I've done my research on possible causes... I have NO CEL on. EGR, VSVs and plugs were replaced two years ago. Plugs look good still.


I used a scan tool and checked operating coolant temp as well. It has been running a little cooler than normal the last two years after the above mentioned repairs, but when I'm at the inspection station the temp is plenty hot and even higher than normal after sitting in line for about 30 mins, so that shouldn't throw the reading.


I did notice the idle jumping back-and-forth between 740-780 RPMs. It was reading like a heartbeat on a monitor. It seems there may be just enough of a misfire going on to throw emission readings without throwing the CEL. Under any load the RPM reading is a smooth line left-to-right.


What do you think (PT/Toyo)? Coil going weak/bad? Faulty cylinder ignition wire?

 

High or low air/fuel ratios cause high HC. What was the number?

The IAC valve controls engine idle, have you cleaned the valve?

Any vacuum leaks? This can affect both idle and emissions.

Spark should gap 1/2 inch of air be white.

 

The scantool used didn't support my model year, only went back as far as 96. My Camry was made August 94 so it just made it into the OBDII era. We used the 96 setting since it was the same engine. However, it didn't report back any air/fuel mixture numbers.


Before failing the last inspection and using the scantool, I found a vacuum hose disconnected from one of the VSVs. I connected and ran right to inspection and failed again. After more research, I have found that the ECM might need to be reset after fixing the vacuum leak to reset anything the ECM was originally adjusting the a/f mixture for. I have reset it, but will need to drive the usual 100 or so miles before I can reinspect.


I haven't checked the IAC valve yet. It wouldn't hurt to clean it obviously, but I don't think it is a problem as the engine starts and runs fine.

 

Exactly why was the test failed? High emissions, lack of completing all test cycles or ?

If emissions, what were ALL the emissions numbers.

Did the idle issue go away after connecting the vacuum hose?

 

Reset will definitely help but like toyomoho has said, what part of the inspection is the car failing?

 

"94 V6 failing inspection for high HC @ idle"

"Before failing the last inspection and using the scantool, I found a vacuum hose disconnected"


Initial inspection emission readings:


ENGINE @ IDLE:


GAS - READING - LIMIT
HC ppm - 354 - 220
CO% - 0.42 - 1.20
CO2% - 13.9 - N/A
O2% - 1.0 - N/A


ENGINE @ HIGH IDLE:

GAS - READING - LIMIT
HC ppm - 83 - 220
CO% - 0.55 - 1.20
CO2% - 14.2 - N/A
O2% - 0.6 - N/A

 

Does coolant temp gauge needle position move when car is sitting or moving? If so, investigate coolant system. Needle should stay in one place all the time, which is typically just below mid-mark.

With the hose reattached, is the idle now OK or still varying? If not, find the cause of this problem.

Given the car is older then 1996, the emissions check may be for tail pipe emissions. No checking of computer itself.

Computer self checks are not going to affect how the computer adjusts A/F ratios. If a problem is fixed, the computer should within a few minutes (or seconds) readjust things, the self testing checks may take longer. As such, computer self checks on this year of car are not going to cause the car to fail the emissions test. The engine has a problem causing the A/F ratio to be higher or lower then normal.

Suggest you closely look at ALL vacuum hoses for damage that can cause air leaks.

Have you checked spark yet and the other items listed previously?

Try cleaning the throttle body and IAC valve. The internet has many posts on this.

Some suggest cleaning out the engine with Sea Foam. They spray it into the vacuum hose of the power brake hose going to the power brake canister.

Check any item that can cause the fuel/air mixture to be higher or lower which is not limited to air or fuel flow.

What model number V-6?

 

1MZ-FE V6 engine


The coolant temp gauge is reading lower than it always did. Needle is just above the C mark even at highway speed. It does rise if I have it running a few minutes at 2500-3000RPM while parked. I know a failing temp gauge can adjust the A/F ratio to affect the emissions, but I don't think it would explain the idle misfire.


Emissions are tailpipe readings, but they do put some kind of "box" on outside of car above firewall in front of driver's-side windshield while reading the tailpipe. Probably reading something out of the ECM the way a voltage toner reads electrical wiring?


All plugs and hoses look good. The minor idle misfiring was after hoses were checked. How "safe" or trusted is the Sea Foam procedure. Is it like Drano for the vacuum system?


Thanks for your time!

 

In what US state was the emission test conducted? From this may be able to find out what tests are conducted based on year of car.

The emissions box may reading engine RPM based on alternator signals. Did the test station have a display showing engine RPM? Some test methods plug into the cigarette lighter to obtain this info. To read the ECM requires plugging into the same port you use to check codes.

Misfire doesn't mean the engine is knocking along. Is the engine missing?

Make sure the coolant fans turn on with A/C and if engine idles too long.

Change out thermostat. When the coolant system is open for the change, flush out the coolant system with clean water from garden hose.

As you state coolant temp will change ECM operation and A/F ratios. The colder the coolant temp, the more fuel is injected and the higher the HC reading. The IAC valve also reacts to coolant temp as there are small coolant lines running to it.

The gauge needle should hold stead once engine warmed up regardless of driving conditions.

Sea Foam has been around for years. It's just a combination of common solvents you may have heard of plus a common mineral oil used as the carrier.

You can also buy intake manifold/throttle body cleaner in a spray can. Take off the large air hose to the throttle body and inspect inside the body. If lined with black grime, spray with cleaner and use a tooth brush and towels to clean it up. Once done, start engine and spray cleaner into throttle body to clean out more (follow any directions on the can).

If the engine idle is still varying, with engine running spray into the rectangle port on the bottom of the throttle body which is the air intake for the IAC valve. This will clean the valve which controls idle RPM.

Any cleaner such as Sea Foam or intake cleaner will cause the engine to bog down when used, you will need to increase RPM to keep engine from quitting.

When the chemicals a lot of smoke will come out the exhaust. This may be the engine cleaning or just the chemicals in these products coming out the exhaust as dark smoke.

The internet has many posts on clearing IAC valve with spray cleaner and using Sea Foam into the brake booster vacuum line. Do a search on the engine model and cleaning with these chemicals.

 

Sounding more and more like a "typical" repair for the Camry... lots of time, money, tearing apart and rebuilding.


There is no sign of a misfire or knocking at idle. No surging, no erratic idle, tachometer looks steady. Only noticed it when hooked up to a Scan Tool.

It's a NJ inspection at a state facility, not a private garage. Not sure exactly how their little "box" reads what it needs from the ECM. Drivers are not allowed to specifically see what they're doing because they make you exit vehicle and go front of garage lane (about 100' away) and wait for them. All I know is there is no direct connection to my car other than a tailpipe probe. No cigarette lighter or ECM port connection. The hood is never opened either. Somehow they are able to read if a CEL is on. (In the past, I would usually place a picture over the light along with my ABS light and it would go through no problem. Now it's an automatic failure if CEL on. It would read out with a "CEL ON" in the report they give you, even if my picture wasn't moved as if they moved it and physically looked at dash to check for CEL.)

Anyway, I'll check into those items ASAP. My AC doesn't work because of a broken line so I won't be able to test coolant temp and fan operations totally.


Thanks for the info, Mr. P.