2.8RS

iTrader: (5)

I got my TPS adjusted right. The motor idles about 1700 and when I start it up it goes up to 3500. Is there anyway to get the idle back down?

2.8RS

iTrader: (5)

bump

firstfirebird

iTrader: (3)

You checked vacuum? There isn't a way to change the idle (not like a simple one like a carb). Your Idle Air Control (IAC) takes care of this, you have something else besides your TPS going on.

2.8RS

iTrader: (5)

The idle is nice and and smooth and I've checked for vaccumleaks and never found any. I'm not getting any codes either.

Street Lethal

iTrader: (16)

This sounds like a classic case of a sticky IAC. Remove the IAC, better yet, remove the entire throttle body, and give it a good cleaning with some carb cleaner. Try not to damage the IAC's pintle, but be sure to remove all of the crud inside, which is causing the obstruction. Take extra care, don't just spray the solvent everywhere with the sensors still intact. Dis-assemble, then re-assemble, and don't use the old gaskets...

syko

Where would you get new gaskets then? Could you point me to somewhere I can buy them?

bobdole369

LOL 2.8RS this happened to me today... I bet you unplugged the IAC connector to get it out of the way when doing the TPS. When its unplugged it idles WAY up there and nothing will bring it down. Plug it back in or check the connector or wires for breaks.

Its the other connector on the TB, the top connector, 4 pins roundish.

2.8RS

iTrader: (5)

It's plugged in. I took off the throttle body and UIM to replace the thermestat today. I'll look at the IAC tommorrow. Would a code come up for it?

Street Lethal

iTrader: (16)

A lot of times we tend to assume that the battery was disconnected before any connectors are unplugged. If the battery was still connected though, you might want to disconnect the battery for a few minutes, then reconnect, and allow the BLM to relearn things accordingly. You migh have thrown the ECM for a "loop"....

As for the gaskets, I always order mine through my local Chevy dealership....
----------
Also, no, a code will not be prevalent with a sticky IAC....

2.8RS

iTrader: (5)

Cleaned out the IAC as best I could and unplugged the battery again. Instead of idling at 1700 its probably 1600 now. What should our motors idle at. I want to fix this so my motor doesn't eat up so much gas at idle since I'm stuck in rush hour alot.

firstfirebird

iTrader: (3)

According to the crappy factory tach, about 700RPM in drive.

Bazookajoe254

1986 Firebird 2.8 MPFI

I wanted to try to reduce the idle a bit since my Hayne's book said about 450 for a manual. Thought that was pretty low but since I'm usually around 950-900 idleing, I figured I'd see what good I might be able to do.

I pop off the thin factor metal cover that hides the screw, and I adjust it. The plate that should rest against it didn't move back with it, the valve was sticking.

Figured I should clean out my throttle body, went down to Advanced, got some Fuel Injection - Intake and Manifold cleaner, an aerosol kind. Get home, sprayed it, wiped it, spray it, wiped it...over and over. This thing was so amazingly dirty there was black liquid just streaming out after every spray. I think it was the first time it'd been cleaned in it's 21 years. So I've got the inside of the TB looking like new and the plate still doesn't exactly want to sit on the stopper. I thought 'I guess thats ok, it's still cleaner and better off than it was.'

Wrong.

I went out for the night and now I'm sitting in traffic idleing at about between 1600 and 2000. I don't want to burn off all this gas sitting at lights so I would shift into gear, that would drop the RPMs and when I got down to about 1000 I'd stick in in neutral again and I'd be good off still I started moving. I noticed (example): I'd drive over a bridge at about 1300 rpms in 5th gear. Going down the other side I just put it in neutral and normaly I'd just roll down at the usual 900ish rpms, but no, once I put it in neutral my rpms would climb back to 2000 and sit there until it was in gear again.

I could actually use it as a cruise control (my car doesn't have it) because I could go about 40 without being on the gas in 4th gear and stay there.


Long story short, my good idea turned into something not good.
IAC? TPS? I'm not sure. Maybe I gunked something up wiping down the inside of the TB.

Any thoughts?

Thanks ahead of time for going through my long story.

Street Lethal

iTrader: (16)

Wrong is indeed. When cleaning your throttle body's linkage, you need to follow up that carb cleaner solvent with some WD-40. Otherwise, it will continue to remain obstructed (despite giving a clean appearance). The linkage need's to move freely....

