Diy Info - Some Uncommon Maintenance Items

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Finally got some time to put together a little DIY guide for some quick things you can do under the hood. Some of the pics look a little blurry, sorry about that - camera went stupid on some of the pics, now rectified for future pics (i.e., camera in trash now). NOTE that my engine garnish is removed in all the pics. If you have your plastic engine cover on, you will need to pry off the two threaded clips in the rear and the two acorn nuts (10mm) in the front. Careful that you remove the rear clips with even pressure and a turning motion - or they will break on you (I've already broken both of mine - no big deal). All these repairs were done with the engine cold - no sense doing anything when the engine is hot, just let everything cool down - do it over a weekend, etc.

Stuff mentioned below will take less than 30-45 minutes to complete for an average DIY - a good chance that most of the time will probably be spent looking for tools. Other than replacing the sparkplugs (cap and rotor on some models, plug wires) - these usually provide the little extra bit of maintenance (usually missed by many) that especially helps idle quality, reduce chance for hesitation from low speeds. Some will not apply for all models - do not attempt if you are unsure or lack appropriate tools. If in doubt, take it to a reputable shop.

As with any work on the car, especially around electrical sensors. It is generally safer to disconnect the negative terminal of the battery. Use a rag or similar to protect the exposed end of the battery - to prevent accidental discharge with the hot side or inadvertent reattachment of the negative terminal. This will also "reset" the ECM, making the most use of your cleaning attempts. Allows the ECM to get used to the cleaned sensors more quickly. Make sure you take the proper precautions when disconnecting power - many aftermarket and OEM anti-theft systems will be affected, sometimes in a very undesireable way.

Some topics that are covered - many of which were mentioned fairly recently on the forum:

- Cleaning the Throttle body on car - minimum type of service that I would recommend on a throttle body. Better to take the throttle body off the engine to clean, but that is a little more involved that some would like to get + not really necessary if you routinely clean the throttle body. This shows the typical accumulation over a 30K mile period for my car.

- Cleaning the MAF/IAT sensor (Mass Air Flow meter and Intake Air Temperature sensor). This will apply to North American market Corolla model years from 2000+. Previous model year 8th gen Corollas (1998-1999) and the majority of the earlier generations are MAP based (Manifold Absolute Pressure), there is no sensor that can be cleaned. Again, this shows the typical accumulation over a 30K mile period for my car.

- A quick look at the PCV (Positive Crankcase Ventilation) and its location on the engine.

- Lastly, a look at the OCV filter on the VVT-i equipped engines. This would also apply to any Toyota corporate models that have VVT-i - including Camrys, Celicas, 2000+ Corollas, etc. A clogged filter here is the leading cause of excessive valvetrain noise on the 1ZZ-FE engine with VVT-i, but not the only cause. If you noticed a steady increase in noise, loss of power, VVT-i malfuction (P1656 OCV Circuit Malfunction, P1349 VVT System Malfunction) - a clogged filter may be the cause. I've seen some filters come out clean, some completely packed with particulates. You can also clean the OCV valve itself in a similar manner - but I will leave that to another DIY. The chance of damaging the valve is non-zero - I would rather see people clean the filter than try and wrestle with the OCV valve - talking a $5 part (filter) vs a $200 part (OCV valve). Which all could eventually lead to a VVT-i actuator failure, a $500+ part.


On car, quick, throttle body cleaning - what you will need:

- Phillips-head screwdriver (for hose clamp)

- Flat-head screwdriver (for stubborn electrical connections)

- Flashlight (optional) to address the level of deposits inside the throttle body

- Old toothbrush and clean rags (NOTE check that toothbrush bristles will not dissolve in solvent - don't want to add trouble.

- Appropriate solvent (make sure it says throttle body cleaning, sensor safe)


First quick overview of some common components. Most of you should know where these bits are - but some might like to see some pics.

Location of the screw on my 2002 - most should be in a similar place.

Look at the throttle plate and the mouth of the throttle body. That is what you will want to be cleaning here. Note where the carbon / varnish deposits are.


