I dont have the base, only the SR runners and plennum.
I am working on the IAC adjustment right now, but cant get it to idle lower than 900-1100 rpms ( in park) and 700 in drive.
When setting the base idle I can get it to 450-500 rpm, but with IAC in its goes to 900-1100 area

SO will a new chip change this?
AND how much can I gain from a chip, when i dont have acces to a dyno?
all mods are;

• Super Ram plennum and runners
• BBK AFPR
• LPE LT headrs and front Y
• Borla cat-back
• No cat ( straight pipe)
• AIR delete (breathless performance)
• TB bypass
• 160 T stat.
• K&N w. Cut lid

 

I had to get a custom chip when I installed Super Ram.

 

Lars,

If the idle is too high, even though the min air is correct (400-500 rpm), then you must be operating outside of the normal conditions to enable the idle PID control.

When in PID control, if the rpm is greater than commanded, the IAC will close which should bring the rpms down to the target rpm. This should still be working.

Make sure the tps voltage is correct (0.54 volts) but usually less than 0.63 or so will still work.

Also make sure the min air is correct.

I suspect you still have too much min air and this is affecting the Warm IAC park position table, when not in PID control.

This is a table that sets IAC counts directly as a function of coolant temp, when outside of PID control. If you have too much min air then you will idle higher than normal for a given number of counts.

Here's what the table looks like (taken from an 86 auto trans bin AANM)

Warm IAC Park (Steps) Vs. Coolant Temp.

Deg C Steps
-40 145
-16 145
8 113
32 90
56 80
80 65
104 50
128 50
152 50


Closed Loop IAC Target RPM Vs. Coolant Temp.

Deg C RPM
-40 1050.0
-28 1050.0
-16 1050.0
-4 1050.0
8 1050.0
20 950.0
32 900.0
44 750.0
56 625.0
68 625.0
80 625.0
92 625.0
104 625.0
116 625.0
128 625.0
140 625.0
152 625.0

 

Thanks.

I was affarid that the high idle was a vac leak?
BUT when I can get it to idle at 450rpms no problem (setting base idle) this isent the problem right?


I have only tried to set thw IAC, I will set the TPS tomorrow...

Toy set IAC first and the TPS right?

 

If the min air is ok, then start with the TPS voltage.

If the TPS is > 1.17%, then throttle follower mode will be enabled causing the throttle position to add counts to the IAC at a rate of 1.5 steps/% tps.

There is also a multiplier which seems to make this effect more pronounced in park or neutral. This fits what you have described.

Check the tps voltage with the car running if you can. My tps tends to go up about 0.02-0.04 volts after the engine starts.

 

When you say Min air, you mean base idle set to 450 rpms, AND the IAC pintle fully retractet and disconnectet?

 

Yes. (I think the pindle is actually extended, when the IAC is fully closed at 0 counts, but you get the idea)

 

I think what messes most people us with the IAC adjustment is you need to somewhat forget the recommended 450RPMs the manuals state with a modded up motor.

Here is the way I have always done mine.

Rule 1: when everything is set you want 90% of the air required at idle to be coming through the throttle body and only 10% through the IAC.

I do this by disconnecting the IAC, and opening the TB to the about 90% of the desired idle. To make things simple, lets say I want 1000RPM desired idle. So I would open the throttle body till car idles at 800rpms. Then I would plug in the IAC and with the chip adjusted to the desired idle also of 1000 the IAC will add the other 200rpms by opening the IAC.

What happens is most people NEED to have a higher idle than they realize with a modded up car. (Yes a car will idle at 700, mine even will with a 700 lift cam, but its NOT good.)....So what most people do is they set their idle like the manuals say at 400rpms or so, but they really require a safe idle of ~800-900rpms. You see this base setting without the IAC is only about 50% or less of the amount that I said earlier. As a result the IAC will snap entirely open and this is how you get the hunting idle and other problems people have.

In the above scenerio, you want the idle to be adjusted in your chip to the desired idle setting. Otherwise the ECM will be telling the IAC that the car is idling too quick and it will try to close the IAC to lower the RPM, which you will have set too high.

Remember the system is a closed loop type system.....the car will try to maintain whatever idle is set in the chip. If the idle is too low it will open the IAC, if it is too high it will close the IAC.

The key is to only allow the IAC to have about 10% of the control of the idle, 5% if you have a good handle on how to set it up....

This is a very tough concept for people to grasp, but its quite easy if you break it down like I did above. What you don't want is the IAC to have too much control, especially with a cammed car - because of just the inherent characteristics known as "loping" a cammed car has, the IAC will be trying to stop this loping and it will swing violently until the car stalls.

Through this entire setup, the TPS should also be set - AFTER the min idle is make to keep it at a reasonable setting .58 is where I usually have mine.

Hope this helps!

 

Thanks.
Since I have the stock cam, I would think that a 700rpm (in park) is possible with out any trouble, OR would i need it a bit higher even with the mods I have?

 

I installed a new chip and had my idle set to 700. I have the stock cam and heads with 1.6 roller rockers and a few bolt ons. I have a BBK 52 mm and catbacks. You setup is almost identical to mine. I think 700 works fine for an idle with a super ram and a stock bottom. I set my timing to 10 degrees. Installed 24 lb injectors and set my fuel pressure to 40. I had to mess with it a little to get it running well. I got my chip from FASTCHIP. I guess that added a few more hp. I really don't think the stock chip will work well with a Super Ram. But ask someone who knows more about this. Sprecht du Deutsch?

 

you should be fine in that range with your mods. I was just generally speaking with my example above....I know lots of people have this problems and its due to the above.

I personally set my idle where my oil pressure is a little higher, I don't like to see my oil pressure fluctuate at idle, but then again my setups is much more modded, and hence needs to have a higher idle.

But the 219 cam that many run is not a small cam; its much larger than most people realize - and a little bump in RPMs will make the idle, oil pressure, and behavior a little better in most cases.

You can offset the idle problems a little with more base timing, but essentially what your doing is adding more timing across the ENTIRE timing map, not just idle rpm areas.