Well it's been another 5 months with this aggrevation. I do not have any vacuum leaks. I also bought a new computer and it did not make a difference. Here's the list of parts changed.
-Several fuel filters
-new iac
-Tps with a known good one
-New dpfe (that fixed check engine light for egr)
-Mas air flow sensor with a known good one
-new egr
-Engine coolant sensor (both for the guage and computer) with known good sensors
-new computer
A crazy part about this is when I changed the parts it would run good for a couple days or weeks then start acting up again.
The current surging conditions are when I crank it at cold start the engine will not rev up for the first couple of secs like it should. It tries to, like it'll Rev up to 1500 for a sec then fall down to 500 then back up then back down. It's not got a rhythm or cycle, it'll go up and down randomly.
While driving or accelerating the rpms will still go up and down and I can feel it. It'll have a boost of power when the rpms go up and then when the rpms go down it'll feel like I have let off the gas but I haven't, then pick back up again, this too is not in a pattern or cycle it's totally random.
And still to this day if I unplug the iac I will have no surging at all. I just hate the rpm being so low at cold start (400-500). It just barely runs. But when engine warms up it'll idle at around 700 like it should.
I really don't know where to go at this point.
I've had an idea of is there such a thing as an inconsistent vaccum leak. For example, the vaccum that that runs the heater control valve is turned on when the climate control knob is on max ac or off. So is there more electronically controlled vaccum lines?
Or if you know of a different possible answer please respond. Thank you!
Also I've been thinking about. keeping the iac unplugged and adjusting the idle screw up some to make it cold start idle a little better but then I don't want it to be idling too high after it warms up.
So I don't really know what to do.
