Rough Idle, tried many fixes..

[piranhamatt]

I bought a stock '89 240sx SE as a project car on Thanksgiving. A couple weeks later I bent valves in my 98 gsr, so I started driving the 240, and didn't have any problems.

When I first got it, I changed plugs, O2 sensor, water pump, brakes all around, and did an oil change. Last week it would not start up when warm, so I searched here and found my answer, CTS. Changed that and it fixed the problem. While I was at it I changed the plug wires, fuel filter, valve cover gasket, dizzy cap/rotor.

Everything went well for a few days, and last night it started idling rough. It feels a little less powerful than normal, but that could be my butt dyno.
The exhaust sounds/feels (with my hand at the tip) like a misfire. When I pull a wire or injector from the head, it starts bogging, and goes back to the rough idle when I plug it back in. This happens on each cylinder. I'm thinking maybe it is being starved for fuel on all cylinders, so maybe the fuel pump? I'm at work right now, and trying to get ideas for when I go home.

I am still waiting on machine work on my gsr head, so I need at least another month out of this engine, and would prefer to have it a little longer as a backup car.

[bongnak]

the wire harness' are getting old by now i had a kade that had weird bogging issues too. after two days of replacing parts with good known ones it ended up being the wire harness; the head and its sharp edges cut through the loom near the tb and injector area, shorting some of the wires.

look for rubbing/shorting at the harness all over
check grounds
clean maf

[piranhamatt]

There is a junkyard with a sohc near me, so if it comes down to it I can pull the harness from it, but it will probably have the same problems. Could IACV problems cause this?

[bongnak]

yes it can clean it out with carb cleaner
oh bleed the coolant too

[piranhamatt]

Coolant has been bled. I'll clean the IACV and MAF tonight, and probably the throttle body while I'm at it. I'll post back with results.

[beetlejuice]

While you're at it, check for vacuum leaks in the bundle of hoses between the intake manifold and the firewall...

...other than the harness or IAVC, that may be your stumbling issue.

Good luck.

[Style]

check your spark plugs and make shure tey are gaped right.

[piranhamatt]

I did all of the above, and it helped the idle, but now my slightly ticking engine has turned into a knocking/heavy rattling. I fear this engine's days are numbered.