Is there an actual idle set screw on the 2.8? I see it mentioned in previous threads but can't find any pics of it.

There is a throttle stop screw, hidden under a cover. Leave it there, unless you want to spend weeks suffering and struggling to set it back where it belongs. There is absolutly never a time when it is okay to change it on a stock engine.

Not even just a weeee little bit

I guess it's back to probing sensors....

...not even a little teenie tiny bit.....

if the idle is off, try adjusting the arm on the TPS sensor with a pair of pliers to get the correct voltage at idle. also, if the set screw has been tampered with simply back off the screw until the throttle blade just barely catches, if doing this then adjusting the TPS is a MUST

I take it your idle is bad?

Which way, high I would guess?

Most likely cause vacuum leaks or bad CTS.

You didn`t hear this from me --but if someone has popped the cap and tapered with it allready try this:

If everything is working properly, no exhaust leaks, no EGR leaks, and
the engine is properly tuned, you can go through the IAC system.

Idle is controled by the IAC valve (idle air control) via the computer and
is not adjustable.

You can go over the system if your not happy with where it is idleing.
Proper idle for the V6 is roughly 900 RPM.

The set screw in the throttle body is for minimum air flow through the
throttle plate which is often misunderstood as the idle screw. Any tweaking
of the throttle stop screw will give the ECM fits. The ECM wants to be in
control of the idle and is not happy when it can't control it. If the
normal
learn limits of the ECM are exceeded, they will be reset to nominal,
causing
an erratic idle.

The IAC and associated passages need to be clean to work right. Remove the
IAC carefully. You can clean it (the nipple) using carb cleaner and a small
brass brush or rag. At this time also clean the throttle palte. Once clean,
install the IAC back in the throttle body and reconnect the IAC wires.

For the ECM to properly control idle, the throttle stop screw must be set
for "minimum air". This is a process that sets the idle with the IAC fully
extended. To fully extend the IAC, jumper ALDL pins A and B together (just
like when you check codes) and turn the key on, but do not start the car.
With the key on, not running, and in diags mode, the ECM will keep
trying to
fully extend the IAC. After 30 seconds or so, pull the IAC connector
off the
IAC *before* doing anything else. This will capture the IAC fully extended.

Now pull out the jumper in the ALDL, and start the car. Typically the
"minimum air" idle speed is in the 500 RPM range. I find the car can bearly
run at 550. So as long as you can get it to idle on its own between 600 &
700 your good. Set the idle using the throttle stop screw. (The engine
should be fully warm to do this.) Now shut the engine off and reconnect the
IAC wires. The ECM does not know where the IAC present position is, so pull
the ECM fuse (or disconnect the battery) for 20-30 seconds. (This will
cause
a complete ECM reset of all learned parameters, including the learned IAC
ones. Then reinstall the ECM fuse.

Turn the key on, wait 10 seconds or so, and turn the key back off. This
will
now reset the IAC to a known key-off "park" position. Now start the
car. The
engine should idle properly under control of the ECM. There are some
learned
values, such as an IAC offset for A/C, etc that need to be learned, but
this
will happen under normal driving conditions. I suggest driving the car
right
away under all conditions. Stop & go, steady cruising over 45 mph, full
throttle, and so on. Pull over a few times and turn the car off, then
restart it. The IAC can only learn X amount of counts with each run
position. If everything else on the engine is in good condition and
operating properly it should be around 900 RPM after coming to a complete
stop with slight variations and improve over time.

Superfast, you forgot to add "hit it with a hammer"

Thanks for the responses everyone. My idle is actually too low. After being completely warmed up, the car just will not idle. Whether it's moving or not, it dips just a little low and then stalls out. When warming up, the idle does not hunt all that bad, maybe a 200 rpm range, which I'm not complaining about after hearing of people have 1000 rpm hunts. Superfast, if I want to raise the idle, what is the best way to turn the set screw after doing all the other procedures? And Chicken, I dont know exactly what you mean by the arm on the TPS sensor. I really dont think this is vacuum related b/c the motor was just rebuilt, meaning every tube was just inspected and hooked up as well as all new gaskets. Any more ideas?

Thanks all

~Ryan

Ryan, If that cap is still in there, you really don`t want to remove it, you have a sensor problem or some other problem as mentioned, I`d look towards the iac, mat, cts. winaldl would probally be your best bet and save some time and coin in the process. Or as mentioned you can hit it with a hammer LOL. If you need help with winaldl mr. wise guy above or my-self will be glad to help .

A Fiero with nothing broken will NEVER need it's screw moved from it's factory position. Never ever ever. The ECM uses it's sensors to compensate. If the idle is wrong, one of the sensors is giving the ECM bad information. You really really don't want to try to adjust the idle with that screw.

the TPS sensor has a little swing arm that is rotated by the throttle shaft, overtime in will go out of calibration ( .85mv if I remember correctly ), simply use a voltmemter or a scan tool to see what the mv is at idle, or key on/engine off - simply use a set of needle nose pliers to bend the arm until it reads the correct mv. - and follow this with cleaning the crap out of the IAC bore and reseting the IAC pintle length to 1 1/8", measured from the point of the pintle to the mating surface of the IAC valve

check the IAT/MAT sensor on the air cleaner. if it is reading ridiculously high, it will lean the mix out enough to cause idle issues.

you can check it with a meter for resistance, best to do it after the car sat overnite so everything is cool and roughly ambient temp. you can use this chart for ref:

let me just cut to the chase..... do you have a scan tool?