2.8RS

iTrader: (5)

My throttle body is cleaned out already. So is my intake. The TPS is good because I just replaced it and adjusted it to the right voltage, but to do that I had to open up the throttle more. The car runs great and idles smooth. It's just up to 1700 or so. I look around on the web and I read that it could be the IAC. I just cleaned out the top plate of the TB today. I took out the IAC and with what my Haynes manuel is telling me where the sensor should be, I figured that the IAC is shot so I'm going to go get a new one in a minute. If that doesn't solve the problem then I can only figure that having the TB so open for the TPS is the issue.

Bazookajoe254

Yep, I just got to your post and I've allready fixed the problem but thanks for the reply, you were right. First thing I did when I got home last night was coat the spring and all with wd40 and hope it'd be free in the morning.

Ran into another problem I'll share. I was still having some trouble with the idle so I started to take out the IAC... snap. The threaded end broke off and stayed right where it was. Took me 2 hours to get it out but I finally got a Roto-Zip, slowly wore away at one side of it until I was down the the bare minimum and chisled at a side of it. It broke loose and after some more WD40 I was able to twist it out.

I'm 17 and that was officially the most work I've had to do personally on my car where the actual engine was somewhat vulnerable and it came out ok, so I'm on a success high right now lol.

bilms01

There is an "idle learn process" for this problem when the IAC in disconnected the ECM forgets where it actually is.

The ECM will relearn and reset the IAC when the vehicle is at "normal operating temp AND driven at speeds over 40MPH. I have had to drive them for 3-5 miles at open road speed to get the system to 'relearn"

2.8RS

iTrader: (5)

I replaced the IAC and I just got back from a drive and got up to operating temp and rode at 40mph for about a quarter mile. The idle is the same as it was. 1700 and smooth. I think that this may be from the TB being open due to the TPS.

EDIT:
I read the tech article on the homepage and I really don't understand how I am supposed to adjust the IAC. I read that I have to set the idle speed but the will throw my TPS off. I am kind of stuck in this situation.

Also could having a bad EGR system cause this? I have a good vavle but I think that the solenoid is shot. I've been putting getting a new one off because of price and I think that I really don't need one.

firstfirebird

iTrader: (3)

I have a selenoid if you need it, but since it's been off my car I've had no problems. EGR doesn't do anything at idle, so I wouldn't suspect it in your case.

2.8RS

iTrader: (5)

Ok thats what I thought. I read a thread somewhere else for an answer to my problem where they said that.

bilms01

Maybe these pages will help. They are from my 89 F Body GM service manual.

That screw is for setting minimum idle air with the IAC off (at 0 count as commanded by the ECM). firstfirebird is correct when he says the IAC controls idle speed. It is not advisable to adjust the screw unless the throttle body is replaced with a reman TB. It is used for adjusting MINIMUM idle NOT curb idle.

2.8RS

iTrader: (5)

I am clueless on how to fix this. Can someone tell me how to set whatever needs to be set to get the idle down.
Thanks

firstfirebird

iTrader: (3)

Did it start AFTER adjusting the TPS?

Street Lethal

iTrader: (16)

Although there are various ways for me to explain, I'm just going to post Vader's explanation, as he is very thorough, and all of us initially learned from him anyways;

Throttle Minimum Air Position Tools needed:

1. Torx driver # T-20
2. Paper Clip
3. Small Punch
4. Tachometer

GENERAL NOTE: The engine should be at normal operating temperature before performing any adjustments. Never rely on the dash mounted instruments for diagnostics and adjustments. The oil pressure and temperature gauges and the voltmeter and tachometer just aren't calibrated accurately enough for diagnosis, but are a relative indication for monitoring the vehicle while driving.

For this adjustment, the transmission will be in DRIVE while you're under the hood. You will need to securely set the parking brake and block the drive wheels. It would also be a good idea to have an assistant hold the service brake while you perform the adjustments.

In order to successfully complete the adjustment, the IAC air passages and pintle need to be clean. The throttle plates and bores need to be clean as well. If this is not the case, you'll need to remove the air cleaner from TBI engines or the intake air bellows from TPI engines to gain access to the area to be cleaned. A spray-type carburetor cleaner works well for this. Cleaning the IAC passages on a TPI/MAF engine will set a DTC, but we'll be clearing that later. With the engine idling, direct the spray cleaner in to the IAC air passages and around the throttle plates. Shut off the engine and continue cleaning the throttle plates by opening the throttle manually. Once everything is satisfactorily cleaned, replace the air bellows on TPI engines. Many times, this alone can solve IAC/idle speed problems.

