Cleaned TB--WOW!!

[Tweeter400]

I cleaned the TB this weekend on my truck because my pedal was sticky. The whole TB in front of and behind the butterfly were pure black. Took me about 15 min to get most of it out. No problems with a sticky pedal though!! I change my air filter regularly, is this just normal?

 

Thanks for all the info!!

 

 

 

[dadejak]

How Many Miles??

 

What did you use to clean it. Carb Cleaner?

 

Thanks,

 

Jack

[Tweeter400]

It has 45K on it and I used STP air intake/throttle body cleaner. Mine was so bad I had to use a lint free cloth to get some of it out, not recommended but I had to.

 

[seadoons]

Can someone describe the throttle body and also describe how to clean it?

 

Thanks.

[JayMan]

The official Helm shop manual recommends cleaning the TB and the IAC passages every 50,000 miles. I think that's fine if all you do is Interstate driving in a moderate climate.

 

If you live in a very humid climate, and/or a very cold climate, and do a lot of very short trips where the motor never quite warms up, you had better do this once a year. Especially if temps can dip to -40 like around here.

 

The reason is modern Emissions Controls. The PCV (Positive Crankcase Ventilation) sucks a lot of the oily vapor in the engine back into the intake manifold. This is supposed to keep the valve covers clean and with the lower pressure in the crankcase, the rings seem to last longer too.

 

There is also the EGR (Exhaust Gas Recirculation) system, which puts a controlled amount of exhaust gas back into the intake manifold to improve emissions performance. Combine the oily vapor with exhaust gas and you develop a black carbon residue and/or a black sludge inside your intake manifold.

 

Note where the EGR puts the exhaust gas, almost directly behind the TB. That goes a long way to explainng the NORMAL carbon residue on your TB. If really excessive, the throttle blade can actually stick.

 

I really wouldn't use an off-the-shelf carb cleaner, as it's not compatible with the coating on the TB or with the plastic intake manifold. I use 3M Throttle Body Cleaner, which claims it's safe for sensors, wiring, plastic parts, and coated TB's. It's very high quality, so you don't need much. Good thing too, very $$$.

 

I clean my TB and IAC passages every fall. I ignored the IAC the first time around and had a rough idle by next spring. Had to take off the IAC stepper motor and carefully spray off the pintle valve. It was encrusted in a black sludge. That cured the rough idle, though I did have to do the Idle Learn Procedure afterwards.

 

You really, really have to be careful with the IAC stepper motor. If you don't feel you can deal with that, best to have a GM tech do it. Whatever you do, don't try to move the pintle valve, as that can damage it.

 

The best way to clean the TB and IAC passages is, with the motor OFF, have somebody you trust keep the gas pedal floored. Carefully spray the TB blade and TB housing, though try to go easy on the right side as that's where the TPS (Throttle Position Sensor) is. You do NOT want fluid getting into the TPS!

 

You should be able to see the IAC passages at the top of the TB. Carefully spray into those too, letting the fluid run back out. It will be quite black. There is debate on whether to actually spray into the plastic intake manifold. I don't. Yes, if deposits are excessive, you will need that lint-free cloth to wipe it up.

 

Some folks have also used the upgraded PCV valve to reduce the oil consumption and excessive oily deposits/sludge inside the TB/IAC. I might try the newer PCV valve next time I change it.

[Tucson_02Silverado]

NBS 99-01...that black caked on stuff is from the EGR valve (EXHAUST)

 

Like the cars before EFI there isn't a defined maintaninence schedule, except if problems around 50K for cleaning the intake manifold, in this case the Throttle body as well at around 30K-35K miles.

 

Like mentioned before 3M or (GM approved) Throttle body soak. The TB is coated so be careful to the urge to just gouge the crust off with a screwdriver or exacto knife (maybe carefully trim down the "big" hunks with the exacto knife).

 

If you're going to do this yourself, don't forget to buy the TB gasket so you can put it back together.

[bandera]

I have a 2000 Z-71 with 54,000 miles on it. At about 50K changed spark plugs. I also replaced the PCV valve. But I have recently noticed a rough idle while sitting at red lights. I am one of those "short trippers" driving only 11 miles round trip on the days I work. I cleaned the throttle body a while back with STP throttle body cleaner. This is the first I have heard about the IAC , stepper motor, and pintle valve. Can you explain the proceedure to clean these? What does the IAC do?

