Failed Emissions Test

Alright so I got the car all back together and I thought that everything was fine, until I got it tested. And that's when everything fell apart. Apparently I still have a higher than normal idle. The guy said that the engine was idling at around 1900-2000 which is about 800 rpms faster than what the highest they can start the test at. So what can I do to lower the rpms so that I can pass the emissions test? Thanks to all who help.

High idle like that is likely to be a vacuum leak or an intake manifold leak. Too much air entering the intake. Use an unlit propane torch to snoop around the throttle body. If the rpms increase due to the propane gas, you've found your problem. Its safer than it sounds.

Could also be an issue with the TPS or the ICS. Your manual will detail methods for troubleshooting these components.

How did you happen to find out about the unlit propane torch? Just the thought of it doesn't sound safe. To have propane gas turned on and put around a place that could have spark.

...Its safer than it sounds...


Pretty standard procedure in the industry to find vacuum leaks. Do it.


-MechanicMatt

I had suggested before that if you couldn't find a vacuum leak that you should disconnect and plug the hose from the ISC to the TB. Have you done that yet, and did the idle go down to normal with the hose plugged?

Go back to your previous posts about this issue and look at the suggestions. Then report back with what you have have found.

I am betting vacuum leak or bad isc valve. I have used water in a mist spray bottle to find them. Mist one part of the tb at a time and if the idle goes down for a moment then you found your leak. The TB and intake gaskests can present a problem.

Also did you check the idle scew that goes into the TB. Turn it in slowly (count the number of turn) if it goes in all the way and idle does not go down to normal then you have a vacuum leak. Then turn it back out to where you started.

Do you have a picture that could be used as reference for the idle screw? I have not been able to locate it yet. Please help.

I will help you find it, but before you try to adjust you must unplug the isc hose from the valve to the TB with the car running plug it with your thumb. Does the idle go to normal? If it does then the valve is bad allowing air to pass into the intake when it shouldn't. Do this first and check for vacuum leaks before you play with the idle scew

The scew is horizontal to the ground. There is another idle scew that is verticle to the ground on the TB linkage. don't mess with this one!!


The screw is on the right side of the TB as you face the car. It is located below the yellow arrow in this picture. is is low on the TB but above the intake plenum. There should be a black cap with black tab. Pull on the tab and the cap will come of the screw located inside the TB. Use a philips screw driver and turn clockwise to reduce air into the intake thus reducing idle. If the scew goes all the way in and the idle is still high then air is getting into the compbustion camber thru a vacuum leak.

http://img.photobucket.com/albums/v489/RossT/Image059-2.jpg

Please make sure all hoses are connected and not cracked per the underhood diagram. And then use carb cleaner or mist of water to check for vacuum leaks. More than likely you have a vacuum leak. It is also possible that your throttle cable or linkage is binding and not going all the way back when foot is off the gas pedal. TPS may also be a problem, but I rather doubt it. Once you get the idle down you will want to re-time it.

If all else fails take it to mechanic and pay for an hour of labor to track down the source of the high idle.

I snapped a picture also.

http://i77.photobucket.com/albums/j64/isc20/IdleScrew-1.jpg

-MechanicMatt

Thanks for the pictures of where I can find the screw in the manual it's a little confusing to try and figure out. Do you also have a picture of the ISC hose from the valve to the throttle body?

Sometimes when I try to figure out the pictures and descriptions in the manual they make me crazy.:screwy:

Find the ISC motor valve between the backside of the TB and the fierwall. It looks like this:

http://img.photobucket.com/albums/v489/RossT/Image005.jpg

just under the blue arrow

http://img.photobucket.com/albums/v489/RossT/Image059-2-1.jpg

Notice that it has two tubes coming off it for two hoses. One hose goes to the air cleaner and one hose go to the TB. The engine creats vacuum and sucks air from the air cleaner thru the open valve and into the TB. When the valve is shut, no air should go thru. The valves go bad frequently on these cars allowing air to pass when it shouldn't.

Find the hose that goes from the vavle to TB. YOu can disconnect it at the TB or the valve and plug it with your finger.

Good Luck.

Ross: The ISC valves have to be PWM, which probably has to do with them being such a common problem. What do you think?

-MechanicMatt

What year is that ISC valve motor? I think that I may have a different setup from what you are describing. I have the ISC motor but it doesn't look at all like the picture that you have posted.

Here's what mine looks like.
http://i303.photobucket.com/albums/nn152/burnidaho/P5030426.jpg

Yep. That's your idle control motor. Ross was refering to the earlier version. You apparently have a later model. Speaking of which, what year is your vehicle?

Your TPS may be out of adjustment, as Sbiddle aptly mentioned earlier.

-MechanicMatt

I have a 94' 1.0L with around 173K. How do I go about adjusting the TPS so that it is in the correct position?

Hey guys, I've never seen that type of ISC on that early of a metro. Is it possible that Flash has the wrong one for his car? Or am I not entirely informed?

-MechanicMatt

I thought something was strange back when he was wanting a MAP sensor. I new he had an earlier model. The part number he gave us for the MAP was a 95 or newer. I have one that matched his and I know it came from a newer metro.

Flash, you need to post your vin number. Your parts MAP, Idle motor etc are for a 95 or newer.

The parts and pics that we have been posting are for a 89-94 and maybee some very early 95's

There were alot of changes sometime during the 95 model year. They went from a obd1 to obd2 and many of the emission stuff (like idle motor) changed

Flash, find your TPS sensor it is on the left side of the TB (as your facing the engine) and count the number of wires that go into it. There are a couple of ways to adjust these things but we need to confirm the number of wires.

Also, look at your oxygen sensor on the exhaust manifold. How many wires go to it? 1 or more than 1?

This may explain alot of the confusion when we have been trying to help him.

Flash, it also looks like you figured out how to post pics. You may want to snap several pics of your engine compartment and post them for us.

91caprice, I am unsure about the PWM thing. Curious though.

Flash, on more thing for you to do. After you post your vin# if it comes up as a 94, I want you to post your eninge number, you can find it here:

http://img.photobucket.com/albums/v489/RossT/nuber-1.jpg

clean the area and write down an post the numbers. There will be 10 digits, we really only need to know the 4th, it will be a letter. That 4th digit (letter) tells us what year the engine was made.

For the time being my dad and I got the idle under control. We turned the factory service screw all the way out so that the engine would idle at about 1000 rpms. This is the one with the black cap that you're not supposed to remove but we did, as we failed to find the idle speed screw. Which of course still has to be a little higher than normal. We do think that the timing may be one tooth off one way or another, but that will be a job here in the next couple of weeks.

Unfortunately at the moment I won't be able to put the Vin# in this post because I'm away from my car. I will put all the information that I may have left out when I get back to town, but for the moment this is the best that I can give you.

Thanks to all who have helped me in diagnosing my car problems.