First, need to pull the airbox cover to gain access to the throttle body. Disconnect the electrical connectors on the airbox - the VSV connector for canister closed valve, the EVAP air hose (vacuum hose - can be really tough to remove, just becareful, don't want to snap off the plastic nipple here), the MAF meter connector (you can leave both sensors attached to the airbox lid for now). Loosen the hose clamp, on the throttle body, unlatch the two forward clips on the airbox cover - angle upwards, wiggle the hose loose from the throttle body, and pull the whole assembly out.

Now you should have a pretty good view of the throttle body. Cleaning can be handled a couple of ways. One is to spray the solvent into its cap - providing something that you can "dip" the toothbrush or rag into - then apply liberally in, on, and around the throttle plate. The toothbrush helps, because its length can help reach a good bit past the throttle plate.

The other is to liberally spray down everything inside the TB and start scrubbing away at the stubborn spots. Solvernt spray is pretty strong - should be able to clean off a good portion of light carbon and varnish there - but some of the cavities might have to be scrubbed out by the toothbrush. Can always combine the two methods - spray first to loosen and soften the deposits, scrub to dislodge stuck bits, repeat for stubborn spots.

Articulate the throttle plate by rotating the throttle control arm on the outside of the throttle body. Just turn the cam-like mechanism attached to the cable to open the TB. While it is open, spray and srube immediately behind the plate. Don't forget to work all the way around the circumference and the now exposed, backside of the plate. For models with DBW (Drive-By Wire) - 2005+ Corollas, DO NOT attempt to move the throttle plate with the ignition (throttle body) powered on or damage to the throttle body will occur.

Here is what the TB looks like aftera few minutes of scrubbing and spraying. Allow the solvent to either evaporate on its own or blot up the larger pools of left over solvent with the clean rag. Becareful not to introduce foreign matter into the induction system. Allow everything to air dry as much as possible, the reinstall ductwork. If you want, you can take the time to clean the MAF sensor - while that is air drying, the throttle body should be close enough to being dry. If there is excessive solvent left in the induction system - the car will just burn it off. Unless you emptied the contents of the entire can into the intake - the chance for hydrolock and engine damage is very remote.


MAF sensor cleaning - what you will need:

- Phillips-head screwdriver (for MAF sensor - two screws, don't lose them)

- Flat-head screwdriver (for stubborn electrical connections)

- Flashlight (optional) to address condition of wires

- Appropriate solvent (I used my throttle body cleaning solvent, brake cleaner works great too - as long as it is non-clorinated, the also make MAF sensor specific solvent)


Close ups of MAF sensor (sensing wire) and IAT sensor


There is no set cleaning interval for the MAF sensor - it is not even considered a serviceable part. But many have had good results with cleaning this sensor.

To remove the sensor - pull the electrical connector off (disconnecting power first is generally a good idea). Unscrew two gold phillis-head screws from the corners of the MAF sensor. May have to bend the cruise control stay to allow enough room to pull the sensor out. Looking downwards into the sensor - the sensing wire and heated wire should look "shiny" and clean. Do not be tempted to physically touch the wires (some use Q-tips to clean them) - I prefer to use the solvent spray only. If the wire won't come clean with pressure from the solvent, then replace the sensor, as it is too easy to damage the little wires in there. Worse case, you'd have an intermittent connection - which would mean headaches down the road. But if you are able to spray the wires clean - you just saved yourself about $70 aftermarket, about $100-$130 retail. The IAT sensor on the MAF body is pretty tough - should have a deep amber color to it when new - just make sure there is not debris or oils on its surface. Make sure you don't lose or damage the thin rubber o-ring at the base of the MAF sensor - otherwise, it could cause a leak in the airbox, pulling unfiltered air into the induction system. Allow to air dry and replace into airbox cover.


PCV cleaning - what you will need:

- Elbow grease, maybe pliers for stubborn hoses.

- a 22mm wrench or socket (tighten to 20 ft.lbs)

- Appropriate solvent (same stuff as cleaning the MAF sensor)


Close ups of PCV valve - location is on the driver's side of the car, rear part of the valve cover. Can't miss it.


Like the MAF sensor, there is no set cleaning interval for the PCV valve - again, not even considered a serviceable part, very inexpensive - easy to replace. But again, many have had good results with cleaning this part.

Locate the PCV in the valvecover. Grasp the wire hose clamp, squeeze the ends and slide down and out of the way. Carefully rock the rubber cable back and forth until it starts to turn - should slip off easily at that point. Take a 22mm socket or wrench and loosen it from the valvecover - might take quite a bit of force, if this has never been changed before - OEM really wrenches it on there tight.