If this doesn't solve the problem, you may need to remove and clean the IAC stepper motor. If the IAC appears to be clean and functioning properly, continue with the adjustment procedure.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Idle Air Control Cleaning

You can remove the IAC and service it. Remove the electrical connector from the IAC. Unscrew the IAC unit from the throttle body.

You can gently rock the pintle back and forth and allow the spring to extend it until it comes apart in your hands. Clean everything with lint-free cloths and a mild solvent. Harsh solvents can affect the insulation of the stepper motor coils. It's generally the dirt and buildup on this worm shaft that causes sluggish IAC operation.

When the worm gear on the pintle shaft is clean and dry, apply one drop of clean light oil to the shaft and work the pintle back into the rack gears of the motor by the same rocking motion. It takes a while to get the pintle back into the worm gears, but you'll get it. It is important to get the pintle fully retracted into the housing so that the pintle is not forced against the gears when reinstalling the IAC unit in the throttle body.

While the IAC is out, clean the air passages in the throttle body. The orifice in the TB where the IAC resides is the seat that the IAC valve closes against, and it can accumulate a lot of carbon, dirt, and debris. The easy way to do this is with carburetor cleaner and a small stiff brush.

When everything is clean and dry, replace the gasket if it is damaged, apply a little anti-seize to the threads, and torque the IAC to the proper specs. (13 ft/lb for '85-'89 , 30 in/lb for 1990-on.) Proceed with setting the TPS and minimum air position.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Locate the ALDL connector under your dash panel, in the driver's footwell area. Remove the plastic trim cover (if it is still there).

http://216.121.161.76/files/ALDLPlug.jpg

Cut and form a paper clip into a "U" shape. Insert the clip ends into the ALDL in the 'A' and 'B' sockets.

http://216.121.161.76/files/ALDL.gif

Turn on the ignition, but don't start the engine. This will force the ECM into its diagnostic mode. Wait 30 seconds to allow the IAC pintle to fully extend. Under the hood, remove the electrical connector from the IAC, then turn off the ignition and remove the paper clip jumper from the ALDL. With the IAC pintle fully extended (closed) all idle air will be controlled by the position of the throttle plates. Some manuals indicate that the EST bypass connector should be disconnected for this procedure, while some make no mention of it. While timing is a factor in idle speed, the EST should only operate as a function of engine RPM, temperature, and detonation sensor inputs. To remove all doubt, disconnect the EST bypass connector is your car is so equipped. Some TBI and V-6 engines do not have this bypass connector, and therefore must be set with no regard to the EST system. The EST can be bypassed on some cars by grounding the diagnostic terminal at the ALDL and continuing with the procedure, but the fuel mixture will be skewed to the rich side, affecting idle speed as well. In any event, the minimum air position idle speed range is wide enough to allow for some variations. As always, it is best to consult your service manual for the exact procedure for your system.
Locate the Torx screw on the left side of the throttle body. It may be equipped with a protective metal cap from the factory. This was intended to discourage adjustment. If the cap is present, use a small punch to knock it out. Once the screw is accessible, start the engine and place the transmission in DRIVE. Adjust the throttle stop to obtain 400 RPM with the transmission in "DRIVE" on an automatic transmission car, 450 in neutral on a manual transmission car, rotating the Torx screw clockwise to raise speed and counter-clockwise to lower speed. Once the idle RPM is set, place the transmission in PARK and turn off the engine.
Re-connect the electrical connector onto the IAC. Start engine. Idle speed should be governed by the ECM at approximately 600-650 rpm in "DRIVE" (for unmodified cars). Idle speed in NEUTRAL or PARK is less significant, and will be higher.

http://216.121.161.76/files/TBTPI.jpg

Throttle Position Sensor (TPS) Tools needed:

1. Digital Volt-Ohm-Meter (VOM)
2. Breakout jumper wires or probes (make your own)
3. AutoXray, Diacom, or similar scanner will replace the VOM and jumper wires.

Turn on ignition, but don't start the engine.
With a diagnostic scanner: plug in the scanner and read the TPS voltage. It should be 0.54Volts +/- 0.07 VDC.
Connect the VOM to the TPS electrical connector terminals 'A' and 'B'.

