I've been getting code 35's for a while, and I'm finally starting to try to find out where the vac leak is. I replaced both the TPS and the IAC in the winter. I also have one of oliver's Dashscan II units so I can look at sensor values and such while I'm driving. Earlier today, I saw that I was getting a code 35 while I was stopped at a drive through window, so I looked at other things, idle was around 975-1025 changing slightly over the couple min I was in neutral, and the IAC was at 0.

While spraying carb cleaner around today to try to find the vac leak, I noticed that the plug on the throttle body screw was missing. So I played around with the screw. It turns out that this screw was holding the throttle open, the TPS value I was getting on my dashscan was .98 at idle, and I have been getting this value since I replaced the TPS in the winter, I could adjust the screw and watch this value go down to .80. I set it to where it was originally, at .98, took off the air tube, let the car idle again, IAC was at 0 steps again, spray some carb cleaner in the throttle, the engine dies... so the throttle isn't closing all the way, is it supposed to? The IAC is working properly, I put my finger over the hole while the IAC was at 0 and there wasn't any suction on my finger and there was no change in the engine.

I start the car up again, I go over all the vac lines with carb cleaner, the intake gaskets, everything but the ERG tube (I replaced that last summer, didn't want to spray something flamable on the EGR tube). No change in the sound of the engine while I was doing this.

So I'd know a previous owner messed around with the throttle adjustment screw, since the blocker plug was off of it, now my question is what's the best way to reset it? Should it let the throttle close all the way? Is there a certain TPS value I should be looking for while setting it? IAC counts? If I end up adjusting it by looking at the IAC counts I don't really know if air is getting into the engine from the throttle or from another vac leak do I?

Thanks for any input, I am willing to do whatever work, whatever reading to figure this out. Oh all the other info that might be ofl help, my BLM has been at 138, my car wants to stall when I first start it up from being cold in the morning until it goes into closed loop mode, I'm about to replace the O2 sensor, I think it might be bad and the computer might be learning false values for the BLM, the exaust smells rich when it wants to stall on the cold startup, and it runs great once warmed up, no hesitation or anything. I replaced the air charge sensor and ECM temp sensors a few months ago. I'm also getting the slightly floaty tach, so I'm making a new tach filter and am going to replace the ICM w/in a week or two. Timing is set properly, although with the aldl terminals jumpered the timing mark does float around a degree +/-, which is why I'm going to replace the ICM.

Thanks again,

-Jeff

Oh I've also been thinking about replacing the MAT sensor, but only have so much money every month I can spend on sensors/parts/test equipment. I recently bought a vacuum gauge but haven't had a chance to hook it up yet.

-Jeff

I got this from the 3rd Gen. website. I adjust it this way. It works.

Tools needed:
Screwdriver
Paper Clip
Small Punch

Take the paper clip and open it up and form it into a big "U" shape. Insert the clip ends into the ALDL in the 'A' and 'B' pins.

Turn on the ignition, but don't start the engine. Wait 30 seconds. Now, go remove the connector from the IAC.

Start engine. You are now going to adjust "minimum air". There is a screw on the side of the throttle body. This is what needs to be turned to adjust minimum air, or more commonly known as "idle speed". It comes from the factory with a protective metal cap over it. If the cap is still there, use a small punch to knock it out. Set the idle speed to 450 rpm, rotating the TB screw clockwise to raise rpm, and counter-clockwise to lower rpm. Once the idle rpm is set, turn off the engine.

Re-connect the connector onto the IAC. Start engine. Idle speed is now once again governed by the ECM, but your idle should be smooth and steady, approximately 600 rpm in Drive (for unmodified cars).

If you set an SES light by having the IAC disconnected, then after shutting down the engine disconnect the negative battery terminal. Wait 5 minutes. This will clear the ECM of all trouble codes. Re-connect the battery and drive the car for 20 minutes to allow the ECM to relearn your driving style.

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3.4L S/C 87 GT www.fierosound.com
2002/2003/2004 World of Wheels Winner &
Multiple IASCA Stereo Award Winner

I don't know what the correct way to set a port injected motor is.