Once removed from the valvecover, note is an excessive amount of oil is dripping from the valve end or drips out of the PCV hose running to the throttle body. A little bit here is normal, but if oil is pouring out of the hose or valve - could have several issues you need to address soon. If everything looks OK - give the PCV a good shake - it should "rattle", indicating that it is freely moving inside. The valve is basically a one way check valve - it allows gases from the valvecover to vent infront of the throttle body, to be burned off during normal operation (this is also why the throttle body can get pretty filthy). But air is not allow to pass from the intake towards the valvecover. This allows normal combustion blowby to be vented outside to prevent overpressurizing the crankcase. Too much pressure will cause oil leaks to form. Even if the valve "rattles" - I like to give it a good spray of solvent inside and out. You'll be amazed by how much oil and carbon deposits this can hold. Once clean, allow to air dry, and replace.


OCV filter cleaning - what you will need:

- Extra set of hands, may need to remove intake manifold and/or alternator to get more room to work with

- Piece of wire or hemostats (tweezers) to fish the filter out, if the filter doesn't come out with the bolt

- a 14mm wrench or socket (tighten to 21 ft.lbs)

- Rags or papertowels to sop up the oil that will drip out of the head.

- Appropriate solvent (I used throttle body cleaner - becareful, as the filter body is partly made of plastic)


Pics of the location of the OCV filter, dirty (but clean) filter, and cleaned filter and bolt. Note that the filter has prongs that slid into the top of the bolt. May or may mot come out of the head as a single piece - more likely, it will be separate and be a PITA to pull out.


Locate the filter bolt, and remove with a 14mm wrench or socket (socket might tight, unless you have a low-profile version). There is a thin metal gasket that might be stuck to the bolt - make sure you keep that, don't damage it if you didn't but a new one (most can be reused). Remove filter (very delicate - pretty small filter with a plastic body (metal screen). Clean it throughly with solvent of choice. Spray in rag or paper towel, if you have a parts washer or small parts cup, let is soak a bit and see if there are any "chunks" in there. Once clean, clean the bolt, gasket, mating surface on the cylinder head - reassemble the filter onto the bolthead - carefully insert it into the cylinder head. If the filter falls off - you run the risk of crushing the filter with the bolt. You can use a little dab of grease to hold the filter on - grease will dissolve in the oil quickly. Tighten up the bolt to the recommended torque rating, start car. Don't be alarmed if a CEL is set - as there might be a momentarily loss of oil pressure to the OCV valve (a little bit of oil drained out when you removed the filter - I lost a few ounces of oil). Reset the ECM - let the car relearn some settings - should notice if the noise is diminished or not. Since mine wasn't dirty - I didn't notice any noise change. Others have experienced a revalation in noise reduction - might be worthwhile for a few minutes of you time to see if you can knock out that ticking noise.

We just hit 99,000 on our 2001 default_tongue Thanks for the info

Excellent writeup Fishman.

That is sure to help many.

Jay in MA



Printed out and saved. These are the often forgotten items that even I forgot about (I did MAF sensor clean once though).

As always, a great help FISH!


One question re: OCV filter cleaning. Since some oil comes out, would it be easier to do it during an oil change when oil is drained to decrease the oil spill?

Is it worth to put a new filter in rather than cleaning?

Thanks again!

Fish,One question re: OCV filter cleaning. Since some oil comes out, would it be easier to do it during an oil change when oil is drained to decrease the oil spill?


Is it worth to put a new filter in rather than cleaning?

Thanks again!

Good point - probably wouldn't hurt to do it during an oil change - but I don't think it will decrease the amount that dribbles out that much - as most of the oil drained out will be from the sump. That said - probably a good idea to do so, since you don't want to be circulating dirty oil that may gum up the filter you just cleaned up.

As far as a new filter - probably can't hurt. I know the next time I check the OCV filter - I'l probably end up replacing the filter with a new washer. I haven't priced them out at the dealership - but I would be greatly surprised if it was more than $10-$20 for that little filter and gasket.

I guess I'll find out soon enough - planning on taking a peek at the Matrix this weekend (weather notwithstanding) - that engine has two of these OCVs - one for VVT function, the other for valve "lift" function.

