Toyota Corolla Emissions porblem – recurring

[potat]

Hi,

I have a toyota corolla, 95, 1.8 L engine. I have been having emissions problem.
(To make it clear, it has failed atleast 7 times during the last 10 years).
My CO and HC are high (~1.6 2.1 % and ~160 -240 ppm) respectively. I have my mechanic
take care of the issue. Once he replaced the MAP sensor, and rest of the times, what he does
is, he increases the idle to ~1600 rpm and then the vehicle passes the emission, and then
set it to ~700 rpm (I think this is the factory recommended idle rpm). It is okay as I can live with it,
but was wondering whether there is an indication of something else that is causing the problem?

In the past several years, the vehicle has some of its emissions components changed:
O2 sensor, MAP sensor, EGR valve, among the many.

I appreciate your valuable comments or things that I could try to help this problem
on a permanent basis.

Thank you very much.

Topic

[college man]

for high Hc is usually from incomplete combustion. give the car a tune up plugs,wires,cap,rotor and ignition coil

high Co is a fuel mixture problem vacuum leaks will cause this condition(cracked broken vacuum lines,gaskets,boots) also clogged injectors
or restricted fuel filter and or pump. I would suggest a tune up with the parts listed above. I would also clean the fuel injectors as Erics video shows
and clean out the throttle body or carberator with throttle body or carb spray to melt the built up carbon keep us posted. C8-)

http://www.youtube.com/watch?v=41yFXjib … plpp_video throttle clean

http://www.youtube.com/watch?v=9CPqbaSg … plpp_video vacuum leaks

http://www.youtube.com/watch?v=bAOmUjAj … plpp_video power balance test

http://www.youtube.com/watch?v=fizKtru7 … plpp_video move a vehicle

[Josh3448]

Yes Im with College Man on this, these are also the steps that I would take to start addressing this concern.

[Matt]

Any check engine light on?

[EricTheCarGuy]

Quoted From college man:

for high Hc is usually from incomplete combustion. give the car a tune up plugs,wires,cap,rotor and ignition coil

high Co is a fuel mixture problem vacuum leaks will cause this condition(cracked broken vacuum lines,gaskets,boots) also clogged injectors
or restricted fuel filter and or pump. I would suggest a tune up with the parts listed above. I would also clean the fuel injectors as Erics video shows
and clean out the throttle body or carberator with throttle body or carb spray to melt the built up carbon keep us posted. C8-)

http://www.youtube.com/watch?v=41yFXjib … plpp_video throttle clean

http://www.youtube.com/watch?v=9CPqbaSg … plpp_video vacuum leaks

http://www.youtube.com/watch?v=bAOmUjAj … plpp_video power balance test

http://www.youtube.com/watch?v=fizKtru7 … plpp_video move a vehicle

+1

Those older systems are a bit ‘slow’ but as stated high HC and CO would indicate unburned fuel and incomplete combustion, also if your engine burns oil these numbers will also go up so if you notice a lot of blue smoke when you accelerate this found indicate that your engine is worn out and possibly loosing compression and burning oil.

[potat]

Thank you all for your valuable comments.

My spark plugs, wires, rotor caps and oxygen sensor were replaced about 3 years ago.
I understand the ‘changed parts’ do not mean anything as these components can go
bad any time. MAP sensor was changed ~4 years ago.

No check engine light or codes.

My engine burns little oil as I have to top the engine oil atleast once with 1/2 quart between
the oil changes (3000 miles).

As per my mechanic, the vehicle is smooth and he has not detected any leaks. (On another
note, my mechanic’s gas analyzer is down. His SUN MGA 1400 gas analyzer internal tubing
has gone bad, still waiting for the vacuum tubing diagram for it).

My car just failed the emissions test – 160 ppm HC and 2.0% CO. This was with a 1400-1450 idle
speed that was set by my mechanic.

Let me try to follow the steps as per your listing. For the fuel injector cleaning, I will ask my
mechanic.

I will keep you posted. Thanks a lot. In the meantime if anyone has any additional comments,
please post. Thanks and have a great week!

[EricTheCarGuy]

That idle speed is pretty high, twice what it should be in fact, and may be masking another problem or even causing the emissions failure, with an idle that high the throttle is piratically part way open which would throw off the idle numbers because it would read as part throttle numbers and not idle numbers. It’s probably not a bad idea to check for vacuum leaks as well as a lean condition can actually cause elevated HC and CO.

[potat]

Thanks, Eric.

Yes Eric, you are correct. The recommended idle for Corolla 95 (automatic) is 700-750 rpm.
My mechanic has set the idle speed to 1400 rpm (he has done this in the past to get
through the emissions test), and according to him ~1400 rpm would give a lean mixture
(I have a hard time understanding this, so I took his word).

