All I can see is the IAC vs. coolant temp for adjusting how the IAC actually responds aside from idle. I have no idle problems.

What's going on is that the IAC will open depending on the load increase. Well, this is giving me a sudden hesitation from going lean as that IAC suddenly opens. It feels like a miss. The BLM's are right at 128 when this happens. This only occurs when you are in a situation where you have to push the accelerator moderately to a lot and not at higher rpms (increase in load reading is usually going up to 120-150 to put this in perspective). This happens a lot if you are just crusing around 2000-2200 rpms and want to just increase your speed but not neccesarily change gears and take off.

If you guys have any suggestions on how I can work this out it would be great. I've done searchs and played with the acceleration enrichment up and down. It's really just a problem with that IAC suddenly opening and giving it a boost of too much air.

This is the 89 MAF and I'm working with TunerPro.

 

Best thing to do is if you're really interested is finding a hac, and read thru the IAC stuff ALOT.

There's a slew of IAC stuff.
But, be warned, go especially slowly, and take extremely good notes. Some of the combos of changes, can make for a miserable ride to get to get to the sholder to change chips.

IAC limits, and park positions are generally all you'll want to play with.
TC doesn't include everything in his tdfs, cause you can get into some wierd situations.

 

I had problems with the throttle follower as well. Except as soon as I got past the tps threshold to activate it the car would surge forward. Made driving in traffic a real drag. After tinkering a bit I ended up jsut disabling the throttle follower alltogether, reset the min idle to minimize the IAC counts, and bumped the stall saver up a bit. Engine feels much more linear now. Itll be a bit different for you since you have a manual but you definatly want to get your hands on the hack and look at the stuff for the IAC and tone down the throttle follower a bit.

 

If you haven't seen it or read it yet ....

http://www.diy-efi.org/gmecm/papers/747iac.txt

Although it applies to the 747 it does explain a lot about how GM does stuff and a bunch of this carries over to the 730 stuff.

Tim

 

interesting

very same symptoms are next on my annoyance list after i get the open loop and cold starting down pat and to my liking


my Formula can be a real bear unless a gentle foot is used in traffic and i mean gentle anymore and it wants to jump when trying to crawl along .........

Possibly be related to my surging experienced when the idle is dropping when letting off the gas in the 1300-1000rpm area?
Surge at that area while driving has mostly been tamed by advancing the timing some in the affected areas, which did nothing for the decel surge...

thanks for giving me another project
Jeremy

 

Some masks run additional fuel whenever the IAC is retracting (opening). I looked at the $6E and couldn't find anything of that nature. Greg, you may want to set the max throttle follower (TF) counts to a low number. Once this is done you'll be able to tell if the problem is cured or not.

It may be that you just need to tweak the MAF tables a hair. Changing the MAF tables on a mini-rammed engine is common.

Speaking of TF, I like to set the gain so that the max steps are reached at the same time max TPS is reached. This is typically much slower (less gain) then stock and removes much of the IAC TF feel.

RBob.

 

The 'ole traffic crawl. . . This is actually a defined driveability parameter. As it is I spend a lot of time with this one. Data logs and Industrial Parks after hours & on weekends are your friend.

Start logging and then do the crawl. Try to get the problem to manifest itself over and over, or if possible hold it at that point.

Then look at the data logs. Check for things like stall saver SA, stall saver IAC. Jumps in SA or VE due to abrupt table changes. Look and see what the IAC is doing.

See if the ECM thinks it is at idle and is doing idle control SA. Can also just unplug the IAC. Once the engine is up to temperature and you are at the industrial park, unplug the IAC. This removes it from the equation. See if the problem is better or worse.

RBob.