702_MJ Posted October 31, 2010 Share Posted October 31, 2010 Ok so here's the story, changed the thermostat back to stock because I just did a motor swap and the new motor didnt have a thermostat only one I had was a 160*. Checked the plugs and changed the oil. Then the alternator wasnt charging, and for some reason now it is, frickn weird. But now theres a rough idle...and yesterday when I was trying to test the alternator it didnt have this rough idle. So double checked the plugs again, checked the 02 sensor, was kinda black but figure thats from the 160* tstat running the motor rich. don't get any check engine lights or anything, so I figure its a vacuum leak, but all the vacuum lines I check are fine. What am I missing? Any suggestions? Thanks This is a 97' 4.0L btw. Quote Link to comment Share on other sites More sharing options...
Ron Posted December 1, 2010 Share Posted December 1, 2010 next i would check egr valve. remove and check for carbon build up and or sticking valve. then with a omemeter check throttle posisioning sencer. has to be right on. good luck Quote Link to comment Share on other sites More sharing options...
Pete M Posted December 2, 2010 Share Posted December 2, 2010 have you replaced the 160 yet? Quote Link to comment Share on other sites More sharing options...
jimoshel Posted December 2, 2010 Share Posted December 2, 2010 First replace the thermostat as previously recommended. Their are so many vacuum lines and gadgets that it is very easy to miss a bad one. First remove the vacuum lines, one at a time, from the manifold. See what the motor does. That should give you a clue as to which lines to look at closer. Block the opening on the manifold. With the importance vacuum plays in the system now a vacuum tester is nice to have. One with a hand pump to evacuate the line and a gauge. Quote Link to comment Share on other sites More sharing options...
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