I will check again for vacuum leaks and see whether I find any indications.

Thanks for many wonderful videos on youtube. When I first started getting my
hands ‘Dirty’, (2004) there were not many videos on car repairs.

By the way, do you know someone who owns a SUN MGA 1400 modular analyzer
(now the company is taken over by SNAPON)? I am trying to get the vacuum tubing
diagram for the analyzer so that it is easy to check the emissions at my mechanic’s
place. (I got a manual for MEA 1400, but that’s not the one I am looking for).

Thanks!

[EricTheCarGuy]

Band aids are not fixes and when it comes to passing emissions you need to fix not patch because it’s not just the emissions that you are addressing but also your fuel mileage and these days I’m sure that is a concern in addition to passing the test. BTW I used to perform emissions testing in PA and if a car came in with a high idle like yours it was an automatic fail.

I’m afraid that I don’t know anyone that owns that machine however you may be able to find replacement parts through Snap-on or perhaps on ebay.

[potat]

Thanks, Eric.

I agree with you. I need to get this problem taken care of.
Will update as soon as I am making any progress.

Thanks!

[potat]

Hi All,
A quick update, I got the SUN MGA 1400 tubing diagram and the analyzer is working fine.

Hooked up my car to the analyzer and looked at the exhaust numbers, it was a little rich and my
mechanic checked most of the things, and it seemed to be okay. Now he plans to test the emission
components one by one and see where the problem is. Will keep you posted. We had a spare MAP
sensor, and looks like MAP is not the problem. Thermostat is also working fine. I have pulled parts
from an old car the last weekend, hopefully that helps us to trouble shoot the problem.

Thank you!

[college man]

Quoted From college man:

for high Hc is usually from incomplete combustion. give the car a tune up plugs,wires,cap,rotor and ignition coil

high Co is a fuel mixture problem vacuum leaks will cause this condition(cracked broken vacuum lines,gaskets,boots) also clogged injectors
or restricted fuel filter and or pump. I would suggest a tune up with the parts listed above. I would also clean the fuel injectors as Erics video shows
and clean out the throttle body or carberator with throttle body or carb spray to melt the built up carbon keep us posted. C8-)

http://www.youtube.com/watch?v=41yFXjib … plpp_video throttle clean

http://www.youtube.com/watch?v=9CPqbaSg … plpp_video vacuum leaks

http://www.youtube.com/watch?v=bAOmUjAj … plpp_video power balance test

http://www.youtube.com/watch?v=fizKtru7 … plpp_video move a vehicle

have you tried any of the above to see if your emission readings come down?

[dreamer2355]

Is your vehicle OBD2? Id be looking at fuel trim numbers too if it is.

[EricTheCarGuy]

Quoted From dreamer2355:

Is your vehicle OBD2? Id be looking at fuel trim numbers too if it is.

95 is pre OBDII which started in 96.

On those older vehicles once you have your tune up stuff taken care of and you’re sure you don’t have any vacuum leaks the next step I would often take if the vehicle still failed was to replace the O2 sensor, I know you say you replaced yours but back then it was almost like a maintenance item every 60K. The MAP sensor is a dead end as that would not cause increased emissions without some form of performance problem to go with it. The coolant temp sensor IS a possibility but you would need to check it’s resistance against the temperature chart found in the service manual to verify it’s operation, it’s not difficult you just need to know what readings you should get for a given temperature.

[dreamer2355]

Quoted From EricTheCarGuy:

95 is pre OBDII which started in 96.

On those older vehicles once you have your tune up stuff taken care of and you’re sure you don’t have any vacuum leaks the next step I would often take if the vehicle still failed was to replace the O2 sensor, I know you say you replaced yours but back then it was almost like a maintenance item every 60K. The MAP sensor is a dead end as that would not cause increased emissions without some form of performance problem to go with it. The coolant temp sensor IS a possibility but you would need to check it’s resistance against the temperature chart found in the service manual to verify it’s operation, it’s not difficult you just need to know what readings you should get for a given temperature.

Some manufacturers did start using OBD2 in 95 seeing as that was the cross over year, so i wasnt sure if he had a OBD 2 DLC port or not L:D

[EricTheCarGuy]

Quoted From dreamer2355:

Some manufacturers did start using OBD2 in 95 seeing as that was the cross over year, so i wasnt sure if he had a OBD 2 DLC port or not L:D

The only one that I’m aware of that MIGHT have done that was GM since it was their connector in the first place, as for Toyota they didn’t see OBDII till 96.

[Author]

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