and people never should touch the biss screw. BISS stands for Basic Idle Set Screw. Its the base the car goes off of to keep idle there when fuel trims are 0, coolant temps at 193-205, and all acessories off. After that the ISC makes compensations for headlights, AC, and other crap. It was set a certain spot from the factory and SHOULD NOT BE TOUCHED. If you have idle problems, its turning that screw will just mask the problem, when the real problem was a vacuum leak or something. Then you later down the road fix the vac leak and now your screw is out of wack and now you idle surge. Generally it varies from car the car but the tolerance is 1.25 to 1.75 turns out from soft bottom. Taken everything else is in good working order, the car will idle damn close to perfect.

^^^^Word, even with 272 cams it will idle fine.

And you answered your own question...you touched the BISS.

UPDATE: So today, Vespor n I put in the BISS n did they adjustments. After pulling the old BISS we discovered there was NO O-Ring present. So after dropping in the new one, things ran a lot better. NO MORE SURGE! But now the idle is slightly off. When I stop, the idle sits at 1400-1600 for about five-ten seconds before dropping to either 1k or 750 rpms (BISS is set at 750). So my guess is the TPS is bad. What do you guys think?

yea i know i'm bringing it back from the dead. I seem to have idle surge too. Replaced ISC. Checked Coolant. All good so far. I put my thumb on top of BISS screw and nothing changes. So how would i check the tps? and i hear the coolant temp sensor can be a culprit too. What do i need to do to check these things?

Some more background: the surge suddenly started after i installed a new copper exhaust manifold gasket. After the gasket was installed, i started the car and sprayed a bit of soap water around the area to see if there were any exhaust leaks. After that, i noticed the stock coolant temp gauge did not work. It started working again. But the Idle surge still exists. I also have a bad o2 to downpipe gasket. Any suggestions?

do you have a logger?

i can log on my laptop on my oldschool ecuplus tuning software(yes i have to upgrade $$$$)

log front o2 sensor value, coolant temp, and tps values.

the tps seems fine: 1% at idle and fluctuates when i give it gas. also 0% when car is off and 96% with pedal to the floor. Coolant temp sensor reads right on with my aftermarket water temp gauge. front o2: what should i be looking for with that? should i be seeing if the voltage fluctuates at idle? at this point it seems to be a vacuum leak somewhere but i have no air compressor so it's a bit hard to boost/vac leak test. i guess i either beg one of you guys with one or take it to RRE and pay em to do it. And Sam.... does RRE sell mufflers that have 3in inlet with dual 3 inch outlets?