With a breakout jumper: Disconnect the electrical connector from the TPS. Install the breakout in-line, between the TPS and wiring harness connector. Connect the meter probes to terminals 'A' and 'B' on the connector. ('B' is the positive connection, 'A' the signal ground, or negative.)
With probes: If you have very slender probes on your VOM, you can back-probe the TPS connector while it is attached to the TPS. If you have made probes of large dressmakers pins or a similar item, you can back-probe the connector as well. Connect the meter probes to terminals 'A' and 'B' on the connector.

Turn on the ignition to read the TPS output voltage at the idle position. The reading should be 0.54VDC +/- 0.07VDC. The ideal is the center of the range, 0.54VDC for a stock engine. To adjust the output voltage, loosen the two Torx screws holding the TPS to the throttle body, and slightly rotate the TPS up or down, reading the voltage until it comes into specification. Tighten screws. Using the throttle lever, rotate the throttle to WOT (wide open throttle). The TPS voltage should be over 4.0 volts. Close the throttle again, and then slowly open it to WOT, observing the voltage reading. It should increase progressively and in a linear fashion. If it sticks or jumps or falls off at all while doing this check, the TPS sensor may be failing and could be a cause of stumbling and driveability problems.
After achieving the desired setting, turn off the ignition switch. Remove all jumpers or the scanner and reconnect the TPS connector as required.

Reinitializing the ECM

If you set a DTC during the procedure, the SES light should be illuminated on the dash. This ECM retains DTC data for the previous 50 engine starts, so the codes will eventually be cleared. If you want more immediate results, after shutting down the engine disconnect the negative battery terminal for five minutes. This will clear the ECM of all diagnostic trouble codes. Clearing the ECM also clears any data learned about your engine, and clears the radio presets. If you have a Delco-Loc or Theft Loc II radio, make sure you follow the procedure to unlock the radio protection before disconnecting the battery. This five minutes is also just about long enough to clean both battery cables. Reconnect the battery. When you first start the engine after clearing the ECM, the engine will operate with base parameters programmed into the ECM PROM. These parameters may not be optimum for your engine, but the ECM will enter a Block Learn Mode soon after the engine is warm and enters Closed Loop Mode. The ECM will write new data tables specific to your engine and will eventually rely on those tables instead of the base tables of the factory program. You can expedite this process by driving the car for 20 minutes under varying conditions to allow the ECM to initialize. Or you can wait and drive the car normally at your convenience. The BLM tables are constantly being updated as sensor input ranges change, but the greatest change will occur within the first twenty minutes of Closed Loop operation. - Vader

2.8RS

iTrader: (5)

Yeah the car starts up fine. When it first starts up the RPMs go up to 3500 to 4000. It goes that high because when I adjusted the TPS I had to rotate the TPS all the way up then open up the throttle with the screw to get the TPS to the right voltage.

Bazookajoe254

When I start my car it does idle around 1000 but after driving when I come to a stop it still idles around 1600. I replaced the IAC valve today, and disconnected the negative terminal on the battery while doing so.

One thing I don't understand that was said earlier about twisting the TPS a little bit...if it has two screws, how can you twist it? Unless you mean take it off and twist the part that catches on the lever of the throttle plate?

Anyway, I'll try some more tomorrow...I'll have to ask people I know if they have a digital VOM, because ours just has a needle and the only thing I can do with that is generally see if it's between 0 and 1 lol

Street Lethal

iTrader: (16)

^ Yes, get yourself a digital VOM and make sure the sensor is adjusted corrrectly. After installing your new IAC, re-setting your TPS, and making sure that your throotle body is clean, and the linkage is not binding, if the idle is still too high, try re-setting your idle speed via the IAC (see above)....

The only other thing that can make the idle idle that high is a vacuum leak. If everything is installed, and set correctly, and the idle is still too high, check your PCV valve, EGR valve, and brake power booster for any vacuum leakage. These areas are strong enough to bring the idle up that high when the engine is fully warmed up....

2.8RS

iTrader: (5)

I thought vaccum leaks made your idle really low and rough.

Street Lethal

iTrader: (16)

^ Just the opposite. Also, it highly depends on where the leak is prevalent, in reference to how the car is behaving. When you press down on the throttle, your introducing more air into the engine, and RPM's increase. If you have your engine parameters set via the factory specifications, and you have a vacuum leak ([i]not[/u] a compression leak), it is supplementing additional air into the combustion chambers....

