96 V6 1MZ FE excess gas consumption/emissions

[V6Toyota_Cam]

Recently on my 96 1MZ FE, I've been getting terrible gas mileage. Also I've taken my car to an emissions test because it's been due for one lately. I've done the test a couple of times and it failed on both tests when the RPM was increased. In all tests, it passed only on the curb Idle portions of the test. Here are the results of the tests:

Test 1 (ASM2525 Test at 1682 RPM):
HC ppm = Limit 57 / Reading 180 = Fail
CO% = Limit 0.32 / Reading 0.42 = Fail
NO ppm = Limit 421/ Reading 370 = Pass
RPM = 1682 = Valid
Dilution = 14.9 = Valid

Test 1 (Curb Idle Test at 714 RPM):
HC ppm= Limit 200/ Reading 100 = Pass
CO% = Limit 1.00/ Reading 0.11 = Pass
NO ppm = N/A
RPM = 714 = Valid
Dilution = 14.6 = Valid


Test 2 (ASM2525 Test at 1213 RPM) [taken after tuneup and a few weeks later]:

HC ppm = Limit 57 / Reading 192 = Fail
CO% = Limit 0.32 / Reading 0.53 = Fail
NO ppm = Limit 421 / Reading 493 = Fail
RPM = 1213 = Valid
Dilution = 15.6 = Valid

Test 2 (Curb Idle Test at 825 RPM):

HC ppm = Limit 200 / Reading 147 = Pass
CO% = Limit 1.00 / Reading 0.22 = Pass
NO ppm = N/A
RPM = 825 = Valid
Dilution = 15.6 = Valid

So far I have new oil, spark plugs, PCV valve, Cat and no OBD II codes. I'm sure that this emissions problem is causing such high gas consumption, but I'm not sure what to do to fix this problem. Someone suggested to me to remove the EGR valve and to clean it because it may be full of carbon soot (just like my intake and throttle body was before I cleaned them.) EGR problems usually cause the NO ppm to go up over time as it has in these tests. But what about the HC and CO, they have also gone up over time. Can a dirty EGR valve also cause increasing HC, and CO values? I do believe that the EGR is clogged up and I will clean the EGR valve system, but I'd greatly appreciate it if someone can also give me advice on anything else that can cause these high emissions if it is not the EGR valve. Should I replace an O2 sensor too, or is it just a problem with a dirty EGR valve?

[projektvertx]

I would try cleaning the EGR valve and all EGR tubing with some throttle body cleaner. Maybe soak the components overnight in a bowl of seafoam?

Bump for some other solutions?

[fenixus]

honestly, i think catalytic converter is going on this car. EGR reduces only NOx portion of emissions, and cat converter reduces all 3 of them, besides when it dies it kills MPG and engine power.

http://www.camrystuff.com/manuals/Ge...on_Control.pdf
page 1 & 18 (it's for gen4 though)

here is a screen shot of emissions table of gen4 5S-FE:


here is a screen shot of emissions table of gen4 1MZ-FE:


it looks like it. there is a chance that replacing o2 sensors might help it, but chances aren't so good. any trouble codes ? CEL on ?

cannot find similar FSM for gen3 now, but gen4 is pretty much same in this regard i think.

[73sport]

OP implies they replaced the CAT up there. Perhaps an exhaust leak would do it an injustice too.

NOX is pretty low on these engiens as the chamber burns pretty clean. I vote this thing is grocery getter, running lots of short trips, has excesive carbon build up, and has aged O2's. Carbon buildup raises HC and NOX as the burn is basically incomplete. Compression test anyone??? << might tell you something!

I'm not a seafoam advocate, but this may be a case where it needs detoxed! However, I start with:

Inspect for vacum leaks, idle is too high. Look at IAC hoses and flex hose aft air box.
Exhautt leaks before cat
Fill w/ 91 oct fuel add Techron
Drive a tank out of it at freeway speeds

IF, IF OBDII data is avaible, post your fuel trims, O2 readings (mV) and anything else we can use to evaluate.

Was the Cat Converter replaced?

Edit: mine only gets 22 to 24mpg so What is BAD?

