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evo 6 suddenly running lean at high rpm

28K views 150 replies 26 participants last post by  Gary @ APT 
#1 · (Edited)
So had my 6 at dynotech today having issues with the car suddenly running lean high rpms 6.5k+ at 0.7bar (ish)

have changed the fuel pump wiring to nevereverman hardwire kit
changed to new walbro pump
changed to known good fpr
tested injector resistor pack all resistance is coming back 6ohms so all good
new 8mr bov
new sas gasket
new fuel filter's
new avcr solenoid

will be looking into the condition of the main fuel lines from tank to engine bay as the cars had shell swap and possibly slightly bent in the process
also has evo 4 fuel tank

will be doing boost leak smoke test & checking fuel lines from tank to engine bay
thought id ask the mlr massive advise where else to look :smthumbup
 
#5 ·
I'm posting this on here just in case somebody has the same problem in future

If the fuel pressure solenoid was faulty and open constantly this would leave the fuel pressure regulator open and creating a vacuum reducing the fuel pressure in the fuel rail creating a lean affect on high load on Dyno or road etc?


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#7 · (Edited)
Was actually a question mate lol! Just wanted to keep the thread updated if somebody else had the same problem

There's no easy way to test the fuel pressure otherwise I'd have done it I don't have the kit

Did check the fuel lines for kinks etc and there all good, looks like I can rule out pump,lines,filter

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#11 ·
Really need to try and get the fuel pressure tested to confirm its ok.

Was the AFR ok up until that point at 6.5k rpm?

Really need to get a log of what injector duty you were seeing in that rpm range

Is the car on a standard map?
I believe all is fine until at rpm range power runs lean and power drops off

I don't have details of injector duty I will ask Bob if he has them and I'll post them here as yep sure it's a standard map the car was a previous mlr member but never found out who

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#14 · (Edited)
ok there is still a issue with missfire it is very faint now feels more like rpm limiter than missfire and cuts in just befoure 7k 6.8k roughly it starts :smthumbdo

list if items i have changed

fuel pump wiring to nevereverman hardwire kit
new walbro pump
known good fpr
tested injector resistor pack all resistance is coming back 6ohms so all good
new 8mr bov
new sas gasket
new fuel filter's
new avcr solenoid
injectors tested at abbey motorsport all good readings
fuel pressure at full load around 4bar (checked on rollers at dynotech)
swapped to different maf (no change)



am starting to think are the cams out or bad valve/spring etc
 

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#26 ·
the map has not been checked the last time as you can hear the slight misfire up top

to be honest i had never used to go over 6.5k so i couldn't tell if it was related to the shell swap i finished last year
 
#27 ·
the map has not been checked the last time as you can hear the slight misfire up top

to be honest i had never used to go over 6.5k so i couldn't tell if it was related to the shell swap i finished last year
Think i'd be looking at the map, and make sure the fuel pressure is right. You say you have swopped the fuel pressure reg, was the ecu previously mapped?

Stu
 
#28 ·
The fuel pump & std reg have been changed.
The FP solenoid was bypassed.
Another fresh fuel filter was installed.
Fuel sample showed signs of contamination (black particles)
The map has been checked at that rpm.
The engine just starts to misfire & lean out @ 6-6500rpm even at 0.8 bar
Craig has checked all the fuel lines for restriction but the fuel pressure does not drop & has been checked under load.
I am sure Craig has also hard wired the pump.
Craig has had the injectors tested & said results were fine.

I still suspect it may be the fuel tank as when Craig done the shell swap a Evo 4 fuel tank was used. :confused::confused:

Most mechanical items have been checked or changed. Now Craig must have to check Electrical components to eliminate them.
 
#30 ·
the 4 tank was in very good condition thats why it was used over the previous fuel tank

could one or both of the camshafts being out slightly cause a misfire :confused:

could use a little advise where to look next guys, any input welcome :smthumbup
 
#31 ·
So I have been on evo scan looking for clues to my miss fire

Evo scan shows my o2 voltage is basically sitting at 0-0.1v and confirmed that with a multimeter at the sensor
with a/f ratio sitting at 10.2 or less with a stand alone gauge (signal from ecu)

I'm guessing the sensor is needs changing

I have a 4 wire o2 sensor
Question is will a sensor for any of the evos 4-10 work and fit in the elbow housing?

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#34 ·
Thanks chaps, fingers crossed it's over fueling and causing the issues

One other point I changed the cam angle sensor yesterday and there was a small amount of oil on the sensor itself is this normal?

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#35 ·
Update on this

Tried to start the car this morning and wouldn't run with the cam sensor I replaced the night before

Stuck the old one back in and fired up no problems?
It does have later e7 cams inside

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#36 ·
OK so I have ditched the fuel pump hardwiring and reverted back to stock
First picture is normal cold idle


Next is with fpr vac line removed



Still having high rpm hesitation/miss fire around 6.6k on

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#130 · (Edited)
From earlier on.



Spec.

OEM Fuel rail pressure for future reference



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So from that, there's 39 PSI at idle with the vac line on
46 PSI with the vac line off.

The spec is 33 and 43 PSI, so 6 PSI too high at low load and 3 PSI too high at medium load.
How can 6 PSI error be acceptable?
So rather than fixing the pressure, the flock of sheep method is to try to fiddle with the software to try to make it work?
Then doing that they create another 6 problems which end with a part out.

Just because a flock of sheep has no idea and they all do it?

Later models?
That's why Mitsubishi use 2 speed pumps, to lower the flow at low load.
If you fit a bigger pump that draws more current then the resistor should be changed to suit the bigger pump.
Most newer cars these days use PWM control of the pump along with a fuel pressure sensor.
That would be the smart way to control it.
One of my own cars, it's 3 stage with 2 pumps.......perfect regulation.
 
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#37 ·
So speaking to couple of garages today seems the only possible outcome could be map is off and needs tweaking or both the maf sensors I have are faulty?

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