If it does, you will lose power, mpg. And can cause damage to the engine. Basically, it is like plugging the tail pipe so nothing can come out. Not a good idea. Try this test. Drive it at night and let it warm up to normal operating temp. After you drive home, let the engine run an craw under the truck to see if the converter is cherry red hot. If it is, replace it.
Let me know if this helps or if you have other questions.
Joe
Thursday, April 8th, 2010 AT 9:57 PM