Evo 8 idle problem Please help!!!
Feb 11, 2012, 08:49 PM
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Evo 8 idle problem Please help!!!
Whats goin on guys? my evo 8 has some kind of idle problem that seems to be kinda common. i can start it up and it idles 1500 rpms which is fine. i let it warm up to operating temp and it drops to like 850 rpms and its perfect but as soon as i rev it up and take my foot off the gas the idle drops to 200 rpms and then rises back up to 850 shortly after. if i drive it on the street it stalls at stop signs and such. now i've read a ton of threads just like this and i've checked everything they have said and the problem still isn't solved.
i have cleaned the MAF sensor, cleaned the throttle body and intercooler piping, replaced the first O2 sensor, replaced the CAM position sensor, cleaned the IAC which the teeth are slightly warn on but look fine, checked injector resistance, played with the BISS screw, changed the fuel pump, checked the ECU with a scan tool and we're getting no trouble codes and readings from all sensors but it showed there is a fault in the system for EVAP EGR and CAT.
Now the guy i bought it from said it was running 100% before he replaced the stock exhaust with a turbo back ti-c greddy 3" all the way back with no cat. could changing the exhaust really have this kind of effect? i feel like I've checked everything else! PLEASE HELP
i have cleaned the MAF sensor, cleaned the throttle body and intercooler piping, replaced the first O2 sensor, replaced the CAM position sensor, cleaned the IAC which the teeth are slightly warn on but look fine, checked injector resistance, played with the BISS screw, changed the fuel pump, checked the ECU with a scan tool and we're getting no trouble codes and readings from all sensors but it showed there is a fault in the system for EVAP EGR and CAT.
Now the guy i bought it from said it was running 100% before he replaced the stock exhaust with a turbo back ti-c greddy 3" all the way back with no cat. could changing the exhaust really have this kind of effect? i feel like I've checked everything else! PLEASE HELP
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hermesevo8 (Apr 17, 2016)
Feb 11, 2012, 11:31 PM
#5
boost leak
bad idle air controller
if theres wear on the gears on the IAC it needs replaced.
if you changed the BISS a lot you have now altered the
ISCV tables in the rom physically.
if you dont have a boost leak tester get one asap! its your best friend with a turbocharged car.
bad idle air controller
if theres wear on the gears on the IAC it needs replaced.
if you changed the BISS a lot you have now altered the
ISCV tables in the rom physically.
if you dont have a boost leak tester get one asap! its your best friend with a turbocharged car.
Feb 12, 2012, 11:04 AM
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we did a boost leak test and everything was fine, we tryed turning the biss screw by quarter turns one way up to a turn in a half. no help, so we put it back to stock and turned it a full turn and a half the other way quarter turns at a time and it was no help either so we put it back to stock again.We sprayed carb cleaner on every vacuum line we could find and the idle never raised.My blow off is recirculated. the guy before me changed it to an AP blow off, i have a K&N intake and the exhaust, everything else is stock. i think were going to change the iac today and see if we have any luck. Tomei_evo8 do you have an exhaust with no cat or is it stock? thanks guys ill let you know what happens.
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Feb 13, 2012, 10:45 AM
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Ok i replaced the iac still no help, turns out it was the blow off valve. It was all sticky. It barely opened and it sometimes wouldnt close. We got rid of that recirculating **** and poped another bov on it and we had no more problems. I cant believe it was something so simple.
Aug 10, 2012, 03:59 PM
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Hate to bring this back from the dead but my car is having a similar issue. The wideband shows erratic a/f ratios at idle and is rough idling. Replaced the iac and also replaced the front o2 sensor as i know it was bad. wondering if my bov is the issue like it was for TS. Any way to test your bov?
Aug 4, 2016, 03:32 PM
#12
Ever figure out what your problem was I'm having a similar issue... replaced iac and no change, however I found a slight boost leak at the injector seal on only one injector wondering if that's the cause
Oct 16, 2018, 08:10 AM
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yes i replaced my idle air control valve with a brand new oem one and it made a diff but i still get that drop in rpms here and there from time to time. Like i mentioned earlier it always happens when im going low speeds and i have to throw in the clutch unexpectedly. The rpms drop and my afr goes to like 15.5-16.6 and then once the rpms catch up it evens out to 14.7-15.0