Sensor Locations

[rtyson]

:D

I have a 98 ES300 with 128K miles on it. I currently do alot of highway driving

and would like to keep good maintenance on my vehicle. I currently do not

have A-N-Y problems with my ES:

Platinum plugs replace at 85K, timing/Acc belts and waterpump was replaced

at 101K and I regularly service the rear diff fluid/coolant/oil-of course/air filter, tire balance/rotation, brakes.

I'm going to look into having the Front&Rear struts replaced. But my question is

should I just go ahead and replace the O2 sensors and EGR valve? Where are these 3 O2 sensors located as well as the EGR valve?

Also the 98 ES300 just has a conventional strut system (No AVS)?

I have been totally satisfied with the reliability and performance of my vehicle, this lexus impresses me so far. I'm a Toyota man anyway, I also sport a 2000 TLC that I've owned for 2yrs, excellent vehicle so far.

Anyway thanks in advance

rtyson-in-Missouri

[SKperformance]

if you get no codes i would not replace anything unless it needs it.

Clean you MAF ,get a motor vac(since the throttle body probably needs to be cleaned anyway), run premium gas, synthetic oil flush the tranny and add an inline filter and it should last forever.

[Toysrme]

@ 100,000+ Miles, the o2 sensors & cat are normally out, or on their way out anyway.

Yes, if you have the money, I would replace the o2 sensors.

I would take the EGR valve & ISC/IAC off & clean them by hand, clean the entire upper intake also.

Good to know you're changing the diff fluid, most people leave it! I would suggest either draining the transmission pan every other oil change (that's 10,000 miles), or flushing it every other year.

Install a tranny cooler too. SK's right, if you want your engine & tranny oil to come out looking exactly like they went in, install an aux. filter.

[rtyson]

Thanks for the response, great info at this forum, I did do a search on this site and found the location of the EGR Valve, still looking for the O2 Sensors.

You mentioned cleaning the MassAirFlow sensor and getting a MotorVac.

At 82K miles I did have a 'BG Fuel System Induction Service', for give my ignorance but what is this service doing (flushing the fuel system ?????

rtyson-in-Missouri

[Toysrme]

rtyson - unless someone is taking the fuel injectors themselves off the engine, dissasembling them & rebeuilding them (or atleast taking them off & sticking them in a sonic cleaner); they're just dumping a cleaner in the gas tank.

The main o2 sensors are on the exhaust manifolds. There is one more after the cat, it isn't used in tuning as much as it's used to verrify all the emessions equipment is working.

^ MAF, lot of write ups on how they work, but just incase you don't know. The ECU sends a measured voltage to a wire that heats up inside the MAF. The more air that runs across the wire -> the cooler the wire becomes -> the less resistance in the wire -> the more voltage returns to the ECU.

Thus, the ECU knows the volume of airflow entering the engine (Because it knows the size of the pipe). Because the wire temperature is also known, the ECU can calculate the MASS of airflow entering the engine (via volume & temp of airflow).

They can slowly get dirty over time & need to be cleaned. Just be careful doing so as they can be fairly sensative to mis-handling & mounting orientation. SK would be better equiped on how to clean one, he's written it up before.

[cube00]

Are you replacing the O2 sensors yourself? If so, read on.

The two on the exhaust manifolds usually burn-out first as they are much hotter. I replaced those two only. An engine code can be read at a parts store and they will tell you which ones need replacing. May need to look at a manual to figure out the banks they mention. Oh, and it is a Camry manual. ;)

You also have two choices of sensor styles. An OEM just plugs in, but at twice the cost. I opted for the "cut your own" type. The connector and splicers are a fabulous design. Water-proof and almost fool-proof.

Do the front exhaust first. It's the one right out in the open, on the front manifold, near the bottom. Easy to do. Though, you'll need the special O2 3/8" drive socket you can buy at a parts store.

The rear one is a royal pain! Hidden way up on the rear of the engine by the firewall. Cannot get to it from the top. Need car up on ramps, and good luck reaching it. I guess I have short arms, and could barely get to it only by feel. Much sweating and cursing seems to help, but it can be done.

Anything I can fix myself, I do. And this was one. Good luck.

[Toysrme]

Ya it's a stretch from the bottom, but less in the way. I've taken my rear out from the top. The trick is moving things like hoses out of the way.

[camlex]

Simple question:

Why would you change the O2 sensors when there is no error code?

Thanks,

[Toysrme]

Because that doesn't mean the o2 sensors are bad.

They become even more innacurate as they age - towards the rich scale for safety, wasting fuel.

They also become lazy, slow to respond, and at times they won't respond at all.