lance6161

Hi, I drive a 03' Evo 8 which currently annoys me a lot with an unstable idle --I need to give some gas to start when the engine is cold, after start Rpm is around 500-800 (But very often I need to step on gas to maintain idle after start or car stalls), after freeway warmup Rpm rises to 1500-1900, when A/C is on Rpm falls back to 800-900 and may climb up back.


Here's the story:

A month ago, when I was on the way to Speed Element located Performance in San Jose to get a tune, at a red light, the car just stalled right there.

The car was diagnosed as "will stall when left off the gas pedal" at the shop and mechanic there said it was because of the BOV, and the aftermarket alarm system might affect the whole circuit to start after car stalls. Then they replaced BOV with Synapse DV001A.005 also along w/t OEM throttle body seal gasket. Meantime, the mechanic performed a diagnosis and developed followings:

-Performed a boost leak test after throttle body seal installed and found car was over boosted under load at about 2 bars (30psi), however the stock is 19psi, (recommend customer to get pre-tune diagnosis and tune
-IAC valve not functioning properly while A/C is on and when car is under load

Mechanic after that fixed the followings:
-Tightened loose throttle cable to allow car to idle
-Fixed several boost leaks


To save budget, I decided to do what I can do in garage. I'm capable to replace the IAC valve, but to tune up solve the over boost I know I need to bring car on dyno...

I ordered new (not OEM but fits 03' Evo 8) IAC Valve and replaced the old one. Also I cleaned up the throttle body along w/t MAF sensor. A half a month drive to let ECU recognize the new part, the car still performed as described in the beginning of this article.

Because thing's not going what I'm thinking going, I brought the car to a friend's shop where I used to get car tuned and serviced, he found a new problem --the Throttle Body Position Sensor is dysfunctional, symptom is I unplug the sensor when car is under idle, car won't stall.

So I ordered new part and let him replace it for me. Not sure if the car stalls when unplugs the Throttle Body Position Sensor or not, but still, the problem is there. My friend told me he's done with the idle by adjusting one of the two bolts (one broke and left in plug)


of the throttle cable and for some reasons I'm not sure, he suggested to replace throttle cable but I didn't.


Here we go, I want to know what the hell is going on so far with my car... Does anyone have similar experience? Should I replace the throttle cable? Please help me... Because the car is almost due to Smog... Any advice would be extremely appreciated!

Bhsj13

mods on your car? mileage? is it tuned properly?

Cal City Evo

iTrader: (13)

What kind of vacuum are you getting at idle? If it is low as I suspect it is you most likely have had the timing jump a tooth. Pull off the cover and check your timing marks. I bet you are off a tooth on one of them.

That's not how to adjust the idle either. Man talk about hokey. Shame they got over torque happy on that small bolt. Hope you have enough sticking out to be able to remove it without an easy out.

heavens turbo

do you have the factory maf sensor? unplug that and see if it will idle. any codes in the ecu? need a list of mods and stuff done to the car, along with some more info. good luck.

lance6161

Thx for replying.

As far as I know, the car is almost stock now... Only few mods like Defi boost gauge and control, Defi HUD, downpipe, moded catback (stock muffler), and WeaponR oil catch can.

Car has just reached 90000 mi and I suppose these mods work properly.

lance6161

Very much thanks, very useful info dude! I did notice a noise coming from timing belt when car stars.

lance6161

Thx dude, and car has no code so far. But as far as I know mods are few, boost gauge and control, downpipe, catback, oil catch can and that's it...