Hi, If the exhaust valve look like this, but the sparkplug has ok color. How long time does it take to get normal color back on exhaust valve? I did have bad IAC and TPS, i changed them and the MAP sensor last summer and have been running 4-5 tank of fuel. I did have vacuum leak and bad PVC valve to.
The color of the plugs and valve is from when i replaced the head gasket for 2-3 weeks ago, but maybe the color on the exhaust valve is from when the IAC was bad?.
I have now replaced the manifold temperatur sensor to, i was going to replace the O2 sensor but i cant get it loose. I did also have the crack in the exhaust manifold that i have got welded.
Since i only use the car for short trips like 15km should i take here for a longer run to get lean error code if there is something wrong? Its a ZJ 93 4.0L.

 

From the pics you posted, those valves and plugs look perfectly fine to me. Even brand new ones are going to look like that after a couple of thousand miles.
*About your O2 sensor, try to remove it when it's HOT.. after a 10-15 minute drive, or heat the pipe with a propane torch. A box end wrench is best (less chance of rounding it off) Do you have the new one already? If so, don't worry about cutting the pigtail on the old one to get the wrench on it I believe I used a spark plug wrench on mine, but it came out w/o a struggle even tho it was cold engine. (I did spray a little PB blaster on it first)
*It sounds like you suspect a bit of a lean running condition.. I'd suggest you find Programbo on this forum and upgrade your injectors to the 703's. He cleans and tests them and ships them to your door for $70 (in the US) I did this a year or so ago and it was the best performance upgrade I've done yet. Either way, a too lean condition would show on your plugs as more whitish in color.. a tan or light brown is normal. With all you've done, I'd think it's gonna run like a top!

 

So the exhaust valve dont looks like its running lean? Thats great :-) I have installed some 784 i got from Programbo :-) (but thats after the picture was taken) it was a totaly different car to run :-) Yes, i have the O2 sensor, but its a Bosch, but the one thats in there has been there for a long time i think. I have used a lot of PB but it didnt help, i will try when its hot to se if thats help. I could buy a cheap gauge to read the value from the O2 sensor, but does the value tell me anything and is there any point in having a O2 gauge? Maybe a exhaust temperatur gauge togheter with a O2 gauge would tell me something? Should a exhaust temperatur gauge be inserted before or after the O2 sensor (if i do it) ?

 

It's an engine, not a surgical tool. Stop worrying about the colors of this or that and just drive your ZJ. You're going to give yourself an ulcer with all of this crazy worrying.

 

There fine -old saying if it aint brooke dont fix it

 

I've read that the Bosch aren't as good as the original NGK or NTK O2 sensors. It might be ok, but i'd use the original if possible. I wouldn't bother with a gauge myself. The upstream (pre cat) sensor sends a signal to the PCM and the PCM uses that along with signals from other components to adjust on/off settings for the injectors. The after cat O2 sensor monitors the efficiency of the catalytic converter.
I agree with what Bustedback said above.. if somethin' is obviously wrong, fix it.. but no use checkin' every little thing. It's never going to be perfect.

 

Its only one O2 sensor on my engine. But to see if its working i need to use a gauge? Or could i trust that the PCM would throw a error code?