My 2004 Jeep Limited 4x2 3.7 123,000 miles has a rough idle, I have changed the plugs anyone suggest the next steps to correct problem, I have no ck eng lite and I don't know how to check each cyl coils.

15

Asked by Apr 22, 2012 at 02:33 AM about the 2004 Jeep Liberty Limited

Question type: Maintenance & Repair

2 Answers

12,035

Sounds like a possible vacuum leak. The following test is a good indicator of several major engine components as indicated by the results. Here is a good reference for vacuum trouble shooting.......... You should get between 17-22 in. hg. at idle, depending on your elevation above 2000 feet MSL or mean sea level. To perform this test hook vacuum gauge directly to manifold vacuum. 1. Low steady needle usually indicates leaky intake, a leaky vacuum hose, late timing, or incorrect camshaft timing. 2. If reading is 3-8 inches low and fluctuates at that low reading suspect an intake manifold gasket leak at intake port or faulty injector. 3. If the needle has regular drops of about 2-4 in hg. at a steady rate the valves are probably leaking. (Perform a compression check). 4. An irregular drop or down flick of the needle can be caused by a sticking valve or an ignition misfire. 5. A rapid vibration of about four in hg. indicates worn valve guides. 6. Slight fluctuation of one inch or so indicates ignition problems. 7. Large fluctuation perform a compression check. 8. If needle moves slowly through a wide range check for PCV issues. Lastly watch the needle as you rev the engine slightly. The needle should drop then rise up to a maximum then settle back down to your idle reading. Hope this gives you a good place to start and helps you figure it out.

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15

thanks I'll have to get a vacuum gage and ck it out

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