[JayMan]

Ok, here is the "what the heck is that" and "how does it work" thing:

 

The air duct is held onto the TB (Throttle Body) with a large hose clamp. Carefully loosen the hose clamp and remove the air duct. If this is the first time, you may find the duct VERY hard to remove. Gently wiggle the duct off, do NOT yank on the air duct.

 

To prevent future problems, I always smear silicone dielectric grease on the TB flange and the inside of the air duct. This lubricant is resistant to high temps, is safe for plastics/rubber (Is also GM approved for the door weatherstripping), and is only a one-time deal - it seems to last forever.

 

With the air duct off to one side, you'll see the TB and closed butterfly valve. To the left are the cables for the accelerator and cruise control. To the right, at the end of the shaft, is the TPS (Throttle Position Sensor) and an electrical connector.

 

The buttefly valve has a special coating to minimize deposit buildup. The coating is somewhat fragile, so do NOT use any tools to scrape it! The proper solvent will quickly remove even the nastiest deposits and not harm the the coated blade.

 

Above the TPS is a little round black thing with an electrical connector. That's the IAC (Idle Air Control) motor. You'll notice the TB valve is fully closed, so to regulate idle airspeed, you have to add some "bleed" air around the closed TB valve.

 

The IAC uses a plastic disk - the "pintle valve" - hooked up to a stepper motor. When fully extended, the plastic disk covers both openings in the IAC well, so the air bypass is fully closed. If fully stepped the other way, the plastic disk fully uncovers the IAC well, resulting in maximum air bypass around the closed TB valve.

 

GM refers to the process of "stepping" the stepper motor as the number of "counts." Remember that unlike a regular electric motor with an armature, a stepper motor has an armature broken into many different fields, so the shaft rotates a precise amount every time power is applied to the next field. Remember Dot Matrix printers? That DADADADADADADA noise they made? They used stepper motors.

 

The PCM (Powertrain Control Module) needs a bunch of sensors to determine the proper engine idle: gear selection (Park/Neutral or in gear), A/C operation, IAT (Intake Air Temp), ECT (Engine Coolant Temp), CKP (CranKshaft Position), CMP (CaMshaft Position), etc.

 

As noted in my previous post, the EGR (Exhaust Gas Recirculation) system purposely adds exhaust gas into the intake manifold. The TB also has coolant flowing through it to prevent icing in cold climates. The PCV (Positive Crankcase Vent) system is always sucking up oily vapors from the valvecovers and introducing them into the intake manifold.

 

So, in "ideal" dry climates with constant Interstate driving with the cruise set at 75 MPH, you could probably go every 50k before needing to clean the TB/IAC. The absolute worst is short trip, stop and go, especially in winter. The colder the temp, the worse it gets.

 

You will eventually experience deposit buildup that can cause idle problems, hard cold starting, rough idle, etc. The whole point of carefully servicing the TB/IAC is to get those deposits out. I do mine every fall and it runs like a champ.

 

I should note some cautions:

 

1. Never, EVER try to move the pintle valve on the IAC when you have the IAC removed. You can strip the teeth on the acutator arm that goes into the stepper motor and RUIN the IAC. $$$

 

2. Never, ever use regular carb cleaner to clean out your TB/IAC! Use an appropriate solvent that is labeled as "safe" for the TB and the sensors around the TB (The TPS especially). I use 3M Throttle Body Cleaner: it works very quickly, you don't need much, safe for plastics, safe for sensors, and it's safe for "coated" TB valves.

 

3. If you DO remove the IAC to clean a badly plugged IAC passage, you MUST do the "Idle Learn Procedure" or the truck will have bizarre idle characteristics once you have everything hooked up. The idle could be as fast as 2,000 RPM.

 

4. There are a lot of delicate parts involved here. If you're not sure, and especially if you don't have the Helm shop manual in front of you, take it to a professional!

[JayMan]

I have a 2000 Z-71 with 54,000 miles on it. At about 50K changed spark plugs. I also replaced the PCV valve. But I have recently noticed a rough idle while sitting at red lights. I am one of those "short trippers" driving only 11 miles round trip on the days I work. I cleaned the throttle body a while back with STP throttle body cleaner. This is the first I have heard about the IAC , stepper motor, and pintle valve. Can you explain the proceedure to clean these? What does the IAC do?

