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failure followed by black smoke..please help

4178 Views 15 Replies 7 Participants Last post by  spud majic
so to clear thing up i have many mods but also have the correct tune for the parts. moderate tune of 400hp with methanol on 93 octane with 22psi from a blouch DOM 4.0...

The last few days i had people behind me see black puffs of smoke when i let off the throttle at WOT. i baby this car extremely and i always let the oil heat up fully before i do anything fun and that usually takes about 10 minutes of driving. well this past friday i was driving for about 8 minutes and the oil was just about at the right temperature (like 85% of the way fully warmed up) and i decided to give it 3/4 throttle around a turn in 2nd then go to 5th. The AFR's were 11.0-11.1 which was normal but then at about 16-18psi when i let off the throttle to shift the engine shut down. so i held the clutch and started it again. it started but died right away. i decided i wanted to look at it before starting it again so i pushed it to a parking lot and when it was light i looked at everything. it all looked solid...nothing leaking or anything. i reset the ecu loaded the tune on again and started it. it started but would die right away, i started it again and could keep it alive with the throttle but only for 5 seconds. a few guys outside the car said they saw black smoke everytime i increased the throttle...

it doesnt idle....what could this be?

i pulled the turbo thinking it blew and the shaft got stuck sideways in the housing restricting the exhaust gas. The turbo isnt perfect but it spins fine. it has some play but i cant get it to touch the housing...close :/

so IMO that eliminates the turbo as the reason that its not running. When i kept it alive with the accelerator it sounded normal, didnt sound like one cylinder wasnt running or anything but my next step is to pull the plugs and inspect...maybe do a compression check...compression was 120 across the board in the spring and it was 120 when the engine was built in 2010.

any input would help thanks. and if your near Indiana i will supply very good food and possibly some good alcohol if you would lend a helping hand to a fellow Subaru owner.
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black smoke = too much fuel. something is causing the engine to either see more air than is actually going to the engine(failing maf sensor?), or something in the fuel system is failing (injector stuck open? fuel pressure reg not relieving pressure?)
which of those could break while driving? and i cleaned the maf last spring so ill check that. could it be the map sensor? how could i check it? and whats a good way to check for leaks in the intake system or how could i test an injector?
Im in indianapolis if you need a hand. I put this up on IIC (indiana impreza club). I know your not too active on that site yet but a lot of the locals would be willing to lend a hand for sure!
Unplug the MAF and see if it idles. If so, bad MAF. Could also explain why you get black smoke, if it's telling the ECU more air is flowing than is and it is running very rich.
thanks guys i will check these things.

Stiboost21, thank you for posting in the local site. i have an account there but have had problems being able to post so i havnt gone on there lately. Im located in terre haute, roughly an hour from indianapolis. it would be great if i could get a helping hand, i will provide food and drink as promised, there are a few other subaru owners here aswell, so it could be like a small get together. my number is 215-327-0055. thank you
^ My pleasure. LMK when you get your compression test results back.
so news....compression is 120 in 3 cylinders and 118 in the drivers side front. so thats good.
I noticed a whole in the front flex pipe on the up pipe. (picture attached) and the spark plugs are fouled. also while doing the compression check i had to hold the butterfly valve open by hand because the throttle did nothing. Im pretty sure this car is not drive by wire so that means that my throttle cable snapped or something along those lines. opinions?


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k so it is DBW....should it open only when the engine is running or just when the ecu has power and throttle is touched? i need to get the manual and see what the volts are supposed to be and check that i guess
fixed everything and the car runs fine now...besides the brakes that still need to be done

STIboost21...thanks for posting for me
Glad you got it fixed, but the real value of the thread is: what caused the black smoke/not starting problem, and what fixed it??? Thanks.
fixed everything and the car runs fine now...besides the brakes that still need to be done

STIboost21...thanks for posting for me

My pleasure. Glad everything worked out alright.
The problem was that the IC piping on the cold side came loose and under boost the plugs got fouled. Which wouldn't let the car run normally. Originally I thought it was the turbo seizing but that was not the case even though it does have a bit more shaft play now. The car idles well and revs up normally now. The current problem is that my oil pressure gauge reads 20 at idle and drops to zero when driving. Or visa versa. It's weird. So I'm not driving the car at the moment but I'm going to plug in a tester into the port to see what the pressure really is. The gauge in the car is an eBay gauge installed by the previous owner I don't trust it. I know the oil is circulating because when I pull the dip stick right after I shut off the car the oil is lower on it then before I started the car. So for anyone having a similar problem....check compression to verify that the engine is still healthy and as u do that u will also see ur plugs. No need to overestimate the damage like I did. I shouldn't have pulled the turbo out first but instead just did the compression test first.
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a reader will not tell you oil pressure. iirc the factory oil sensor is an on off switch.
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