Hello all,

I recently encounter this problem with my car. After driving for about 30mins when the engine is nice and warm, I can feel occasional engine jerks when I accelerate, the rpm will dip a little. Even more apparent when I accelerate harder. After that when the car is stationary and rpm is idle, the engine will just suddenly stop running and I will have to restart the engine. This happens for about 2-3 times during a 30-45min drive

Self diagnostic with my degree in mechanical engineering from the University of Lowyat:
Spark plugs?
Spark plug cable?

Car details:
Model: Proton Perdana V6 enhanced version 3
Year: 2007
Engine: stock V6 6A12
Engine Oil: Semi syn 10.40W
Last service: less than 500km
Last spark plug change: 1.5 years
Last alternator change: 3.5 years

In your experience, what do u think is the problem? Trying to gather some opinions before I send my car to the workshop because I know this can potentially be a few problems and some mechanics will use the trial and error method to replace a few stuffs first before finding out the actual problem. I don't want to waste time and money.

Thank you for your input in advance!

This post has been edited by RS42: Nov 21 2018, 08:53 PM

Try look at the alternator.

I thought alternator problem is only when you try to start the engine, not while it's running?

But thanks for the input, I will include it in my details.

Did it occur when you don't switch on aircond? I know this is difficult for some segment of the society that would melt without aircond, but just try.

Throttle body problem. Common issue for the v6s

Lol I can give it a try.. but what's your reasoning for this?

I have another friend driving a V6 with a pretty similar problem too.. the difference is that his engine does not stop. The rpm just dips really low and would rise back to normal again. These 2 issues are similar issues due to the throttle body?

His mechanic said it was due to the throttle body as well. He hasn't got it fix because it doesn't really bother him lol but mine is dangerous.

This post has been edited by RS42: Nov 21 2018, 09:55 PM

Suspected throttle body problem.... specifically the ISC part.....

I think v6 is using stepper motor type. if it is bad, just change the bottom half set. some1 in marketplace is selling it.

lsm1991

Idle problem mostly related to throttle body problem...the isc gear/stepper motor inside is in bad condition already.

Try install FICD to helps it idle...many 4g series owner use it to solve idle issue

start engine, battery. alternator while running..charge the battery and run other electrical/electronic stuff.

Firstly, what is the ISC part?

I tried driving in the morning with the AC off and all was fine.

ahh oops thought i was replying to someone else*

This post has been edited by lsm1991: Nov 22 2018, 01:33 PM

alternator is basically what is supposed to power the car once it starts running. if the alternator is dead, the battery has to do all the work (it cant for long)

theoretically if the alternator is dead, u wont be able to start after that.... and after jump starting, car will die soon after jumpstarting


mines not exactly the same engine (mines terbalik) but yeah common issue on mine, replaced it 3x in 2 years. I assume the perdana employs the same device? Usually results in a crazy idle and can be very difficult to start the car cold.
the isc aka 'idle speed controller' on mine has no gears, just a electronic stepper motor controlling the amount of air bypassing the throttle.
its a brown (or black) cylindrical thing just under the throttle body. (just directly under the throttle body, there should be a wire connected to it).

if its a spark problem, you should hear the car missing. quite difficult to troubleshoot unless its a constant misfire on a particular cylinder cause Mitsubishi idiotically put 3 F#&$@#& sparkplugs under the F%@#&@ intake manifold. (i dont think this is ur issue, car should not die even if its on 4 cylinders)
*if its a constant misfire, you can actually listen to the misfire but cabuting the plugs till you find the one 'not contributing'

other potential issues.....
-maf? could be dirty, can cause all this
-vaccum leak also causes the same issues

This post has been edited by lsm1991: Nov 22 2018, 01:51 PM

ISC aka Idle Speed Controller is located at the lower portion of the TB and your ECU uses it to maintain a stable idle engine speed when extra load is exerted on the engine for e.g aircond compressor kicks in, hydraulic pwr steering system under load etc. etc. If ISC is not functioning properly, your engine will die or idle very poorly whenever these loads come in.

1 more thing.... have you been using radiator coolant all these while?

Yeah I think it's safe to say that I can narrow it down to TB problem.
My car can be difficult to start when it's cold too.

And the next question is.. how much do u think it would cost to change the TB entirely?

I've got some quotes as below:
Ori: 700-1000
Recond: below 500

I recently changed my radiator and the mechanic said to run it on water for awhile first before adding coolant. I drove for about 2-3 weeks before adding coolant.

As shared b4, you hv the option to change only the bottom half only which is where the ISC is located. Brand new set but made in china (or so I was told) though.

Price is around 400 or less for part alone..... not sure on labour charge. just search in lazada shopee lelong or here in marketplace.

Obd2 reader to read codes

Otherwise is wasting time

i really doubt u need to replace the whole thing.... just have the isc looked at




u can try all you want with this car, an obd2 reader will never connect