OK, few questions:

 

Q:Did you use the exact AC Delco replacement plugs? The PCM is calibrated on those. Afermarket plugs can cause problems. My local NAPA carries the exact AC Delco plugs that were 50% (That's right, one half) the cost at the dealer!

 

Q:Did you do the "Idle Learn Procedure" after the new plugs and TB/IAC cleaning procedure?

 

Q:Fuel filter ok?

 

Q:Possible deposits on the intake valves, fuel injectors, combustion chambers??

 

The Helm shop manual actually recommends "extended" high speed operation to burn deposits off the spark plugs. If just driven in stop-n-go, the plugs will quickly foul. Maybe put in a can or two of that STP "total system cleaner" and go for a nice 100-200 mile trip somewhere.

 

Can't go any further until the Q's above are answered.

[frdfandc]

Q:Did you use the exact AC Delco replacement plugs? The PCM is calibrated on those. Afermarket plugs can cause problems. My local NAPA carries the exact AC Delco plugs that were 50% (That's right, one half) the cost at the dealer!

 

Q:Did you do the "Idle Learn Procedure" after the new plugs and TB/IAC cleaning procedure?

Not to flame on you but I have never heard of the PCM being calibrated to spark plugs. I have ran anything from stock replacement to 2 heat range colder plugs without any problems or without having to "mess around" with the PCM. All depends on the application. Now I do believe in putting Delco's in a GM, Motorcraft/Autolite in a Ford, and Champions in a Mopar. The only other exception would be running Champion copper plugs in a un-naturally aspirated engine (it saves the pistons in case of a detonation problem, the plugs melt first).

 

 

As far as the Idle learn procedure, it should only have to be done when the battery is disconnected for either service or replacement, because it "resets" the PCM.

[OUMike]

I've never had any pedal sticking problems, but I don't think a good cleaning of the TB would hurt. Has anyone ever decided to just replace TB? How does a TB work exactly?? Are there injectors underneath it? How often should these injectors be changed? Fuel Economy is a big deal to me. I recently changed all plugs, wires, PCV valve, air filter several months back. I'm afraid after reading this that maybe dirty TB or maybe even intake could be the source of my poor emissions performance. Any ideas on cleaning intake manifolds?

[bandera]

To answer some of those questions-------Yes I used the exact AC Delco plugs. I have used the STP upper cleaner. Has a new fuel filter and clean K&N air filter. But I have never heard of the idle learn proceedure--how do you do that? If all that is is disconnecting the battery for a while, I just replaced the battery about two weeks ago (had the rough idle before the battery change). How do you remove the IAC and the pintle valve to clean them?

[dstktmusa]

Could you explain the ILP as I have disconnected my battery and the truck would not idle until I put a couple of miles on it.

[JayMan]

 

Q:Did you use the exact AC Delco replacement plugs? The PCM is calibrated on those. Afermarket plugs can cause problems. My local NAPA carries the exact AC Delco plugs that were 50% (That's right, one half) the cost at the dealer!

 

Q:Did you do the "Idle Learn Procedure" after the new plugs and TB/IAC cleaning procedure?

Not to flame on you but I have never heard of the PCM being calibrated to spark plugs. I have ran anything from stock replacement to 2 heat range colder plugs without any problems or without having to "mess around" with the PCM. All depends on the application. Now I do believe in putting Delco's in a GM, Motorcraft/Autolite in a Ford, and Champions in a Mopar. The only other exception would be running Champion copper plugs in a un-naturally aspirated engine (it saves the pistons in case of a detonation problem, the plugs melt first).

 

 

As far as the Idle learn procedure, it should only have to be done when the battery is disconnected for either service or replacement, because it "resets" the PCM.

Actually, the ignition system is far more sophisticated than you think. It's "up integrated" as it cannot run by itself anymore, it needs all the critical sensors operational and everything in good working order. My 1984 Ford 302 with Jacob's Ultra kit will run on anything, so I put in the cheapest plugs I can find.

 

I've got the Helm shop manual, Volume 3, page 6-2202 in front of me:

 

To meet OBDII requirements, and provide much improved performance, the CPC (Coil Per Cylinder) system is capable of detecting changes in resistance from "reference" values. This is also part of the Misfire Detection (Along with changes in measured angle on the Crankshaft Position Sensor - an angle change that is outside expected values that is not caused by rough roads also indicates a misfire event ).

