IAC and Starting problem...Battery?

slant 6

Member
Out of the blue, my 87 GN with all the regular mods (plus alky) has started acting strangely. I recently changed to a AC 42 plug . Don't know if that has had an effect, because the car seemed to run fine with them for a couple of weeks. And this problem had been occurring before I changed out plugs. Here's the issue:

When I start the car, it turns over 1 turn or so, slowly, and then speeds up and starts. Then when I try to restart, it just turns over and won't fire. However, if I jump the car....it starts! But then, it starts to sputter.

I noticed the IAC was reading 90 plus. So I got it down to about 35 with clockwise adjustments. I also reset the TPS to about .44 and 4.7. Tightened that down.

It was running smoothe and sounded great. I put it in Drive, start to pull forward, and it starts sputtering again. Now the IAC is back up in the 100's. I shut it off. The TPS is now down to .22 in idle. So I reset it again and tightened it.

Now I can't get the IAC to get off of 175. No matter what direction and how far I turn it.

Of course the car is sputtering like nuts.

As far as the battery, I think I have a slow drain going on that I haven't pin pointed. Could a bad battery cause wierd issues? When the car is running, it's getting 13.9 A or so.

Last question. How do you get the IAC back to some base line?

Thanks for any help anyone has.
 
Out of the blue, my 87 GN with all the regular mods (plus alky) has started acting strangely. I recently changed to a AC 42 plug . Don't know if that has had an effect, because the car seemed to run fine with them for a couple of weeks. And this problem had been occurring before I changed out plugs. Here's the issue:

When I start the car, it turns over 1 turn or so, slowly, and then speeds up and starts. Then when I try to restart, it just turns over and won't fire. However, if I jump the car....it starts! But then, it starts to sputter. Could a bad battery cause wierd issues? When the car is running, it's getting 13.9 A or so.

The battery is most likely the problem or the connections. An ignition system is loaded the most while the car is cranking so it may not have enough juice to fire up if it's cranking slower than usual. It still may not cure the sputtering.


I noticed the IAC was reading 90 plus. So I got it down to about 35 with clockwise adjustments. I also reset the TPS to about .44 and 4.7. Tightened that down.


............
Now I can't get the IAC to get off of 175. No matter what direction and how far I turn it. Last question. How do you get the IAC back to some base line?

Thanks for any help anyone has.

You can't do that....well you can but its the wrong way. You will now have to set the base idle adjustment.

Click here: IAC Reset Procedure
 
Make sure when u set the IAC counts that the car is warmed up. as the car warms up the IAC counts will go down until the car is fully warm and they will stop at a certain number, then u can adjust from there.

i had a problem with high IAC counts before and sputtering while car was cold and idling. my IAC would read above 100 for a few seconds, try to drop below 100 and then almost die, after that the IAC went right back up to above 100 to prevent the car from stalling. turned out the mass air flow was bad. next time u start the car walk out and unplug the MAF while its running and see if it runs any better, just a quick and easy check!
 
IAC and Battery

I already performed the function of resetting the IAC. I got it down to about 35-37 on my scanmaster. Car was running smoothe. When I start it back up, the IAC starts at about 50 or so and just keeps climbing again.

I took the battery out and charged it overnight. Put it back and the car immediately starts, but then cuts out again with the IAC showing very high and climibing before the engine shuts off. (Yes, there is gas in the car:smile: ) It will only run for a few seconds. Oddly, I notice the min/max settings on my TPS seem slightly different than what I reset them to. And I tightened the screws snug.

I'm not getting any malfunction codes. I wonder if the IAC sensor is bad. I hate to start throwing parts at it. But I'm thinking the battery is fine. I suspect something electrical. I'm going to put the volt meter back on the car in the AM and see if it drained somewhat again.
 
Yes, I did it with the car nice and hot. Followed the instructions. I get the IAC set, but it resets when I turn the car off and start it back up.
 
Yes. The stupid MAF. It's a rebuilt one. I'll do that. Problem is, I can't keep the car running to unplug the MAF.
 
Figured it out!

Stupid MAF! :rolleyes:

I couldn't start the car to even check the MAF by tapping it, so I just took it off. When I pulled it away from the filter, the screen fell out before I even got it all the way off. I think it was just laying sideways

I had the MAF off a few weeks ago and both screens came out, plus a retainer ring in the same shape. This is a rebuilt MAF with the connector going sideways. You can tell they pull the shell apart and glue it back together, and add a little glue in a couple of spots on the retainer ring.

I decided to put both screens back for the heck of it. I glued the retainer ring in and.....voila! :cool: Instantly started. :) I was then able to set the IAC properly. Setting my TPS was a PIA. Everytime I would get a good setting for WOT, it would be too high for idle and visa versa. I played with it for an hour or more! I felt like an idiot. Finally, when I was ready to give up, I somehow got .46 and 4.58. Yes, I filed out the eyes. What's wierd, is that I have gotten higher on WOT before. Beats me. I'm going to put it on one of those units you plug into the ADL (or whatever) and get a better picture of the WOT.

I'm under the impression that you don't necessarily have to be at 4.55 or more. :confused: Any comments on that would be great.

The battery was low, so I took it off and trickle charged it overnight. Car starts right up, no bogging on the first turn of the crank.

Thanks for the replies and suggestions!
 
glad u figured it out! ive gone through four in the cars life time from when my dad owned it to me owning it. gotta love the advance auto rebuilt unit lifetime warranties:smile:

for the tps i think as long as it is above 4.2 volts it will be fine! ive also had to wrestle with the high and low values before. i think u said that the voltages changed when u reset the IAC. that would be because u were adjusting the throttle blade and when u moved it to a new position it will also have a new low voltage setting since u just moved the blade!
 
oh and it may sound silly but i always forgot to remove my floormat when i set my WOT tps voltage. make sure it is not holding ya back!
 
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