Nz new 98 wrx misfire problem. FIXED :)

[vr4ex]

I have a 98 Nz new wrx and i cant get it to perform correctly. This car is 100% orgional and un molestered. The problem is that it missfires under boost, even light amounts of boost and blows lots of black smoke. Could be due too the misfire or over fuel could be the cause of the misfire? This Car starts and runs mint otherwise. Now being a trade qualified auto mechanic ive been in there and replaced the obvious items. New plugs gapped to 0.7mm, new leads, and New airflow meter. Still no fix.

So ive swapped the throttle body assembly (tps and iac), coil pack, map sensor, knock sensor and even went to the extent of sourcing another ecu as a jap one wont even run the engine. ive checked all vacume lines, checked fuel pressure and flow. Checked and replaced cambelt.

Have had it on a scan tool and seen the live data and couldnt see anything wrong.

Ive only really got o2 sensor, cam/crank angle sensors and injectors left to change.

Anyone got any ideas except a box of matches.

[Timmah]

When changing the parts that you\'ve changed, did you reset the ECU at all?

That\'s the end of my knowledge.

[Kiwi_Fozze]

silly question, but have you replaced the fuel filter? might be restricting fuel flow due to blockage (stab in the dark)

[vr4ex]

Reset as in unplug over night or Plug the plugs together and drive up the road?

Fuel filter is new aswell.

[Kiwi_Fozze]

plug plugs together, will flash error codes too, but best way to reset.

[vr4ex]

Did that last night, Its never showed any error codes. Will do again tomorrow and swap whats left to swap.

[Timmah]

Did the scan tool show the injector readings while under boost?

[vr4ex]

Showed the duty cycle but i had nothing to compare it to. Can put back on scan tool anytime.

[tebbyj]

Tricky one...

Black smoke suggests its over fueling, you\'ve checked fuel pressure and flow i\'m guessing that all checked out. Did it start doing it randomly one day or did you get hold of it like this?

Has it got the right injectors for the ECU being nz new they are smaller from memory? are they all working correctly? Fuel pump pumping properly?

O2 sensors have a large effect on subys before replacing it try checking it with a graphing multi meter (if available) and check cross count vs voltage readings.

Other than that all i can think of is a wiring issue somewhere...

[vr4ex]

Got hold of the car with heating issues. Have got that sorted but cant get to run sweet. It looks like the motor has never been out or apart. Has got yellow injectors And have most likely never been out. Have checked fuel flow and pressure with 15lb of pressure on pressure reg. Ill rip injectors out tomorrow and check or swap. Havnt got access to graphing meter.

[Guest]

Are the yellows stock in it? just a thought. It wouldnt be the first time someones changed out injectors but car looks stock. What code is the ecu and what colour afm? Is it V4 centre coilpack or V5 offset coilpack?

[vr4ex]

Its a v5. With Td04 turbo, yellow injectors., 260km speedo etc. Afm is the 2 screw replaceable unit as standard in v5 style engine..

[Guest]

What was the code on the ecu case? Just curious. Sounds a lot like ignition breaking down under load. Wiring all good for the coil pack?

[vr4ex]

Black sticker E3 ecu. Im thinking the same thing as id swear it is a ignition fault. will be checking wiring to coil over weekend.

[madmike]

also check engine earths... the manifold ones in particular

these can cause all sorts of havoc with the ignition system..

[tebbyj]

I thought TD04 nz new cars had grey injectors... i may be wrong

What were the plugs you pulled out like? wet, oily, carbonated or anything like that?

[shore_boy]

 tebbyj said:

I thought TD04 nz new cars had grey injectors... i may be wrong

What were the plugs you pulled out like? wet, oily, carbonated or anything like that?

+1 I thought the WRX came with grey injectors and the STI with yellow.

That\'s tough mate, I\'ve had recent fueling issues too. if she\'s boosting and constantly trying to reach full boost then from my experience issue is mechanical. If it\'s being limited/cut at any stage then electrical. Also every time I\'ve had this I get what seems to be a miss fire but i reckon just an extremely rough idle?

Unfortunately you\'ve covered all of the problems that I found with my car.

I know it doesn\'t sound fantastic to push the car into boost when the car is running badly but this is how i\'ve diagnosed this issue in the past. Could pay to check boost gauge readings at idle and under acceleration?

Just my 2cents. All the best.

Quick question, what is the reason the Japanese ECU won\'t run the car? Just curious.

[vr4ex]

So today ive changed cam and crank angle sensors which I knew wouldn\'t have any affect. Checked engine earths. Checked earth and power supply to coil and also jumped the power supply to the coil straight too the battery. Checked the spark from the coil, which is pretty agro. Wouldnt want to get a boot from it! As for injector colour im not sure but yellow seems to be the norm.

Jap ecu plugged in but it did nothing. No fuel pjmp or anything.

Plugs were black with dry soot.

[Guest]

 tebbyj said:

I thought TD04 nz new cars had grey injectors... i may be wrong

What were the plugs you pulled out like? wet, oily, carbonated or anything like that?

Its V5/6 so phase 2 yellow on sti and non.

Jap ecu has 2 wires to swap.

Black plugs points to rich. What reg is it running?

[vr4ex]

So the update today is that im now thinking that its spark related in relation to rpm., boost or no boost still seems to do it.

Crank gear or LH inlet cam gear giving sensor incorrect reading? Thoughts?

[Marky]

That makes sense

RPM related narrows it down a lot - if it was load / boost related that\'s a bit more vague as to causes

[Subirex Automotive]

 vr4ex said:

Got hold of the car with heating issues. Have got that sorted but cant get to run sweet. It looks like the motor has never been out or apart. Has got yellow injectors And have most likely never been out. Have checked fuel flow and pressure with 15lb of pressure on pressure reg. Ill rip injectors out tomorrow and check or swap. Havnt got access to graphing meter.

correct me if im wrong, but shouldn\'t the fuel pressure be around 35 to 43.5psi on idle?

[Kiwi_Fozze]

title changed to fixed, could you please enlighten us as to what fixed it?

[Guest]

 subirex']

[quote name='vr4ex said:

Got hold of the car with heating issues. Have got that sorted but cant get to run sweet. It looks like the motor has never been out or apart. Has got yellow injectors And have most likely never been out. Have checked fuel flow and pressure with 15lb of pressure on pressure reg. Ill rip injectors out tomorrow and check or swap. Havnt got access to graphing meter.

/quote]

correct me if im wrong, but shouldn\'t the fuel pressure be around 35 to 43.5psi on idle?

43.5psi with vac line off what I heard/run.