Cause of excessive carbon on IAC?

[MichaelRS]

In late 2015 at 161,735 miles the idle air control valve on my 2002 Toyota Sienna was acting up. So I opted for the cleaning rather than replacement.

That lasted for 4 years 9 months or 44,617 miles before it started acting up again this May. So in May of 2020, at 208,226 miles, I had a cleaned again.

THIS time it only lasted 7 months and 4k miles. So today I just said screw it and replaced it with a new one.
But when I looked inside the port of the old one, on the side that bolts onto the air intake, there was a LOT of carbon buildup. And when I took the end of a screwdriver and flaked a piece off, though small, it was about as thick as a fingernail.

So my concern is that there might be something else going on with my engine that it's spewing (for lack of a better way to put it) that much carbon into the IAC over a short period of time and as a result the new one may not last all that long.
Any ideas?

 

[BlueOvalFitter]

Excessive blow-by? The engine is getting up in age. Maybe, check out your PCV system.

 

[ripcord]

I've cleaned GM IAC valves before and only gotten several months before they started sticking again, so now I just replace them.

 

[Falcon_LS]

Prior to an oil change, get a can of CRC GDI IVD cleaner and spray it into the throttle body with the engine running, varying engine rpm (follow the instructions on the can). While this is a product primarily intended for the GDI crowd, in my experience it does a perfectly decent job with port injected engines as well. You might also want to run a PEA based cleaner, like Redline or Chevron Techron.

 

[Dave9]

Check your dipstick. Are you burning oil at a higher rate than you used to? If so, there you go.

Otherwise, you might have had a buildup previously but with it not causing a problem, you didn't check so didn't realize it.

IAC, cleaning is one aspect of refurbishing it. The other is that it is a moving mechanical thing, so whether screw or just shaft and bushing, it needs relubricated, especially after using a solvent to clean it.

On my oldest vehicle with a linear shaft IAC design, I use a solvent to clean it out, then shake it out and let the solvent evaporate a bit, then I put a drop of very light oil on the shaft, at the junction with the bronze bushing, work it in and out a few cycles, then leave it sitting propped up so gravity causes the oil to run down into the bushing and seep into it.

This is not going to fix a bushing too far worn out, nor burning oil to cause rapid buildup, but if done before the bushing is too far worn out yet, can result in multiple times the IAC lifespan you'd have otherwise.

I'd also wonder if you have a PCV valve that isn't working well to keep vapors reduced.... just thought I'd throw that out there, ignorant of what is in your 2002 Sienna.

 

[MichaelRS]

Check your dipstick. Are you burning oil at a higher rate than you used to? If so, there you go.

I'd also wonder if you have a PCV valve that isn't working well to keep vapors reduced.... just thought I'd throw that out there, ignorant of what is in your 2002 Sienna.

Oil burn has been pretty consistent over the last few years. About 12 oz every 1000 miles. And I have an oil analysis done through Blackstone every 3rd oil change, so about once a year (if that woukd show anything).

Just had my oil changed with this IAC job as it was time.

I guess I could check it, but I hope my PCV valve is working, since I replaced that with an OEM part from Toyota just last February at 203K miles.
I think the one I replaced might have been the original as the grommet was quite petrified and I totally overlooked it when i gave tbe car it's general service back in 2012 when i first got it with 136k on it.

 

[cb_13]

The components COULD be teflon coated from the factory. Ford did that with throttle plates for a long time and potentially still. Their official stance was they were not to be cleaned and must be replaced. The general consensus amongst those who worked on them was they could be cleaned but IF the teflon coating was removed by cleaning they would need to be cleaned every 15-30k miles due to build up.

 

[Dave9]

^ True, you have to be careful and not use abrasives to clean the coated throttle bodies or clean them more often, but I've never heard of teflon coated IAC. That doesn't mean there aren't any!

 

[Greasymechtech]

Skip the UOA's and shorten the oil change interval. Use a better oil filter. Clean the injectors. Change the spark plugs. Change the air filter. Change the PCV valve. Verify all sensors working(replace old sensors(o2/temp)).... Make sure cooling system is working properly and getting up to temp... or simply change the thermostat, coolant, and radiator cap.
Trace all vacuum lines and make sure none leak. Trim or replace as needed.
You probably have a little too much blowby. With your oil consumption, I'd also use thicker and/or HM oils. If using HM oils, move from blends to full synthetic. If using 5w30, step up to 0w40 or 5w40, or higher HTHS 5w30. A couple of the thicker additives below might help with your normal oil grade you are using. Don't get hung up on 1 brand of oil...

If you stick with the current oil/filter, I would use a bottle of of STP synthetic gold bottle, Lubegard Biotech, BG MOA, or Hyperlube ZRA... for the 1st top offs. After that, top off with whatever oil you are using and shorten the interval. Pick one for the 1st top off of each oil interval an alternate among these, and don't use more than 1 for each interval.

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The 4.7 has room for an overized PH3600 or PH8A filter. Pick a quality bigger filter and keep the oil cleaner. Use the XG8A, PBL30001, PFL41515, or 51515XP filter, or midgrade filter if budget doesn't allow synth media. Midgrade would be the toughgard, napa gold, boss...

Not much you can do to a higher blowby tired engine. Maybe with a little engine additive cleaning and better sealing from different oil grades or additives, you can make the IAC cleaning interval extended.

