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Misfire cylinder 4 ej207 (solved)


Hooch
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Hello

 

I have a 2008 sti grb. I have just rebuilt the engine. The engine originally had a misfire on cylinder 4, removed engine and stripped found broken ringland and a hole in number 2 & 4 pistons. Also exhaust valves were burnt on cylinder 4 so they were replaced with new valve seats and valve clearances made… also two 2nd hand pistons and new piston rings, bearings etc. (engine reconditioners put the heads together)

 

Any way put engine together and in, started up and there is misfire on idle cylinder 4… 

compression test: all cylinders around 80psi thought this was quite low..

timing good

has spark 

swapped coils and spark Plugs over 

In the process of swapping fuel injectors over but now needing two seals the orange ones on top of the injector cant my find these anywhere.. does anybody know where to buy these from? 
 

I doubt it’s a fuel injector problem but going through process of elimination. 

I’m thinking it has something to do with the head work done on that cylinder. Not keen to pull the engine out again 😅

 

Is there anything else I could check? Will

do a leak down test after finding a injector seal 
 

Does anybody know where I can get the orange injector seals from?

 

Thanks 

 

 

Edited by Hooch
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38 minutes ago, Hooch said:

Yeah true! 
 

Well cylinder 4 did have a broken coil connector plug that I’ve had to solder a new plug on. But the coil seems to be working 

 

oh you have coil on plug.. I always forget that... removes one possible source of a misfire.

 

Was the cause of the first engine failure ever diagnosed? Like was it detonating or running lean... and has that been fixed?

 

 

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On 15/08/2021 at 5:44 PM, Loren said:

 

oh you have coil on plug.. I always forget that... removes one possible source of a misfire.

 

Was the cause of the first engine failure ever diagnosed? Like was it detonating or running lean... and has that been fixed?

 

 


I bought the car with low compression off someone I knew. The car had a boost controller. And by the looks of the old pistons the boost was turned up way to much.

I’m pretty sure it’s running lean. There was no air filter or snorkel on the air box and a lot of oil in the turbo/intercooler. 
Can’t do any more test at the moment till lockdown is over ☹️ still need to swap injectors to cross that off the list.

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How do you know the misfire is on 4?

 

 

Do you think it's lean all the time or just on boost?

 

Lot's of oil in the intercooler is to be expected if you had a broken ring land as all the extra blow by goes straight back into the intake system.

 

 

 

 

 

 

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On 19/08/2021 at 2:28 PM, Loren said:

How do you know the misfire is on 4?

 

 

Do you think it's lean all the time or just on boost?

 

Lot's of oil in the intercooler is to be expected if you had a broken ring land as all the extra blow by goes straight back into the intake system.

 

 

 

 

 

 


Because the spark plug is fouled with fuel and when unplugging each coil the only cylinder that stays misfiring is #4

 

Misfire is at idle. Have only had it running for about 2minutes then switched off,  


Yeah true! 

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  • 3 weeks later...

Solved! 
 

Ecu was the problem. Carried out some scope tests on the ecu using my oscilloscope and wasn’t getting the correct reading.

 

Swapped one out with a second hand and drives like a dream. 

Edited by Hooch
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  • Hooch changed the title to Misfire cylinder 4 ej207 (solved)

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