 

Depending on the nature of the misfire, the MIL will either flash or stay on. A flashing MIL indicates a misfire in progress, whether you can feel it or not.

 

The PCM has a built-in map to determine what is the acceptable resistance range, along with Open, Short, no ground, etc. This map is calibrated using the OEM AC Delco platinum spark plugs.

 

If you happen to use a plug that confuses the PCM, at the very least you may not get proper misfire detection or the best performance. At the other extreme, you will experience DTC setting when there really isn't a problem. Depending on the nature of the DTC, the fuel injector for that particular cylinder will also be disabled, which will REALLY affect performance

 

The CPC system also uses the built-in map to determine how to saturate the coils. It's capable of ramp and fire dwell and has internal over dwell protection. See also Volume 2, page 6-658, 6-696 to 6-697, and 6-720 to 6-721

 

The Idle Learn Procedure does not "mess around" with the PCM. The Idle Learn Procedure helps to quickly establish a new base idle speed, and it also helps recalibrate the short-term and long-term fuel trim maps. It will take time for the PCM to recalibrate itself after new plugs, especially if the old ones were degraded.

 

Idle Learn does NOT harm the PCM or "confuse" the PCM. If you want maximum benefit from new plugs, or especially to help the PCM quickly learn how to run on that nasty winter-blend gasoline (Thank YOU Mr. EPA! ), the Idle Learn is good to do.

 

The Idle Learn takes 10 minutes of your time and the PCM quickly learns it's new base idle, short-term trims, and long-term trims. So you will get all the benefits of new plugs and a clean TB without having to drive around a lot.

[JayMan]

I've never had any pedal sticking problems, but I don't think a good cleaning of the TB would hurt. Has anyone ever decided to just replace TB? How does a TB work exactly?? Are there injectors underneath it? How often should these injectors be changed? Fuel Economy is a big deal to me. I recently changed all plugs, wires, PCV valve, air filter several months back. I'm afraid after reading this that maybe dirty TB or maybe even intake could be the source of my poor emissions performance. Any ideas on cleaning intake manifolds?

Hello Mike:

 

Good questions. The newer Vortec TB is a "dry" Throttle Body as the intake manifold has fuel injectors for each cylinder, usually called Port Fuel Injection. I think the '94 V6 started with port fuel, though it may still use TBI, but please verify this.

 

If you have TBI, there are 2 fuel injectors mounted above the TB. There will be an aircleaner above the intake manifold just like with a carb. So, just like a carb, fuel is sprayed down the TB into the intake manifold. If you have the intake air duct going into the front of the intake, you probably have port fuel.

 

With port fuel injection, the Throttle Body is used to regulate airflow into the engine. The harder you work the motor, the more pedal you need, which not only opens the throttle blade for more air, but also commands the PCM, through the Throttle Position Sensor, to add more fuel and change the spark timing.

 

On the new Vortec there are quite a few sensors involved: Intake Air Temp, Mass Air Flow meter, Coolant Temp, Manifold Pressure (Absolute), Throttle Position, Crankshaft Position, Camshaft Position, gear selector position, A/C on or off, etc etc.

 

Poor fuel economy can be caused by a number of things. It sounds like you got the basics out of the way: plugs, wires, fuel filter, etc.

 

Have you tried a Fuel Injector cleaning? Like a Motorvac or a 3M pressure can or a similar method? That not only cleans the injectors but also cleans the intake valves and combustion chambers, which can be the source of many performance issues in a motor that old.

 

Even a few cans of something like STP Total Fuel System Cleaner helps and is better than nothing. I like to put in a couple of cans of STP TFSC every 6 months before going on a trip.

 

Have you ever changed the O2 sensors? O2 sensors degrade over time and this can cause poor economy, bad emissions tests, and catalytic converter damage.

 

What condition is the motor in? If it's all worn out, your options are very limited!

 

I think replacing a TB would be a last step as they're really $$$. I would sooner clean it good. If the intake manifold is truly caked up with carbon and sludge because of the PCV and EGR systems, you would have to remove the intake to clean it properly. That could be a very involved and $$$ operation.

 

Try the Fuel Injector / intake valve cleaning first. Then maybe look at aftermarket replacement O2 sensors.