I doubt it. The code will come back pretty quick.
If you clear the code with battery disconnect, you won't have enough miles on the cycle.
You could phone a local emission place to ask there expectations as emissions vary from state to state, country to country.

 

No, you need to fix the vacuum leak.

Use a piece of garden hose and idle the engine. Put one end of the hose to your best ear and search around the intake side with the other end. A hissing sound will indicate the location of the leak. There are other methods described and shown on Youtube.

Check the Air Intake hose for cracks. Take the hose off and bend it. Pay attention to the accordion section. If you see cracks replace the hose or clean the outside and wrap it with duct tape.
Replace all vacuum lines. There is cheap vacuum hose available from the reel 15 to 20 ft will do.
Check all T-connectors for cracks and replace them when in doubt.
Make sure all hoses are connected.

Rubber looses it's elasticity over time. That creates leaks at the connectors.

Your leak is so big you should find it easily.

 

Thx for the information. I follow the following link to check the vacuum leak.


I sprayed the car brake cleaner over the hoses, clamps, intake manifold, etc. However, I didn't find anywhere leaking. It could be possible that I missed some parts, but honestly when the car is at idle, it doesn't stumble. The engine sounds pretty normal, not much noise. The car only stumbles a bit when it is on the highway running at 40mph and I try to accelerate.

I went to a mechanic today. He said it could be the upstream O2 sensor's problem. When he learned that I just replaced the sensor recently, he cleared the code for me, asked to drive for 50 miles and see what happens.

Will test drive again tonight. Thx a lot for all the inputs.

 

I like EricTheCarGuy too. I found a vacuum leak on my wife's contour using the spray can.

The proper air fuel mixture is close to 14:1.
It can get upset in two ways: 1. too much air, usually cause by a vacuum leak and 2. too little fuel.
Too little fuel can be caused by a number of things: bad fuel pressure, bad data from sensors to the computer, sticky fuel injector, etc.
Your mechanic thinks the heated O2 sensor may be acting up.

There is a easy to follow procedure to capture a lot of items in this area:


Now I know he is talking about the P0420 code that you don't have, but the lacquer thinner (NOT PAINT THINNER) will clean the whole fuel delivery system, the HO2 sensors and the catalytic converter.


Please keep track of what you do to the car and how it responded to your action. Also I think you have to erase the codes and see if they come back. There are some codes that go away, but not all.

Also, if you have not done yet, clean the MAF sensor with dedicated MAF sensor cleaner, the throttle body with dedicated throttle body cleaner, and replace the air filter and the PCV.

 

I also like the hilarious Scottykilmer

Let me try the lacquer thinner to clean up everything first. I will try to clean the MAF sensor, the throttle body and replace the air filter later, since I haven't fully learned how to remove each part yet, nor are there any handy tool sets beside.

Thx a lot for the inputs! Will update after my test drive.

 

Hello I'm back. Sorry for the long delay. So many things happened since my last post.

I was doing test drive one day, stopped by a police officer, and got a traffic citation although I explained that I was doing a test drive. I was asked to go to court three months later. After that, I always felt stressful when doing a test drive.

Cleared the code P1170 and drove for 50 miles on the highway. The CEL went on again, and the code was still P1170. Went to a mechanic. He thought it was the bank 1 O2 sensor. Bought a new O2 sensor and had it replaced. Drove for 95 miles. The CEL didn't show up. Went to do the smog test. Test shows that "Catalyst, O2 sensor, Evaporative system, EGR system not ready".

Went to the mechanic again. Read the ECU code. There is no code, which partly justified replacing the O2 sensor. Then the mechanic thought the ECU may have some problem, since all system monitors were never ready. So I bought a used ECU online and had it replaced. I also had him replace four new spark plugs and the PCV. During the replacement of the spark plug, the ends of two spark plug cables and one spark plug boot were found to have some parts burnt. Had those replaced too.

Now drove 75 miles already, went to do the smog test again. The result is still discouraging. "Catalyst, O2 sensor, Evaporative system, EGR system not ready". Only Oxygen sensor heater is ready.

What I have replaced so far:
Battery, upstream O2 sensor, ECU, PCV, spark plugs, spark plug cables, spark plug boot, air filter.

Still don't know why the system is still not ready. Maybe not drive enough miles?

I haven't use the lacquer cleaner yet. Would it do any damage to the fuel system?

Thx again for all the information.

 

"I haven't use the lacquer cleaner yet. Would it do any damage to the fuel system?"

I wouldn't recommend it if it were harmful to your vehicle. I have done 3 vehicles without negative consequences. I would not do it very often (every 75K miles maybe).
I think I told you to check the vacuum line to the EGR boost sensor. Also watch this:

If the valve can't open or clese because the lines and ports are clogged it will never be ready.

 

Thx for the input.

The problem is: after I replaced the O2 sensor, the CEL is always off and there is no code from the ECU now.

In fact I had a mechanic clean the EGR valve for me about one year ago.
I will check the vacuum line to the EGR boost sensor tonight.

I also found a post showing the similar symptom as mine
OBD-II never comes up ready - HELP! - S-10 Forum

There it came out as a thermostat problem. Will also check that later.

 

Good research! If the thermostat doesn't completely close it will allow for too much cooling and prevent the monitors form kicking in. Another cause could be the ECT sensor in particular if there has been any leak stop in the cooling system. The leak stop could collect at the temperature sensor and act as an insulator. In fact an relative of mine lost an engine because of that. he didn't know it was overheating.

I hope it is one of those. They are often overlooked.