Nissan Repair: rough idle and a little resistance, vacuum leaks, infiniti j30

Question
QUESTION: My 93 Infiniti J30 has suddenly started running rough or idling rough I should say. It's not as bad when the RPMs are up. There is also a squeeling belt when I take off. Hoping it just needs new plugs but I fear that it has jumped time. Hope you can help me with your expertise.

ANSWER: Hi Holly -

The squealing belt is probably either the A/C belt or steering. Inspect for shiny or frayed surfaces. If all seems well, then tighten it and you should be good to go.

For the rough idle, if it is the plugs, then it would be missing up hills or under acceleration. Does it do this? Do you have any CEL light on (check engine light)? Also check for vaccuum leaks, broken or missing lines. Is this vehicle automatic or standard shift?

Please get back to me -
aloha
calvin

---------- FOLLOW-UP ----------

QUESTION: Okay--No CEL lights. It is an automatic trans that was just replaced. We just changed the plugs. 5 were good and one was terrible and black with gas. Its running a little better but not like it should- still idling a little rough. No apparent vacuum leaks. Any suggestions? Happy New Year!

Answer
Hi Holly -

Happy New Year to you too!

The one plug that was black means that it was not firing. Can you pull that particular plug out once again and see if it is still black, or close to it? If the plug is black, it could be that the wire or coil for that plug is defective and needs replacement.

I do not think that the timing belt jumped. Usually happens only with standard shift.

If the rough idle started immediately after the transmission replacement, then I would check (or have the technician check) the re-assembly to make sure they did not forget to connect any wires or vacuum lines.

Hope this helps -
aloha
calvin