Evo 4 Speedo Bounces & Engine Cuts

[sarobowe]

Hi all, hope someone out there can give me a bit of info. I own a 1998 Evo 4 which is standard apart from Exhaust and Tein suspension. I have noticed lately that the speedo needle is bouncing now and then. It seems to be ok once you are at a steady speed but when accelerating the needle can bounce up to 100 mph even if you are only doing about 40 mph. It never seems to bounce lower than the speed you are doing though. Also on a couple of occasions when i have accelerated hard the engine holds back very visously like the fuel has been cut, and if you wait and accelrate again it will do it again, but then 5 mins later its fine. a friend of mine suggested that it could bethat the speedo bouncing could be the KMH-MPH convertor playing up and that could that be causing the engine cutting as in if the needle hits max spped could it be kicking in a limiter, i cannot confirm that the needle is hitting max as when i do accelerate hard i am more intersted in looking out for blue lights. In the past i have had limiters kick in but they read from the rev counter but i suppose this could this be different. Any help would be greatly appreciated, thanks in advance. Rob

 

[1982ollie]

Hi There,

At a good guess it does sound like you have a problem with your electrics/speedo converter. Hold tight, as some more friendly help will be on its way.

However the fuel cutting could be a separate issue altogether - My evo 4 was recently fuel cutting, but that was due to my actuator sticking, therefore I was over boosting. This can be fatal to you engine. Do you have a boost gauge??

 

[sarobowe]

HI Ollie, No boost gauge fitted. do you think its worth just fitting a new actuator, if so would it be good to go for a standard item or aftermarket. Also not sure if it is related but i do get it missing so to speak sometimes on steady throttle as in if i am driving at 40mph you get a little miss but obviously on steady throttle it's not really boosting, it has had new plugs etc and there are no DTC present. Thanks Rob

 

[1982ollie]

Rob,

When you put your foot down in third or fourth - Do you every get a sudden fuel cut? i.e. Almost feels like hitting a brick wall.

Cheers

 

[sarobowe]

Hi Ollie, EXACTLY that, but have had it in 2nd and 3rd, then i realise she is not happy so i slow down a bit, strange though as it doesnt always do it, but has happeneda few times, biggest time i noticed it was accelrating joining on to a motorway in the end had to slow up behind a lorry . Rob

 

[1982ollie]

Rob,

Sounds like you are getting some kind of fuel cut. Here is some info I have found for you which should help:

Fuel Cuts
Cars affected:
Lancer 1800 RS/GSR, Evo 1-7

Symptom:
A very sudden de-acceleration due to the fuel being cut to the injectors, similar to your foot slipping off the accelerator except it will recover almost immediately. It occurs if over boost is detected while accelerating hard (common at roughly 4000rpm in 2nd, 3rd or 4th gear but possible at other rpm and gears). Also it is more common if the outside air temperature is colder.

Problem and cure:
Fuel Cuts are the Engine Management's way of stopping serious over boost situations occurring. Instead of detecting the actual boost pressure the ECU (Electronic Control Unit) uses information from the Air Flow meter to work out the boost pressure. The ECU will cut the fuel at roughly 1.3 bar boost pressure (18.8 PSI) on the Evo 6 (approximately 1.5 bar on the Evo 7) but the specific cut point is dependant on atmospheric conditions at the time so it will not be the same from car to car. Fuel cuts are more likely to occur in winter as the air is colder and therefore more dense. Early Evo models may have a lower cut point that is in relation to their standard boost pressure level setting.
Fuel cuts commonly occur after fitting an upgraded aftermarket induction kit and/or exhaust due to the increased air flow they create but fuel cuts have occurred on standard cars before. It is also possible for fuel cuts to occur due to a faulty Wastegate Actuator but it is not that common (see elsewhere).
Do not live with fuel cuts! The sudden cutting of the fuel sends a shock through the engine and drivetrain which in itself can be harmful. You can temporarily 'drive around' fuel cuts by avoiding using full acceleration or if very worried keeping below 4000rpm at all times (as if you were running in the engine).
The cure for fuel cuts depend on what is causing it and also what you intend to do with your car. If you believe the over boost is due to any upgraded parts that have been fitted then the boost level can be dropped fairly easily by a manual alteration to the Boost Control system, although dropping the boost obviously partially defeats the object of fitting performance parts. If you intend to modify your car further then you will require an upgrade to the Engine Management to either eliminate the cut point or 'work around' it. It is not recommended that you use a 'Fuel Cut Defenser' as they tell the ECU that the fuel cut point has not been reached by electronically reducing the air flow signal and this can lead to a lean mixture as the ECU will reduce the fuelling to suit. If you are having problems with fuel cuts then consult a qualified garage/mechanic that knows about Evos and also let them know what you intend to do with the car in future.

Approximate cost of repair:
Depends on the fault.
Adjusting the boost level down slightly will take 30 minutes with no parts required.
A new Wastegate Actuator is approximately £200 inclusive (plus fitting approx. 1 hour)

 

[sarobowe]

Hi Ollie, cheers for that, looks like t and the actuator could be the problem, i have found an o/e part on ebay for £110 so might go for that as i would like to keep the car standard as poss. And get a new speedo convertor at the same time and fingers crossed will fix everything and i will let you know. Cheers again for all your help, never know you might see my sitting at the side of the road with a blown engine as you are not that far from my neck of the woods. Rob

 

[1982ollie]

Lol - Hope not mate - Good luck - If you still have probs, get back to me/us here.

Cheers,

 

[ElDopesta]

Well done Ollie!

I suggest that you locate the converter on temporarily disconnect it to see if the Speedo operates correctly. You will find either near the gearbox or in the engine bay attached to the bulk head somewhere. The last place to look would be behind the Speedo Cluster.

Let us know how you get on.

El

 

[sponners]

speedo issue does sound like a convertor problem (quite common with the older ebay cheapies)


first thing I'd recommend you do is fit a boost gauge (even if temporary) and find out what boost your hitting to determine whether you are overboosting your engine or not.........which could end up in tears if it carries on.

 

[Dave Brennun]

How you gettin on with this pal?