I was not impressed with your TBN for a 5k interval in the UOA section, regardless of the generic blackstonecomments. So, hoping a synthetic oil will work a little better, or the additive will spike your cleaning and improve the TBN retention.

Cut old oil filters apart and inspect for deposits. The engine probably had some neglect from previous owners.

 

[MichaelRS]

Skip the UOA's and shorten the oil change interval. Use a better oil filter. Clean the injectors. Change the spark plugs. Change the air filter. Change the PCV valve. Verify all sensors working(replace old sensors(o2/temp)).... Make sure cooling system is working properly and getting up to temp... or simply change the thermostat, coolant, and radiator cap.
Trace all vacuum lines and make sure none leak. Trim or replace as needed.
You probably have a little too much blowby. With your oil consumption, I'd also use thicker and/or HM oils. If using HM oils, move from blends to full synthetic. If using 5w30, step up to 0w40 or 5w40, or higher HTHS 5w30. A couple of the thicker additives below might help with your normal oil grade you are using. Don't get hung up on 1 brand of oil...

If you stick with the current oil/filter, I would use a bottle of of STP synthetic gold bottle, Lubegard Biotech, BG MOA, or Hyperlube ZRA... for the 1st top offs. After that, top off with whatever oil you are using and shorten the interval. Pick one for the 1st top off of each oil interval an alternate among these, and don't use more than 1 for each interval.

710 Engine Oil Treatment Products | Engine Oil Additive | Rislone

Rislone's Award-Winning Engine Oil Treatment Increases Oil Pressure and Protects Against Engine Wear. Rislone, Helping Your Engine Performance since 1921.

rislone.com

STP® Synthetic Oil Treatment | STP®

STP® Synthetic Oil Treatment combats petrol and diesel engine wear, deposits and oil consumption.

www.stp.com

Hy-per Lube Engine Oil Supplement with Zinc Treatment | Rislone

Rislone's Award Winning Engine Compression Repair with Ring Seal Renews Worn Engines and Rebuilds Lost Power. Rislone's Been Protecting Engines since 1921.

www.hyperlube.com

Bio/Tech Engine Oil Protectant - Lubegard

www.lubegard.com

BG Advanced Formula MOA® | BG Products, Inc.

BG Advanced Formula MOA® is formulated with 100 percent synthetic chemistry to protect engine components and fortify all brands of ...

www.bgprod.com

The 4.7 has room for an overized PH3600 or PH8A filter. Pick a quality bigger filter and keep the oil cleaner. Use the XG8A, PBL30001, PFL41515, or 51515XP filter, or midgrade filter if budget doesn't allow synth media. Midgrade would be the toughgard, napa gold, boss...

Not much you can do to a higher blowby tired engine. Maybe with a little engine additive cleaning and better sealing from different oil grades or additives, you can make the IAC cleaning interval extended.

I was not impressed with your TBN for a 5k interval in the UOA section, regardless of the generic blackstonecomments. So, hoping a synthetic oil will work a little better, or the additive will spike your cleaning and improve the TBN retention.

Cut old oil filters apart and inspect for deposits. The engine probably had some neglect from previous owners.I had a major tune-up in February of 2020, which involved replacing the coil packs in addition to the spark plugs

I had a major tune-up in February of 2020, at 203k miles which involved replacing the coil packs as well as the spark plugs (the ones that came out look good for 65,000 miles on them) and the PCV valve. Of course that doesn't mean that the newer ones couldn't have gotten fouled since then. I can inspect the front ones myself, but getting to those back ones, particularly with that phlegm still on is a problematic, so that's going to be an expense to have my guy do that. But that's when I just have to wait since I just spent a tidy sum for that IAC and having it replaced ( at least it's a tidy sum for me).

Also in February, at 203,400, miles I had the radiator and thermostat replaced. I don't go on the super cheap for stuff like that. Got a Denso radiator and whatever the most premium , or close to it, thermostat they offer thur RockAuto. So ever since last February, according to my gauge, it's now running a hair cooler then before I started having heating problems. (Started to get hot but no overheating when I would use for the AC). The old radiator was probably clogged.

I've been using Castrol 10-30 High-Mileage since I got the car with 136,000 on it in 2012. This oil change I switched to Valvoline 10-30 maxlife but that was only because they were out of Castrol at Walmart. I have a further question about that below.

According to the service records, at least the ones can glean from Carfax, the original owner treated the car pretty good with transmission flushes and any other service that was recommended through the dealer when it was recommended in the mileage charts mileage service charts. Although he was up more near the 6 and 7k oil change intervals.

Since I have had the car I have been using the Castrol 10-30 high mileage and shooting for an oil change between 5 and 6000. Though since mid 2018 I've been shooting for under 5,000.
I've never gone cheap on the filters either. I forget what I used at the very beginning but since 2014 I used the Royal Purple filter use the Royal Purple filter, but because I heard good things about it on this forum and the price was a lot better I switched to the Fram Ultra synthetic in late 2019.
Replaced Napa Gold air filter last September and it has
So here's my question about moving to a higher grade of oil (currently Valvoline 10'30 maxlife blend) I understand that may be beneficial to the tolerance of worn moving parts, but isn't that harder on oil flow over all through the channels that were designed handle a lighter oil? Does that have any negative effect on the engine/oil pump having to move the heavier oil?
I appreciate your help and advice

 

[kschachn]

No. A 40-grade or even a 50-grade isn’t going to harm anything. Your oil “channels” won’t be affected.