------------------
Former West Coast Fiero Employee

New and Pre-Owned Auto Sales Consultant
Power Ford Valencia

http://winaldl.joby.se/
http://www.aldlcable.com/

No, I don't have a scan tool. Do you mean one that just reads codes or does more than that? We made the cable to do the WinALDL but the program would not recognize that it was hooked up to the car. I really dont know what's wrong with that. I'm going to give it another try today and hopefully can get it working.

Are you using a newer laptop ?

A year or so old maybe

The V6 is somewhat sensitive to the throttle body bore being dirty. Over time, a layer of sludge can form around the edges of the throttle plate. This can cause a low idle with a tendency for the engine to quit. You need to make sure that the inside of the throttle body is very clean before trying to mess with sensors and such. If your minimum air screw is still sealed, DO NOT mess with it. If the idle is still too low after a good cleaning, then you need to start looking at sensors and such. A scan tool is well worth the money and will help avoid replacing good components.

------------------
Rod Schneider, Woodstock, Ga.
"You can't have too many toys!"
1988 Fiero GT
1966 Porsche 911
Van's RV-6 airplane-under construction

Can anyone point me in the direction of the scan tool everyone is mentioning. I'm only aware of the cheap ones that tell you a code, is there another type?

Basically everyone uses Winaldl and the cable I assume you made. Done right the cables usually work ok.
Does you LT have a serial port or are you using a usb serial adaptor. Know some have had problem with getting those to work with the cables.

[This message has been edited by Dodgerunner (edited 03-12-2007).]

quote Originally posted by ConvictedRedneck: Thanks for the responses everyone. My idle is actually too low. After being completely warmed up, the car just will not idle. Whether it's moving or not, it dips just a little low and then stalls out. When warming up, the idle does not hunt all that bad, maybe a 200 rpm range, which I'm not complaining about after hearing of people have 1000 rpm hunts. Superfast, if I want to raise the idle, what is the best way to turn the set screw after doing all the other procedures? And Chicken, I dont know exactly what you mean by the arm on the TPS sensor. I really dont think this is vacuum related b/c the motor was just rebuilt, meaning every tube was just inspected and hooked up as well as all new gaskets. Any more ideas? Thanks all ~Ryan

Please - save yourself some problems and DO NOT attempt to adjust the throttle valve stop screw. If you're having idling problems, it's due to some other problem and adjusting the throttle body will just create an additional problem. If the cap is still in place, leave it alone! If the cap is already missing - probably the best solution is to acquire another throttle body that has not been molested and replace it.

First step - behind the battery on the right side of the engine compartment is a large connector. There's an ORANGE wire coming out of that connector that has an inline connector in it. Disconnect that connector, count to 10, and plug it back in. That'll reset the ECM and may solve this problem. You'll have to drive the car for 20 miles or so at varying speeds so the ECM can re-learn your car's best settings.

If that doesn't cure it, your next step is to check the passages behind the IAC valve. That's the bigger "sender" screwed into the throttle body, the one with a 4 wire connector on it. Unscrew it and make sure the passage behind it is clear and clean. If not, some Brakleen and a few pipe cleaners will take care of it.

A couple of questions: does your Check Engine light come on when you turn on the key? Does it stay on when the engine is running?

Ryan, We can talk you through the winaldl, its probally reconized the best here on the forum and the less exspensive way to approach this, after you learn this you will be able to take the guess work out of solving problems with your driveability issues now and in the future, I use an older laptop just for this, DR above and some others can help you with the things needed to adapt to a newer laptop like you have, after that , it shouldn`t be a problem in we/us helping you with the data logs.

Update to this thread, I could not get winALDL to work, it may have been my connector. Anyway, not important, I did it the manual way and probed the ecm with a multimeter. Everything seemed to check out OK, but I decided to play with the TPS voltage arm since the readings for that at idle were on the low end of the spectrum. Sure enough, with a little adjusting of that metal arm, she idles fine now! Thanks everyone for the help!


Edit: sorry for the overdue bump, but I thought I'd take bonzo's advice of finishing a thread!

[This message has been edited by ConvictedRedneck (edited 03-28-2007).]

quote Originally posted by ConvictedRedneck: but I decided to play with the TPS voltage arm since the readings for that at idle were on the low end of the spectrum. Sure enough, with a little adjusting of that metal arm, she idles fine now!

How much voltage do you have now?

if memory serves, it's supposed to be @ 0.45mv at idle

------------------
Former West Coast Fiero Employee

New and Pre-Owned Auto Sales Consultant
Power Ford Valencia

Ya, idle speed on most cars now is controled by ECM. If you move the screw to raise the idle, next time you start it, computer will reset it back to where it was anyway. And then like he said youll spend the next month trying to get it back to where it was in the first place.