[j_koncz 98 cam 5sfe]

cleaning EGR wont do anything EGR only operate at specific times when the computer sees it relevent. not at idle and not at acceleration. it will do it at a cruising speed that it knows it wont bogg down the car and only at precise times when all the values it needs are right. Check the colling system a hot engine will run higher HC and CO. Often aftermarket CAT's are inferior to factory ones that cost upward of 500 dollars. just something to think about.
ensure that your upstream and downstream O2 sensors are giving accurate readings. buy a DVOM or MultiMeter and backprobe your sensors to ensure you getting the right readings. Also if the engine doesnt warm up fast enough emisions will be higher and the CAT wont be at optimum operating temp. so thermostat could be another factor. a Good lil test of your exhaust is to hold a piece of paper at the tail pipe for a min see if it becomes saturated with any fuel or oil. like the previous guy said check for vaccum leaks. perhaps inspect your spark plugs, they might show sum signs as to what might be happening.

[73sport]

^ You're right, i doubt its the EGR leaking as that would whack the idle out bad as far emisions are concerned. The high idle needs to be resolved tho! <air leaks>

Edit also: why did the cat die? That implies it had issues for a long time, not an overnight issue. If it defaulted to LTFT,s the CEL would be on, but that doesn't mean the O2 sensors are working well.

Fix air leaks
Run cleanser of choice
replace O2 sensors

[j_koncz 98 cam 5sfe]

get some propane or some acetalene and release it slowly near the intake working it around seals and hoses attempting to find a spot where air is leaking in cus when the engine swallows that gas you've let in idle will change and it will indicat what area the leak is in when you allow gas into that area.
good way to find intake leak

[SilverSoarer]

To pass emissions you can put a bottle of B-12 Chemtool (essentially tolulene and acetone mix) into your fuel tank.

Or just put a quart of acetone into the gas tank - that should get you a pass - and buy you time to chase down the problems.

[fenixus]

Originally Posted by SilverSoarer

To pass emissions you can put a bottle of B-12 Chemtool (essentially tolulene and acetone mix) into your fuel tank.

Or just put a quart of acetone into the gas tank - that should get you a pass - and buy you time to chase down the problems.

the only trouble with acetone is that it melts rubber and plastic, so it might be fatal for the filler neck, plastic gas tank and even rubber fuel lines ?
correct me if wrong, but this stuff might end up badly.

[V6Toyota_Cam]

Although I replaced my old cat converter with a new one (the old one was destroyed inside), I still get carbon soot inside the rear of the tailpipe when I put my finger inside it to check. The car has a good idle around 1000 RPM, but I can feel that it's not operating completely smoothly as if there might be slight misfiring. I don't have any CEL codes, and the engine temperature gauge is usually exactly in the normal middle range between Cold and Hot. I just don't understand why the car is passing when it is tested at idle, but failing on the driving part of the test when the RPM is slightly higher then at idle?

[fenixus]

Originally Posted by 73sport

OP implies they replaced the CAT up there. Perhaps an exhaust leak would do it an injustice too.

NOX is pretty low on these engiens as the chamber burns pretty clean. I vote this thing is grocery getter, running lots of short trips, has excesive carbon build up, and has aged O2's. Carbon buildup raises HC and NOX as the burn is basically incomplete. Compression test anyone??? << might tell you something!

I'm not a seafoam advocate, but this may be a case where it needs detoxed! However, I start with:

Inspect for vacum leaks, idle is too high. Look at IAC hoses and flex hose aft air box.
Exhautt leaks before cat
Fill w/ 91 oct fuel add Techron
Drive a tank out of it at freeway speeds

IF, IF OBDII data is avaible, post your fuel trims, O2 readings (mV) and anything else we can use to evaluate.

Was the Cat Converter replaced?

Edit: mine only gets 22 to 24mpg so What is BAD?

right, i missed the part that cat is new. it might be then some coincidence causing mostly HC and CO to get rocketed high (especially they got HIGHER after cat replacement and tune up!), like excessive carbon buildup/sludged engine, also it might be a coincident that EGR stopped working properly (passed NOx emission before tune up) and resulted in clogged EGR valve and lines (check modulator and VSV too) which bumped the NOx higher.
as posted above, EGR system do not run at idle, it actually opens for exhaust gas recirculation above 2,500rpm. however a stuck half-open EGR will make idle rough that is when computer no longer can control it.

seafoam treatment might help to decarbonize engine. it won't help EGR though, OP would need to take that system apart and clean everything manually.

checking for vacuum leaks is a must if idle differs up from 650+/-50 (normal for gen3). fixing vacuum leaks "might" also fix EGR system. not sure if emissions were tested (i'm talking about emissions results OP posted) with bumped up idle speed (1,200-1,600rpm) or that was a "normal" idle on this car. more facts needed.

