Hey guys I need some help with this one. I am having an idle surge issue since my fresh build. I have a street port with power FC, professionally tuned. I figured out that this surge issue is temperature related, whenever the temp reaches 220 the surging starts to occur. As soon as temp drops to 210 then the idle returns to normal. What is actually causing the surge to occur? ECU logic related, a mechanical issue? Happens with IAC valve connected or not connected. How could coolant temp cause an idle surge? Looks like 220 is within normal operating temp, only gets up to 220 when Im on it for a bit. Really dont know what direction to go on this one?


http://www.youtube.com/watch?v=Ix8mH...&feature=g-upl

 

What rpm is it bouncing between? what injectors are you running? What other mods do you have on your car?


Either way, I think getting to 220 is a bit high unless your all out racing in the middle of summer in the desert and even then I'd take some steps to reduce the temp back down to a more reasonable but still high (to me) 210. If your on it for a little bit and temps go up that high, I'd hate to see what would happen if you were really on it on a track or on the highway in summer.

Personnaly, I ususally see temps of about 180-185 around town and perhaps up to 205 when I do hill climbs at higher boost levels on hills which are about a constant 35 degrees (some parts even steeper) for about 3 miles getting up past 85mph (I think a bit hard on the car seeing as the speed limit is only 20-25mph. there are some curves so there is a lot of hard braking and full throttle acceleration hehe ). Even then, after about 15-20 seconds of idling/cruising downwards at the top of the hill, my temps come back down to 190-195 pretty quick and I have my water temp gauge right in front of the thermostat so its pretty on the ball.

Try a new/larger/double pass radiator, ducting, modifying fans, modifying coolant mixture/type, getting that new style/nice looking waterpump which seems to be more efficient and possibly might give more hp, modifying the thermostat or switching it out with one with a lower temp at which it opens, ect. Cooler engines (up to a point) last longer in general so why not have a bit of a cooler running car?

are you 100% sure you dont have an intake leak some place? Perhaps the high heat is warping something? you can try to use a little bit of starter fluid around all the connections (make sure to have a CO2 fire extinguisher ready though or something to snuf the flames out if you do get a flare up) to see if the idle changes when it starts to surge.



P.S. you might wanna check your brake fluid level, it seems low to me.

 

Thanks for all the info skunks! Well, the good news is my a pillar temp gauge is waaaaaaay off, I should have just been watching the temp on my Power FC commander. Tonight when my a pillar gauge stated 220, the commander was at 183....whew! Seems like the idle issue is going to be related to my IAC valve. With it connected the idle surges like crazy all the time, with it disconnected it will not surge until the temp gets over 180. Im going to try and clean it, is this an issue that sounds familiar?

Oh, and to add another problem to the list, I now have an issue with no boost at times. If i get on it a few times the boost will completely drop off, not even 1 psi for a min or so....then all of a sudden full boost will come back online. Seems like a stuck vsv or something...Im going to do some homework on this one. Does this problem sound familiar to anyone?

I have so many bugs to work out, haha!

 

I had a car once with a bad Throttle Positioning Sensor that did exactly that. Can't picture in my head where it's at though.

 

without seeing any data from your ECU, I'd say your fans are coming on at the default 105C (220F). Then you are going into electrical load idle mode and you are getting an idle surge. If that's what's going on, it is a common problem. I have discussed it extensively in a few threads. It's something that requires tuning and usually careful adjustment of the throttlebody.

Also sounds like you have a failed check valve in your sequential turbo system.

 

Thanks so much, I will look into that.