So I have a 90 loyale and I'm at a loss. I can't seem to figure out what the problem is. I really have 2 problems. So when I'm sitting at idle, my rpm's fluctuate between 500 and 900 rpms, and the car visibly shakes like a spark plug is out or something. If I drive for a little while, and come to a stop it stas around 1000-1200 before dropping down to fluctuate. I have no check engine codes anymore, I just fixed the light which led me to the egr solenoid, found a working one at junkyard. No visible vacuum leaks (I just resealed the motor, so when I pulled it I checked every vacuum line that is associated with engine removal). the other problem I have is my voltage likes to drop whenever I turn anything on that requires a bit of juice. I put a new alternator in it and that didn't fix it, so I know it's not that or the voltage regulator so I'm pretty sure it's a dodgy ground somewhere in the dash or something. I have brand new thick ground cables to the engine and one from the engine to chassis, so I don't think that's where the ground issue is at. Could the two be related? The other thing I've noticed is that I get maybe 20 mg city, and I'm pretty sure I should be getting more. It's a 4wd 5 speed manual, and despite them getting less than fwd models I should still be getting a bit more than that. So any thoughts guys? I'm completely stumped. The only thing on the drawing board right now is that the purge valve might be stuck open, but I hear it clicking when I turn the key and it has continuity. I've read that a stuck purge valve is like a huge vacuum leak though so it's a thought. 

My '89 has similar symptoms. Following this thread. 

 

John

Same thing with my 88.  Any time I turn on the wipers or blower at idle, I can here the idle change and watch the lights dim.  I also have the fluctuating idle, more so when its cold though and has been sitting overnight.  But it comes and goes and I still get fluctuation and a bit of a stumble occasionally when its warm out.

I should look thru the archives and find that thread about the Nissan alternator upgrade...

 

John

Same thing with my 88.  Any time I turn on the wipers or blower at idle, I can here the idle change and watch the lights dim.  I also have the fluctuating idle, more so when its cold though and has been sitting overnight.  But it comes and goes and I still get fluctuation and a bit of a stumble occasionally when its warm out.

Yeah this literally describes my car. I don't get it I'm stumped.

UPDATE: So I replaced my coolant temp sensor (the green plug) and it made a pretty big difference. If it weren't for the fact that I have voltage issues too it probably would have solved the problem entirely. But now my rpm drop is not as erratic. It will stay where it should until the fan kicks on, in which it will drop to 400-600 rpms and start to shake like it used to. I've also noticed that everything else will drop my rpm when turned as well, like my brights or blower motor full blast. I know it's not my alternator nor voltage regulator, so at this point I'm leaning towards either a dodgy ground, positive wire trouble, or a short somewhere. Although a vacuum leak is still a possibility. Any ideas on where I should start on this?

Did you see the post a while back about using a small propane tank to find vacuum leaks? I'm going to try that...

 

John