2000 Turbo misfire/cutting out

[aaron_2000]

I'm currently trying to figure out what the issue is. I can let it idle all day and it will never misfire or cut out, but after about 20 seconds of driving it on boost, I get a 3 fast/3 slow CEL followed by a misfire that gets worse and worse. It had a severe boost leak due to an exhaust leak when I bought it, after fixing that by changing the up pipe gasket it still felt down on power, then just cut out entirely. I managed to get it running again by unplugging the MAF, it then went back to normal after I plugged it in. I'm guessing there's still a boost leak somewhere seeing as it's only when I bring it onto boost? There's no black smoke and the turbo itself seems smooth, it's just down on boost followed by the appalling misfire. It's a standard S reg V4

[aaron_2000]

R12many said:

So you've done a boost leak test or was the original leak so obvious you didn't need to?

The up pipe leak was very obvious, it runs quieter now although there's still a noticeable leak. It never outright cut out on me before the gasket change though which is odd

[aaron_2000]

R12many said:

Fix the leak first. Is the MAF a genuine Subaru one or a cheap one off Ebay? If it's the latter then get a genuine one. After that check plugs and if need be replace them. Get a leak down test done, ring land failure is less common on a 2.0 but the car is over 20 years old.

Good question regarding the MAF, plugs are all being checked in the morning along with a compression test. I think the issue is boost related which is screwing with it when the MAF is plugged in

[aaron_2000]

R12many said:

Yes, lot's of stories on the internet of cheap MAFs screwing up the fueling. Do the basics first as the fix is probably quite a simple one. EJ20 engines are pretty solid internally with regular oil changes but after 20 years everything around it will start to need attention. Good luck.

My first thought was MAF, but the garage diagnosed it as the very noticeable up pipe leak. Lost faith in them after I realised it was worse after they fixed the leak, so I'll likely take it to Richard Henry. My two thoughts were either bad MAF or a boost leak messing with the MAF. I'd guess MAF though, although it's not showing on diagnostic. Appreciate the help

[aaron_2000]

Since I bought it, if I left the MAF plugged in it would run worse and worse gradually before eventually cutting out. I could then unplug the MAF and it would drive in limp mode without ever cutting out, that's how I managed to drive it the 130 mile trip back with the MAF unplugged. Sign of a bad MAF then?

[aaron_2000]

R12many said:

Yes indeed. I think it's about £80 for a proper one.

Turns out the BCS test cables were plugged in. Unplugging them has made a massive improvement although I still think the MAF is bad, got a new purple label one on order

[aaron_2000]

R12many said:

Are you talking about the connectors near the steering column? If so then did you constantly have the fans and solenoids cycling?

Yeah, it seems to have rectified the issue. Still running a little lumpy which I have to look into

[aaron_2000]

vxr2010 said:

try a reset on it , if it’s had the connectors paired for that long it’s probably confused the ecu

How do I do the reset?