I'm told that port injected engines should have a hot idle of about 30-35 steps on the IAC with no load on the engine. (Automatic in park. Manual out of gear.) I haven't worked on one in so long I can't remember for sure.

People f'ing around with the idle stops on EFI engines is common. Even many so called professionals seem to think adjusting the stop is going to fix whatever ill they think the car has. All it ever does is cause problems for the vast majority of cars they mess with.

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The only thing George Orwell got wrong was the year.

The Ogre's Fiero Cave (It's also at the top of every forum page...)

quote Originally posted by theogre: People f'ing around with the idle stops on EFI engines is common. Even many so called professionals seem to think adjusting the stop is going to fix whatever ill they think the car has. All it ever does is cause problems for the vast majority of cars they mess with.

Yeah everything I've read says NOT to mess with the screw... but since the cover's gone it would be stupid of me to think that a previous owner didn't mess with it...(and just in case he reads, I'm not blaming the guy I bought the car from, it seems another previous owner may have done some other strange stuff with this care including putting an alternator with a 4 groove pulley on it, causing many belts to tear up and break before I noticed the 4 groove pulley where a 5 groove pulley should have been...)

I should also add that this is a V6, last summer I installed a crate 3.1L engine to replace the 2.8L that was in the car when I bought it earlier in the summer. I used all the fiero intakes and accessories and such, 3.1 heads, the injectors that came with the 3.1, fiero fuel rail and wiring and everything.

The idle is smooth not eradic or anything when the code 35 pops up.

-Jeff

I have always closed the the butterfly all the way then start turning the screw till it just starts to move. This will keep it from binding and sticking. Then I put my finger over the IAC hole and make sure it will idle.
You will need to remove the rubber intake tube.
Good luck.

Read this artical it is pretty good

well I just found an intresting thread in the archives:
Topic: How do I adjust my idle?
https://www.fiero.nl/forum/Archives/Archive-000001/HTML/20040223-2-043469.html

A few intresting points brought up:
Posted by Denny:
"I always say that there is no adjuster, since that's the 1st thing lots of shadetree mechanics will go for, before they make sure everything else is working properly.
Point is, you shouldn't have to screw around with that setting. If the previous owner did, I'd find another TB."

Posted by Jazzman:
"The ECM controls the idle by adjusting the air flow through the IAC valve. This air bypasses the throttle plate by way of a tube that goes from the bottom of the throttle body to the manifold near the distributor.

The IAC screws in to close off air flow and drop the idle, and screw out to increase the idle. It does this in discrete steps since the IAC is a stepper motor. If the ECM runs the IAC all the way down to zero steps and the idle is still high, then you either have a vacuum leak or someone has jacked with the factory idle stop screw. This screw is on the top of the throttle body, on the throttle cable side. In the picture posted above you can see the boss next to the cable, there's a circular plug to prevent tampering with the screw.

To properly set this requires using a scan tool to see the steps being commanded by the ECM and adjusting the stop until you see 16-20 steps with the A/C and radiator fan off. If your TB shows signs of having been tampered with, you can go ahead and rule out a vacuum leak by screwing the stop out, counterclockwise, to fully close the throttle plate. If the engine continues running, you need to find out where the air is coming from."

Earlier this evening I closed off the IAC with the ALDL paperclipped, disconnected the IAC's plug, disconnected the paperclip, and started the car. It ran with the TPS sensor showing .98, and then I started adjusting the screw... eventually the engine cut out, and the TPS sensor was showing .74. This is leading me to believe I never had a vac leak, or if I do it's so small it's not letting in enough air for the engine to run. I guess I'll try JazzMan's method for setting the screw, or I'll start looking in the mall for a new TB...

-Jeff

after I bored my throttle body, I had to reset my idle screw. what I did was just cover the IAC hole with my thumb, and adjust the screw untill the car would idle at 500 rpm. I had to let go a few times to keep it from stalling, but it seemed to work. but anywasy, yes, the throttle plate should never be FULLY closed. some air has to get by to let it idle, and the IAC cant let enough thru.