It would be wise also to start checking on EVAP as this one is responsible for most reduction in the evaporated HC (considering that new cat is good, no leaks/restrictions and does its part right in this reducing emissions process).

i'm sorry to say that, but without new oxygen sensors you will never know if cat converter is operating properly and if engine properly adjusts the A/F ratio. the black soot in exhaust tip you are seeing might be from running too rich.
replacing all o2 sensors on a V6 is costly (depending on emissions version it might be up to $400 for parts only).

i would rather think of WHY cat converter went down in first place. i think it's been said that when o2 sensors do not do a good job in adjusting the A/F ratio and monitoring cat efficiency then cat is not operating right and might become clogged (e.g. from constantly running too rich) and eventually dies.

[V6Toyota_Cam]

For now I'll start off cleaning the EGR system and then I'll move onto changing the O2 sensor(s) if it doen't fix the problem. If I'm going to change an O2 sensor, can someone please tell me the locations of them? I know that there is one at the front/middle-bottom area of the engine, but are there any other ones elsewhere too? If so, which one is most likely to fail that can cause problems? Can an O2 sensor also fail without giving me the CEL light?

[fenixus]

this is for california (upstream A/F sensors instead of thimble type narrow band ones) emissions V6 engine:


hope it helps.

if you need OEM/Denso part numbers use www.toyodiy.com/parts

or

you can go with NTK/NGK oxygen sensors for your car:
http://www.ngksparkplugs.com/part_fi...uv/default.asp

you may also try Bosch sensors, however i hate everything that Bosch makes for Toyotas and wouldn't personally recommend it. i had terrible experience with their spark plug wires and water pump.

also instead of plug & play sensors (with electrical connectors) there are also cheaper versions of universal sensors made by both Denso or Bosch. you will have to splice the wires into your old electrical connectors, quite easy as well, and could save you money.

A/F sensors are like double or triple the price of regular narrow band thimble type o2 sensors.

the upstream o2 or a/f sensors play role in adjusting the fuel trims (by ECU) based on detected oxygen amount in exhaust gas. downstream oxygen sensors are there for catalytic converter efficiency monitoring.

your o2 sensors may be dirty and sluggish or working in a limited range, but if they fail completely (e.g. no votlage flowing) they throw a trouble code. there is also a code for engine running too lean or too rich, but problem is that it must be VERY significant (like +/- 38% total fuel trim) for ECU to see a problem and pop up the code.

good luck!

[V6Toyota_Cam]

Thanks. Okay just so I'm clear about what is going on, if it is an O2 sensor that is not operating fully or properly, then it will only control proper emissions until a certain point...that is in my case only within the idle range. Is that correct? Therefore at higher RPM's, emissions will go bad because the O2 sensor is faulty. I'm just not 100% sure why emissions would fail ONLY at higher RPM (ex: at driving speed) and NOT at idle, and I would appreciate if someone could please explain this a bit more in depth of why it is happening ONLY at higher elevated RPM?

I will post my emissions test results below once again for quick reference:

Test 1 (ASM2525 Test at 1682 RPM):
HC ppm = Limit 57 / Reading 180 = Fail
CO% = Limit 0.32 / Reading 0.42 = Fail
NO ppm = Limit 421/ Reading 370 = Pass
RPM = 1682 = Valid
Dilution = 14.9 = Valid

Test 1 (Curb Idle Test at 714 RPM):
HC ppm= Limit 200/ Reading 100 = Pass
CO% = Limit 1.00/ Reading 0.11 = Pass
NO ppm = N/A
RPM = 714 = Valid
Dilution = 14.6 = Valid


Test 2 (ASM2525 Test at 1213 RPM) [taken after tuneup and a few weeks later]:

HC ppm = Limit 57 / Reading 192 = Fail
CO% = Limit 0.32 / Reading 0.53 = Fail
NO ppm = Limit 421 / Reading 493 = Fail
RPM = 1213 = Valid
Dilution = 15.6 = Valid

Test 2 (Curb Idle Test at 825 RPM):

HC ppm = Limit 200 / Reading 147 = Pass
CO% = Limit 1.00 / Reading 0.22 = Pass
NO ppm = N/A
RPM = 825 = Valid
Dilution = 15.6 = Valid

[V6Toyota_Cam]

Also, IF an O2 sensor is causing emissions to fail ONLY at driving speed RPM, should I try cleaning it first because chances are if the exhaust pipe is already full of carbon soot, then the O2 sensor may also be covered too. I know that there are spray products that are specifically O2 sensor safe, and has anyone tried cleaning O2 sensors with better emissions results after cleaning?