[Guest]

Three times now (in 3 months) my Evo V has pulled up like a horse refusing to jump a fence! It scares the crap out of me, because it has to be bad for the engine.

Each time the situation has been identical - close to 7000rpm in 2nd gear. There's a kind of 'pop' similar to a backfire and a massive loss of power. I ease off the gas immediately and it all goes away. At first I thought it might be something to do with a speed restricting device, but it wouldn't make sense for that to be based on rpm (?). Then I thought maybe there's some kind of rpm restrictor - but why would this kick in just below the red line?

I've done a lot of searching of old threads, and it sounds to me like it must be a fuel cut. But this seems to happen when people have made modifications to air intakes/exhausts/etc. My V is completely standard, so it can't be caused by this. I've seen some posts that suggest it could be caused by a faulty/rusty wastegate actuator, so I'm guessing this is the first place for me to look.

Does anyone know if I should expect this problem in a standard Evo? Is it common?

I need some help here. Although I used to always do the work on my own cars, 17 years of company car ownership have put me back to the 'retard' class for motor mechanics. The last time I did any work myself, cars had carburettors and manual windows!

 

[Guest]

It does sound like a fuel cut and for a standard car then the obvious place to check is the wastegate actuator.

I had the same problem on my standard Evo 6 and it was a rusty actuator.
The problem seems to be fairly common due to Mitsi's brainwave idea of mounting the actuator in the location they did and it is very handy for collecting water inside and rusting and then sticking.

Andy

 

[Guest]

Thanks Andy. I'll check this out.

One more question though.

If this is the cause, wouldn't it happen either:
(a) every time the rpm hit the offending level; or,
(b) at completely random times?

Once again, please forgive my ignorance here. I appreciate any help.

 

[Guest]

Red,
It will happen at intermittent times because the fuel cut is triggered by a certain mass of air flowing past the airflow meter. It calculates the mass from the outside air temperature and the air flowrate. Due to the density of the air changing with hot and cold weather, humidity etc etc, the fuel cut will not occur at a particular rev limit or at a particular boost level.

Hope this clears things up

Andy

 

[Guest]

Original Post:
Thanks Andy. I'll check this out.

One more question though.

If this is the cause, wouldn't it happen either:
(a) every time the rpm hit the offending level; or,
(b) at completely random times?

Once again, please forgive my ignorance here. I appreciate any help.

The AFM is a Karman Vortech. When the frequency of it reaches 1700 Hz at a certain air temperature and barometric pressure, the ECU cuts off the fuel. This is typically around 1.2 bars at 20°C outside temperature.

If you reach that boost level on a stock Evo, chances are you need a new actuator.

 

[Guest]

recently had my actuator changed . symptoms were most obvious in 4th gear with foot to the floor from 2k revs as soon as it came on boost cut would happen then the power felt wavey after that. it was rusty and the arm was not central within the actuator so it was also binding.

 

[Guest]

If you reach that boost level on a stock Evo, chances are you need a new actuator.

Dammit!!

Thanks for the info guys.

recently had my actuator changed.

Robert,
What sort of cost is this?

Dave.

 

[Guest]

Dave,
If the car still has a warranty then it will be replaced under warranty. If not then it's £145.75 from co-ordsport for an E5 actuator looking at their website.

Andy

 

[Guest]

Get yourself a good boost gauge fitted - if you haven't already.

 

[Guest]

Andy/Claudius,

Diagnosis correct. Had my actuator checked yesterday and amp; it's leaking.

Next time I'll try to come up with a harder question for you. I guess that one must have been too easy!!

Dave