Hey Guys, I'm encountering some problem on my Evo IX but could not trace the root. Would appreciate if you guys can provide some inputs or solutions.

I'm on a stock engine with a 20G turbo (boost at 1.7bar). Recently, my idling is erratic and fluctuates between 500rpm to 2000rpm. Normally, a light tap on my gas will increase my rpm to between 1,500rpm to 2,000rpm. Now, there is no reaction unless I tap more (goes up to 3,000rpm).

In the past, the car can roll smoothly on 1st and 2nd gear without accelerating. Now, the car jerks violently as though it is starved of petrol. For normal driving, I have to rev hard to move off smoothly.

A check on my plug shows that plug 1 is fouled and I have replaced all 4 plugs. Problem persists after awhile. I swap the plug cable and the MAF sensor with another Evo but problem still remains. My tuner says there is no problem with the mapping. I did a compression test on my engine and results r pretty consistent (1 - 95%, 2 - 95%, 3 - 100%, 4- 102%). Injectors are working fine as well.

My workshop suspects there could be a slight leakage from my cylinder 1 and suggested that I replace my piston. The valve looks alright as well. I very much doubt so that it is due to the piston and wonder if it could be due to any electrical fault.

I'm at my wits end as to what could be the problem. Any one encountered similar problems before?

Thanks and Cheers

 

this could seem crazy and a shot in the dark, but..... have you checked the flywheel? I had hotspots and it would cause the car to jerk violents when taking off, once moving and shifting through the gears it was fine, but the initial movement was violent. If i increased the revs to about 2500rpm it was ok, but anything less would result in violent jerking when trying to move off smoothly. probably not the reason but if all else fails then it could be that. good luck

 

Thanks.

However, it happens during idling as well so I doubt it could be due to the flywheel.

Anyone else can advise?

 

do u have a wideband? what are the reading @ idle? or when ur revs are going crazy? Happened with me once and it turned out to be something messed with the map..

 

Check the throttle body seal.

 

definatly not your motor, try and find a scan tool and look at the readings for your MAF sensor, Idle Air Control, and your coolant temp sensor. Any of those sensors will cause your car to run like it is if being faulty. Good Luck

 

Quote:

Originally Posted by evo_q8

do u have a wideband? what are the reading @ idle? or when ur revs are going crazy? Happened with me once and it turned out to be something messed with the map..

Idling is between 500rpm to 1500rpm. It can get crazy anytime. Sometimes it happens during cold start. Sometimes, it can become stable in hot weather.

My tuner has checked my map and says it is fine.

Quote:

Originally Posted by Ev0ikon

Check the throttle body seal.

Thanks will check it out

Quote:

Originally Posted by Slovo

definatly not your motor, try and find a scan tool and look at the readings for your MAF sensor, Idle Air Control, and your coolant temp sensor. Any of those sensors will cause your car to run like it is if being faulty. Good Luck

Thanks, will check them out too~

 

Have a fuel pressure gauge installed. Check pressure at idle as well as at WOT. What is your complete list of mods? You say that the engine is stock. So, aside from the turbo, what else has been modified?

 

Have you done a boost leak test? If you have a boost gauge what does it do at idle? Do you have an aftermarket bov? Is the bov venting to atmosphere?

 

might be just a vacuum leak.

 

i think i have a similar problem.
my idle jumps to 2500-3000 when ever it feels like it.
i haven't had a chance to look at it. but i was thinking that maybe a hose is loose.
my 9 mr has minor mods.
intake, intercooler pipes, manifold, o2 housing, exhaust, catless cat and cobb AP stage 2 93 oct. map.

 

^ The first things that popped in my head. Check you BOV/DV, do a boost leak test, and check for vacuum leaks.

When I bought my car, it had a greddy type-s BOV installed that was venting to atmosphere, and the car had very similar problems to what you are describing.

Good luck!

 

Been busy and didnt log in as often. Anyway, problem resolved.

It is a faulty fuel regulator that is causing the problem.