i jumper off a and b, turn key to on, wait, unplug iac and the tan wire (mine has no black stripe) and start the car. the check engine light never slows down on the blinking.

help? the high idle makes my car too loud for the suburbs and too pissing me off

 

to set the idle speed, after a new IAC sensor. you are supposed to have everything plugged in and do not jump the diagonstics port. Just slightly press the accelerator pedel start your car for 5 sec. turn off for 10 sec then it should be set. You may have a problem with the old IAC sensor, try a new one out. I just had the same prob. There is a factory idle set screw set at min idle but your not supposed to adjust that. As for the closed loop problem. Mine works without unplugging anything. All you need to do is jump the two terminals that you already did. After the car gets to running temp it will go into closed loops so long as all your sensors are operating correctly. Do you have any codes? If so correct these first and maybe a bad IAC sensor could cause this ... also causing your idle to be to high... or being in open loop due to another bad sensor could cause all this? Just need more info to figure this out for you.

 

Yeah man, if you actually start the car with A&B jumped, you can blow the ecm.

For what it's worth tho, I've got 272,000 miles on my original motor, still have the original IAC, and I've never had to adjust the idle speed. Have you checked for vacuum leaks?

 

it seems to be holding a lower idle every time i start the car now. which is what i wanted....

but i read a tech here about jumpring a and b....

i dont think theres any vacume leaks.

 

Oh you can jump a&b, you just can't do these steps in order:

1. Car off
2. Jump a&b
3. Start engine

That's what can blow the ECM. The fancy computers that service stations use will actually have "built-in" a resistor across A&B, and those fancy computers use the data line from the ALDL. For us home guys, with a straight jumper across A&B, we can't start the car with A&B jumped.

 

TomP:
Are you sure? I haven't had any problems running the car with A & B jumpered when I have adjusted idle. I have performed the idle adjustment procedure on both my '89 and '87 2.8L (5-speed) Camaro. The previous owner of the '89 had messed around with the minimum air screw for some reason and I had to correct it. I followed the procedure from the Chilton's manaul which I outlined in this thread:
https://www.thirdgen.org/techbb2/sho...hreadid=235452

That procedure tells you to start the car with A & B connected and to remove it once the car is in closed loop mode. In my experience (and from what I've read), jumping A & B places the car in Field Service Diagnostics mode. That is why the SES light starts flashing. When the light is flashing 2-3 times per second (i.e. - rapidly), the engine is in open-loop mode. When the light is flashing about once every second (i.e. - slowly), the engine is in closed-loop mode.

(Oh, and just for clarification for those who don't know the specifics about the resistor and data line Tom mentioned. The scan tools that repair shops use essentially connect the A & B terminals with a 10K resistor, placing the ECM in ALDL mode. In ALDL mode, the ECM begins sending data down the data line (terminal E, M on some others, if I remember correctly). Check out the interface cable for WinALDL at it's website to see what I mean: http://winaldl.webhop.net )

85berlinetta2.8:
I am guessing you are following the procedure I outlined in the thread above? (It is the exact same procedure from the Chilton's manual, I just added a bunch of notes to it.)

 

Well; I'm pretty darn sure... although I think I did it once many years ago (before I found thirdgen.org) and didn't have trouble. It doesn't seem worth the risk to me, and I'm not going to do any "testing" on my "production system". It's been brought up a bunch of times; here's one of my search messages where Vader goes in-depth (as usual) https://www.thirdgen.org/techbb2/sho...umper+aldl+ecm

 

OK, thanks Tom. I just updated my idle adjustment procedure thread accordingly.
I changed it so that the A & B jumper is removed before starting the engine (but after disconnecting the IAC so that it is fully extended (or is is retracted?)). Also, the A & B jumper is now re-connected after the engine has been started, placing the ECM will be in Field Service Diagnostics mode, so that you can tell when it is in closed loop. From what Vader said in his post, those changes should remove the chance of damaging the ECM. And as far as I know, the idle adjustment procedure should still work after those changes.

Thanks for pointing that out. I'm glad I didn't have any problems when I performed that idle adjustment in the past. In the future though, I'll be sure to follow the changes outlined above.

 

Yeah, it freaked me out too; I swear I've started the car with a&b grounded, but I never will again!

I checked that procedure list against my GM book, and the Chilton's procedure is pretty accurate (with the same bad-for-us indication of leaving A&B jumped)... but, and this may help your car, for the 2.8, my book doesn't say to disconnect the EST bypass connector. It says that's only for "5.0 and 5.7". Also it says for a 2.8 with an automatic, it should be 500 RPM in drive and 600 RPM in neutral (or 600 RPM in neutral for a manual car).

 

so i was good to leave a and b jumped

 

According to the service manual, yes. But according to Vader (and a few other guys on thirdgen.org), no; it can damage the computer. I'd say if you have to do it again, pull the jumper, start the motor, and then put the jumper back.

 

I did it yesterday and followed the proccess provided by linux and adjust my idle speed and the tps. Now the car is felling real good. I just got a problem to get the car in closed loop, but when i put the car in D it went to closed loop. That step is not mentioned there. Also the TPS sensor has three wires there and i found out on chilton's manual that u have to put the leads on wires " A " and "B "...

 

i think my car is acting funny, someitmes when i start it it idles at 1400 stedily. sometimes at 800 ad then down to 600 when its warmed up.

pissing me off

and im still getting soot