Great post Fish! If I may pick your brain a little. I recently replaced the thermostat on my 04 Pontiac Vibe. which I'm sure you know is a rebadged Toyota Matrix. Anyhow the engine still seams to run hotter than usual, about half on the temp gauge. the cooling fan wont kick in, unless I turn the A/C on (relay I think) but the vacuum switching valve keeps clicking now. I pulled the negetive battery terminal when I removed the alternator to get at the thermostat, so is this the ECM doing something to the VSV or do I have another problem?

Any help would be appreciated.

fish, how often should we be pulling, checking, and cleaning the OCV? is a new o-ring needed each time?

^^^ O-ring should be OK for a few times at it - mine was barely distorted with over 150K miles on the Corolla. Frequency probably depends on the owner - probably a good idea to pull it and see how things look, atleast the OCV filter - the OCV valve is a little tougher to get to and some have cracked off the base by accident. Good DIY directions on - some have less than 60K miles and their filter wsa completely clogged, other have gone the same distance and their filters were clean. It be nice to see how UOAs, OCIs, and type of oil used had a direct correlation between a clean filter or not - but I don't think many have studied it that closely. Mostly, people don't even bother unless the VVTi/VVTLi is making an excessive amount of noise.

i think i'll pop mine out when i have the valve cover off to do the bolts, i have a sample kit from blackstone on the way so i can sample the oil thats in it now to see how its doing. they're a few k away from the oil change mileage, it looks like they were doing every 3 months and not 3k miles, so it was being done more often than 3k miles which means it was probably mostly around town driving and at low rpm, bodes well for the lift systems condition!

Thanks for the great write-up. I did everything on the list, and was surprised to find all the parts very clean on my '03 with 60,000. I didn't think it would make much difference, but my wife said it "felt a lot better" after the cleaning. You were right on with your time estimate. Everything was very easy to get to, even the OCV filter wasn't bad, I was able to get it out and back in without messing the the alternator. One thing I will say is you need a deep socket for the PCV on an '03, as there's no room for a wrench. I found the OCV filter especially interesting- I couldn't even find mention of it in my Haynes manual.

Thanks again.


Glad that this helped. As for not finding much, that just means that you took great care of your car! Yes, the OCV filter and MAF cleaning are generally not talked about in most manuals, as they consider those replacement only. But a large number of owners have seen that some simple cleaning of those items can have a remarkable affect on drivability.

hi fish, great DIY write-up mate default_wink

just one question. i've tried to find out how to clean the OCV valve for the vvt and i couldn't find any using the search function here...

i was wondering if its possible to take out the valve itself without having to remove the radiator pipe thats blocking it? i cleaned my vvt OCV filter but i want to clean the vvt ocv valve as well. i noticed that newcelica and a few other forums have a diy but that was shown with the block out of the engine bay (obviously much easier to remove it than if it was still in the engine bay with all the pipes connected).

any help is appreciated!



Thank you for your regular professional contributions which benefit many of us.


Thanks Guys!

As for removing the OCV valve itself, that would be pretty tough to remove without moving hoses out of the way and possibly removing the intake manifold/alternator to make more room. The key there is to pull the OCV valve assembly straight out of the cylinder head - as you probably ran across stories of others that have accidentally snapped off the working bits if they tried to remove the valve at some angle.

The valve is an "interference fit" assembly, meaning that sometimes it doesn't want to come out - you'll have to rotate the assembly and try again, do not want to Hulk it and yank the valve out - the more room you have to work with, the easier and less likely you'll end up damaging the valve. There is also an o-ring that you would have to replace as well - you could try reusing the original one, but that will likely leak - o-rings aren't as forgiving for reuse as flat, crush washers.

Normally, if the filter assembly is clean, I would not worry about the valve. If the filter was completely clogged - then you'll likely have to look at more than just the OCV assembly for cleaning.

LOL, finally, I got some time this PM and I tried to clean the OCV filter in my 03 Corolla with 74xxx miles. Unlike gshwell who succeeded in a similar car, I failed miserably. Due to downward slope of the 14mm bolt I could not fit a socket. I used a 14mm wrench from a side, but it would not bulge, even with some hammer action. Afraid to round the bolt, I aborted.

