly. So i think it has to go. Any input appreciated.

 

I presume you are using a PFC. You will have to turn off O2 feedback and possibly tighten the screw under the TB elbow, between the two studs for starters. Leaning it out helps but when the IAT sensor heatsoaks (like when hot starting), it can lean out too much and cause some surging issues (on cars that still have an ISC valve which I presume you have). You really need a datalogit to get the idle just right in that situation.

 

I do have ISC and PFC. I will have it tuned by professional but I just wanted to make sure I can get a smooth idle without an airpump. Honestly I haven't been around a lot of other FD's

 

you can do it ... no problem

 

yea I just raised my idle a little bit and it's smooth

 

doesnt that change the tps voltage when you use that bleed screw? i used the bleed screw that adjusts the throttle plates themselves...the one thats in plain sight

 

if it's not moving the throttle butterflys (and it doesn't), the air bleed screw won't affect the TPS voltage. With the ISC still installed you are less likely to need to adjust those other screws.

if your tuner knows his stuff he will be able to get it to idle smoothly under all conditions with no airpump. How lean he can get it without it occasionally surging depends in part on how much time he puts into it or whether he already has a map that is suited to your setup. If you want it as lean as possible without surging (high 12's if ported and low 13's if unported on many cars) it often takes some careful adjustment of the TB screws and the various correction maps in the PFC. I mean I've personally done it with ISC and no airpump, but it took many hours to get it perfect.

What I do is I reset the PFC (necessary for performing the idle learn procedure) and then reload the map I had in there before. I set the normal idle and electrical load idle both to 850 (or whatever you want), then tighten the air adjust screw all the way and back it out between 1/4 and 1/2 turn. Then I turn off O2 feedback and do the idle learn procedure from the PFC manual. From there you can adjust the idle cells in the INJ map, being mindful that the PFC interpolates between cells as the vacuum reading changes slightly (and it will). Then you've gotta drive the car around for a while because it still takes time for the PFC to stabilize the idle where it needs to be without sticking, especially as the weather changes.

Then if you really want it want it perfect you will have to do multiple cold and hot start tests to see how the AFR's fluctuate, so you can adjust the air and water temp correction tables. On cold starts I try to adjust the water temp map so that it idles at maybe 12:1. Hot starts can be especially tricky because the car will pull slightly less vacuum and is thus affected by different cells in the INJ map. If it idles too lean the ISC will make the idle surge. Yet if you overcompensate on any of the temperature correction mixtures it will run too rich under boost as the weather conditions change.

It's a tedious process. Just let your tuner deal with it as much as he chooses to. It's a lot harder than WOT tuning, which is actually pretty easy on most cars.

 

yea I have a cold start surging. It's literally for 5 seconds only though and then it smooths out. Hot start is perfect and I have no other concerns. I had to raise my idle to like 950 because with a 750 idle on cold starts the car runs rich and fouls the plugs out. After it's warm I could drop the RPM back to 750 and have no problems till the next cold start but it's annoying to keep adjusting so i just left it at 950.

I am running the stock ECU as well so I can't really change anything to compensate besides idle.

 

Are you running stock O2 sensor or wideband? With my wideband O2 and AEM ecu, I simply unplugged my airpump and the car ran as normal w/o re-tuning.

 

holy crap all this tuning just to take the air pump off? i knew i should have stuck to chevy`s j/k

 

^ Yeah, really. Don't understand the fascination with removing the air pump. Its not like it frees up any noticeable HP and you need to replace it with some kind of idler pulley or other band aid so that the belt can retain enough contact with the water pump.

OP - spend some time reading the FAQ and searching. This info is already out there and well documented. No point in adding another redundant and useless thread...

 

Edit

 

Makes perfect sense. If you've removed all other emissions there's no reason to leave it on when there are good alternatives...like an idler pulley, for space, looks and weight. That's not a band-aid anymore than an aftermarket catback is a band-aid for removing the stock exhaust.

 

^In that scenario, yes it does. For some dumb reason, I thought I read "stock port" when I originally read the post. My bad. Probably been working too long today and burning my eyes out...

On an otherwise stock car, it doesn't make much sense.

 

^Agreed. And as disclaimer for anyone searching this subject in the future, please note that the OP is running a PFC. I personally would NOT remove the AP on the stock ECU.
As gracer7-rx7 pointed out, there is no real performance gain, but if your on the stock ECU, there's a risk of poor idle quality and even hesitation on accelaration which (AFAIK) cannot be compensated for without a stand-alone. It will also require purchase of oversized pulleys (which carry their own set of issues) or an idler pulley.

 

I removed my air pump and ran into nothing but trouble with idle issues and car bogging out, the amount of trouble and money involved has convinced me not to touch that air pump again.