Vacuum leaks do not release air from the engine, it does just the opposite. Remember, an engine is a giant air pump, and if all cylinders are providing good compression (no compression leaks), then their going to pull air in from every possible location, including areas with vacuum leakage. When you hear the term "leak", don't misunderstand it's concept, nothing is coming out. If you put your hand over any vacuum leak, you'll feel air being sucked in, not out....

... and more air = more (higher) RPM.

2.8RS

iTrader: (5)

I've had problems before of low rough RPMS and people alwasys asked "vac leaks?"

firstfirebird

iTrader: (3)

A vac leak causes a lean condition, in turn raising idle. Running rich causes the RPM to decrease.

Street Lethal

iTrader: (16)

^ People might have asked you "vacuum leaks?", but this is usually the most common (and first) question when an engine has an ailment. Also, like I stated, it highly depends on where the vacuum leakage is, to understand why the engine is acting the way it does. Rough idle can be due to a faulty ignition system, including bad ignition module, coil, wires and plugs. It can also be due to poor fuel distribution, clogged injectors, filter and pump. Could also be a bad O2 sensor, which, based on the information it sends to the ECM, can cause a bad idle (if not reading correctly...

Rough idle = bad mixture, or poor spark. Combine that with additional air (from a vacuum leak), and you'll have yourself a poor idle, and possible stalling. Too many variables to pinpoint an exact cause, that's why people throw out the term "vacuum leak", as if this solves the problem immediately. The best way to determine if you have a vacuum leak (assuming all else is good) is if the engine "bogs" upon hard throttle, and/or the RPM's run too high at idle....

firstfirebird

iTrader: (3)

I agree with Street Lethal. Although the o2 sensor isn't read by the ECM untill the engine has reached operating temp, or has been running in excess of three minutes.

2.8RS

iTrader: (5)

This is all making snese to me now. I just tried to get the idle down to the 400 range like you stated above but was only able to get it down to about 1200 before it died. Could modifications have something to do with my problem .I have headers with a broken bolt that was broke before I got the car, gutted cat (previous owner), and a cat-back system.

Street Lethal

iTrader: (16)

^ Remember though, in open loop the engine will run slightly higher in RPM regardless (during warm-up), but when closed loop becomes enabled at around 92 degrees (it fully enables at around 165-170), then the ECM becomes solely dependent on the O2 sensor's data. If it's sending information that is suspect, then that bad data will cause a bad mixture, in turn causing a rough idle....

Bad O2 = Questionable idle mixture

2.8RS

iTrader: (5)

I was planning on replacing my plugs, wires, distributor cap, and the O2 sensors soon anyways. Also would I have to disconnect the EST as stated above to adjust the idle properly. I don't know where that is on my motor.

Street Lethal

iTrader: (16)

^ I rarely ever did when I had my L98 and LB9 engines. It is not mandatory, just a preference, so don't worry about disconnecting the EST. Just set your IAC correctly with Vader's procedure above, then move on to the next possible culprit....

2.8RS

iTrader: (5)

Right now its raining so...
I don't think that I have any major vaccum leaks because I have checked multiple times and it was in the shop a few months back to fix all the broken vac tubes. The problem is that the motor won't go blow 1200 RPM without dying. That RPM and lower the motor spits and sputters and then dies below 1200. 1200 is about the lowest the motor will go. Not to mention I have to open the throttle back up to get the TPS adjusted right.

Street Lethal

iTrader: (16)

It's difficult not being there to understand what you mean when you say that you have to "open" the throttle body to adjust the TPS sensor. This alone sounds like your problem more than anything else. Also, I would never trust any other mechanic's work. Everything needs to be given the once over when received from the shop, as far as I'm concerned...

Once the rain subsides, get out there and set your IAC correctly. double, and triple check for any possible vacuum leakage (spray some carb cleaner while the engine is idling in specific areas), if RPM's increase, you found your leak). If no leaks are detected, let's move on to that faulty TPS sensor, as it honestly sounds like the problem might be that. I just adjusted my TPS on the 3.1 for fun, and I don't what your referring to in reference to "opening" the throttle body to adjust the TPS...

2.8RS

iTrader: (5)

The srew on the drivers side of the TB is what I'm talking about. To get the TPS to the right voltage I have to adjust the screw so that the throttle opens more and the TPS gets up to the right voltage. I'll get some pictures up to show you what I mean.

I have sprayed carb cleaner on all the hoses I could find and all over the engine. No difference in the idle speed.