Nest step would be removal of alternator and I had no time for that.

I guess next time I could try some penetrating oil, but I bet the filter is clean as I'm anal about oil changes. 3,000-5,000 miles every 6 months. Last couple of oil changes, I used small amounts of Mystery Marvel oil additive at the end of OCI to clean rings a bit (I have a minimal oil consumption issue). I hope my daughter (who drives the car now) will be meticulous about it too.

BTW, Fishexpo, how is your new Matrix. I considered one and test drove too when buying my new car.

Thanks for the article.

I'm always looking for preventative maintenance that I can do on our 'rolla to keep it running forever.

I've already done the PCV but not the other stuff on the list.

Hi fish!

Hey awesome diy write up man..

Wish i would have seen it back in 2010 when i joined the forum. Thats when i did a good tune up to my 98 corolla at 245k miles. A good 30 somthing thousand miles after i bought it.

Anyway after coming back to the forum and seeing this i figured, at 291k miles (45k after the first tune up) it was time to do this again, this time with the help of fish's write up..

So here are a few pics of the "after"...

(i was so anxious to tackle this job once more that i forgot to take pictures of it "before")

+I started by doing a piston soak...

This one is when i removed the TB i finally got to take a good peek at the intake runners.

(i was surprised they were fairly clean). Considering i never touched them before..

These are of the front and back sides of the TB respectively..

And this one is from the now clean TB back in place. default_smile


(Fish i meant to give ur post a 5 star vote but my big fingers touched the 3 star accidentally instead.. and i just couldnt change it. It says u only vote once. default_sad ...)

No worries man, don't worry about the ratings - I'll see if I can get that fixed later, or I'll just leave it. Always room for improvement and future DIY guides for the forums.

Anywas, nice pics! Pretty clean intake and now TB. Good job on getting the car up to almost 300K miles.

I take it, from your references on the piston soaking and future piston/ring rebuild, that this is one of the 1ZZ-FE that are heavy oil burners? Are you able to catch a lot of oil in your filter/catch can setup that I see in the pics?

Yeah, if it wasn't for heavy oil consumption on some of the 8th gen (mine hasn't so far ~255K miles, knock on wood) or EVAP issues (this is what plagues my car, EVAP codes always right before I have to smog, like clockwork) - this would have been a superb generation.

No worries man, don't worry about the ratings - I'll see if I can get that fixed later, or I'll just leave it. Always room for improvement and future DIY guides for the forums.


Anywas, nice pics! Pretty clean intake and now TB. Good job on getting the car up to almost 300K miles.

I take it, from your references on the piston soaking and future piston/ring rebuild, that this is one of the 1ZZ-FE that are heavy oil burners? Are you able to catch a lot of oil in your filter/catch can setup that I see in the pics?

Yeah, if it wasn't for heavy oil consumption on some of the 8th gen (mine hasn't so far ~255K miles, knock on wood) or EVAP issues (this is what plagues my car, EVAP codes always right before I have to smog, like clockwork) - this would have been a superb generation.

** Thanks man. And yes it is one of those famous 1zz's default_smile

I quit the heavy diesel 15w-40 and now using only high mileage synthetic 5w-30. With a 200-300 mile flush every three or four oil changes.

Its still drinking about a 1/4 to quart and a half every 4-5k miles..

** Yeah the paper filter inside it does make a great job keeping the inside of my TB and Intake nice and clean. thou i usually have to replace one or two of these little filters every oil change.. Here is a pic of what it looks like when is time ti get rid of it.....


On this pic it actually shows the way the plastic walls begin to collapse on the paper filter when its really full of nasty stuff..

I know i really like this car but i know when we get to rebuild its engine im gonna like it even more... default_smile

i just wish it was a five speed then it would be perfect.

Excellent instructions! Thank you very much!

Could you please help me find the part number for theCamshaft Timing Oil Control Valve Filter for a 2001 Toyota Corolla LE and where I may be able to buy it online?

If not online which national auto store is likely to carry it?

Thank you.

Might not be able to find that at an autoparts store, might have to go directly to a dealership. Toyota part number is 15678-21010, shoould only set you back about $8 or so.

Here is a picture of one that I just Googled up, incase you haven't see it. Has the part number again, just in case.