1990 jetta spits and sputters

[superman_192]

1990 jetta 1.8L with 250,000 miles will start right up but will idle rough when cold. The idle will even out if allowed to warm up. Also if started and drove soon after car will spit and sputter while driving down the road. Again after the engine warms up the car runs perfectly. This problem doesnt seem to happen when the weather is warmer out say like 40 degrees.

[denisond3]

Those are the symptoms you would have if the idle air control valve was not letting the engine run at a higher speed until it was warmed up. Your car has the 'bypass' type of idle air control, where the valve is located in a rubber tube that bypasses the throttle valve. The valve could be sticking (its computer controlled), or the rubber tube that it is located in could be starting to leak air, making the engine run leaner than it should. I supposed it could be other things, like a bad engine coolant temp sensor - but due to the rubber tube probably being original, and perhaps the idle air control valve being original, those are what I would suspect first. The rubber tube is not a standard piece of rubbing tubing, but is a molded item specially made for its purpose. You may have get a standard length of tubing in the right diameter and try to make it fit though.

I have a 90 Jetta that does the same thing as you describe your Jetta as doing. Its bypass hose has been closed off because it was starting to rip in the middle. But being in far south Texas (Mexico is only 8 miles south), running poorly in cold weather is seldom a problem.