Street Lethal

iTrader: (16)

^ Okay, I'm starting to become convinced now that it's your TPS. Either you have a bad TPS sensor in itself, or your having problems setting it accordingly. Remove the TPS entirely, and set your fast idle screw (the screw that your adjusting) so that it meets the throttle stop...

Meaning, with the TPS sensor off, looses the fast idle screw so that it is not touching the throttle stop on the liokage, then re-tighten the fast idle screw so that it "meets" it, and no more than that...

With that said, re-connect the TPS sensor, and WITHOUT opening the throttle body (without turning the fast idle screw clockwise), set TPS voltage as as possible. Then set your IAC as directed above, then adjust your TPS sensor again to desired settings...

2.8RS

iTrader: (5)

The TPS is only a month old if that. When I rotate it I have to rotate it up as far as it will go. Even then the TPS doesn't get up to the minimum of .54V. Then I have to adjust the idle screw, hence the high idle, to get it up to .54V. I'll mess around with it and see what I can do.

Street Lethal

iTrader: (16)

Remember though, as you open the throttle blades to set your TPS, your increasing air consumption, in turn raising your idle. The fast idle screw is not to be touched from factory settings (hence the reason why they cap it from the factory). You need to bring that idle screw back to its original setting (as described), then re-set everything else accordingly. If the TPS won't comply, then you have a bad TPS, regardless if it's brand new. The throttle blades do not have to be open at idle (not even a crack), that's what the IAC (air valve) is for....

2.8RS

iTrader: (5)

The best I could do for the idle is about 1200 withour the motor dying. The IAC was unplugged and the TPS is too. I need the car running for tommorow so I'll have to mess with it later. Would my motor need to run at hight RPMs because of my headers and exhaust?

Street Lethal

iTrader: (16)

^ Not at all. The only thing that affects idle (in reference to raising it to avoid stalling) is cam overlap/Duration, and/or if the engine isn't running properly to begin with (with your situation definitely being the latter of the two)....

Street Lethal

iTrader: (16)

Also... the TPS needs to be connected when setting the IAC valve. Again, back out the fast idle screw to where it just meets the bracket stop, set your TPS as close to desired voltage as possible, then set your IAC with Vader's instructions posted above....

2.8RS

iTrader: (5)

I also tried to adjust the screw with the TPS hooked up. Now that I think about it the TB was closed all the way. It is just slightly open and the RPM is at about 1200 and a little rough. The TPS is set to the proper voltage.

From what you stated above with the cam duration, could I have problems that I don't know about and could surface in the future?

Street Lethal

iTrader: (16)

I cannot emphasize this enough, the fast idle screw is not to be touched when trying to alter the idle. The computer will be thrown into a loop. The ECM wants to control your idle... through data sent via the IAC/TPS.

The ECM needs to be reset. Disconnect the battery for five or so minutes, then plug it back in. With the fast idle screw positioned correctly (without the throtttle blades being open, remember, the IAC allows for it to idle), set your TPS as close as you can....

Once you get it as close as you can, then follow instructions to set your IAC. When finished, allow the BLM to relearn everything all over again. Remember, the fast idle screw is capped from the factory for a reason. Unless you do your own tuning with a laptop, it is not to be touched. The throttle blades are to be closed during idle, not open one bit (this is why your idling high, that is, if you really don't have a vacuum leak)...

Street Lethal

iTrader: (16)

Please tell me that your referring to future mods, and that your not currently running an aftermarket camshaft....

2.8RS

iTrader: (5)

As far as I know the engine is completly stock except for the whole exhaust. I didn't touch the TB screw to adjust the TPS. I put some tape around the lever on the TPS so that I could set it right. I have checked and the TPS voltage is correct up to WOT.

Street Lethal

iTrader: (16)

If you are sure that the TPS is functioning properly, and that the IAC was set correctly, and that there are no vacuum leaks prevalent.... it's just a matter of trial and error from here (because the fast idle screw was touched, doesn't matter when or where, the fact that is was touched is the problem).

Back your throttle screw out a little more, then set your TPS again, then the IAC. Reset ECM, then check your idle. Still too high, back out the idle screw again, adjust your TPS, IAC, reset ECM, and check idle. Too high? Back out your idle screw again, reset TPS, IAC and ECM, and check idle... and over and over.

Same principle as adjusting your carburetor, only, the ECM is the mediator...