1991 with rough idle and ride

[jcaceem]

Hello,
I am trying to track down a problem with my 240sx. It was driving fine then out of nowhere it started running VERY rough--so rough the whole car shook.

Thinking I might have gotten some bad gas I ran most of the gas out then added injector cleaner, sea foam, and filled up with high octane. I also replaced the cap and rotor which needed replacing.

The car runs better than before but still rough. Sometimes has good pickup, sometimes not. In park it will idle fine but as soon as you put it in any gear it immediately runs rough and shakes. If I drive it, it has a burnt plastic smell--not sure if that is anything.

I haven't taken it in yet to see if any codes come up but wanted to see if anyone else has had a similar issue.

Thanks!

[PapaSmurf2k3]

Might have a wiring harness getting burned somewhere. Also check your engine grounds. There should be one at the back of the head that goes to the firewall, and the big one from the intake manifold to the battery (I think).