Help diagnose a bad idle

[anti_flag_army]

Hey guys, so my friend just picked up an 89 coupe that needed a little love, and we have been going through it fixing various issues. One we cant seem to get is the rough idle with a slight miss. I will start out with what I have tried, and hopefully you guys will point out something obvious that I missed.

First we started with the error codes and gave us code 45 (leaking injector) I swapped some known good injectors and got the code to go away. (idle still bad)
Next we swapped o2 sensor with no change. Did the coolant temp sensor since when searching a few people mentioned that. Next were the spark plugs, the old ones were really black, swapped in some fresh ngk's. I cleaned the battery terminals to ensure a solid connection. Checked for vacuum leaks and couldnt spot any.

All of this and still we have a bouncing idle (and it smells pretty rich also) I suppose the next thing is to do a cap and rotor +spark plug wires. What else am i missing?

[240life]

This is probably not the issue, but check the alternaor voltage. Bad/ weak units can cause weird running issues.

[LoserCard]

Check timing, clean MAF, check injector o-rings, definitely do the cap/rotor/wires/spark plugs and get back to us if that fixes anything.

[LuckyX2]

Check your IAC valve too. Last time I had a poor idle, I just backed out the IAC valve screw, sprayed a bit of carb cleaner in it, let it dry, put the screw back to where it was and then my idle problem was gone.

If there's some carbon buildup in there then you're not going to be getting enough air at idle, hence the rich condition.

[Kon036]

Is there an exhaust leak? An exhaust leak can give O2 sensor readings of a lean condition because of the air getting in the exhaust stream. This will cause the fuel trim to be rich.

[JCMITO]

I have a bad Idle too. It seems all my plugs are ok. when I unplugged any of the spark plugs, I saw sparks coming out of the coil wire not at the distributor end by the other end. I"m not sure what the other end is called. it doesn't matter which plug I unplug, I see sparks coming out of the coil wire. I tuned it up about a year or so ago, but I replaced the spark plugs anyway just in case. Is the spark that I see normal? Thanks for you help.