420a Idle Surge Problem, with a twist?

Hi, I have a 98 Eclipse GS 101,xxx miles. No Mods at all. I have been experiencing idle problems lately and have taken the car to Dennis Mitsu. numerous times with no results. Anyway, any help at all would be greatly appreciated.

Symptoms:

Fan OFF:

VERY rough idle
Surge from about 800 down to 300
CEL


Fan ON:

Rough Idle
Surge from about 900 down to 600
No CEL

Recently had new spark plugs and wires installed, cleaned the throttle body, and also a new fuel pressure regulator. None of it helped, of course.

[dewman0012]

well, all i can tell you is, don't go to dennis mits. i hated that place, they don't know anything. They told me to replace my spark plugs and wires because that was the reason for mine not starting. no that wasn't the case, it was the waterpump and timing belt. that pissed me off because i had to wait longer because they couldn't figure the problem out. thats just my advice about that place. also, do you run your car everyday? i have that problem for like a couple second ever so often.

[1lowDSM]

get a new tps and ics that should fix your problem

[MrBlunt]

i happen to have both of those sensors if you need them...it ocudl be those...it could also be a bad coil causing a bad idle....check the resistance w/ a volt meter and see if its in spec