Car Went Bang!

[Mr_G]

Hey guys,

Just came back from driving and i was putting the car through its paces on a few nice stretches of road. I loaded it up one more time just before I reached destination and BANG! Mind you, car was revving @ 6.7kRPM and DID NOT hit the limiter. Car runs 14psi, with a 2540 turbo, pfc, injectors and all the supporting mods including a Q45 Afm which the car has been tuned for.

Ok, so I thought it would be the typical intercooler hose as it went "BANG", but I went over all the hoses and they seem to be fine. (Will pull off every single one and replace them during daylight.

Now, i was pretty upset knowing that its going to be something in the bottom end, expecting the worse to come about. But upon doing a compression test, each cylinder fired equally in pressure, with only 1psi variation in cylinder 3, compared to all 4 (SR20DET). All the plugs seems fine, ie none were coated in oil.

Now here is the problems & symptoms Im experiencing:

1) Car idles but sounds like a wrx and is abit rough on idle

2) Under throttle, car will only sound like a louder wrx and still have no power

3) BIG BIG loss in power as i cant get acceleration on, as it will only harm the car

If I could get any sought of advice, it would be most appreciative.

Jason

Edited December 2, 2006 by Mr_G

[Taso84]

is it blowing any smoke? and if so what coulour?

[Race_Bred]

your symptoms sound like you have a miss fire,

have you checked spark on all cylinders?

[MANWHOR3]

Maybe the turbo has blown? are you getting tonnes of smoke out the back?

[SECURITY]

your symptoms sound like you have a miss fire,

have you checked spark on all cylinders?

yeah sounds to me like its a problem with spark/ignition.

the bang could be from the loads of unburnt fuel in your exhaust hitting your cat or something (backfire).

so look at things like plugs, coils, cas, etc.

[BHDave]

Sounds like it dropped a channel on the ignitor. I'm yet to see a coil just stop working completely (unless the wiring was chopped somehow).

Find out which cylinder isn't firing, swap coils between that one and a working one. If the miss stays on the same channel it's likely the ignitor, if it moves to where the coil was moved to it's a coil.

When you did your compression test, what did the plugs look like?

[Mr_G]

Geeez, thanks for the quick replies guys.

Basically the car was under load (I was giving it throttle) and then a loud bang came from the car, then it lost response.

When the plugs were out, the 2 last plugs were slightly darker than the rest, but no oil was on the plugs. Ie the plugs appeard to have more blackness to them, rather than the front 2, which showed to be dark.

It was pretty dark, but didnt notice any smoke. Turbo is fine, as I could still hear it wind down as I shut off the car.

Compression was identical across all 4 cylinders.

SECURITY: Pretty sure the bang wasnt from the unburnt fuel. It felt as if I hit a rev limiter when the car lost power. Was close to the limiter, but still didnt hit the rev limit.

Edited December 1, 2006 by Mr_G

[SECURITY]

id still say it had to do with your ignition. look into it.

see if you're getting spark, pull your spark plugs and coil packs out, put the spark plugs into the coil pack as if they were in the car, hold it close to your motor so the spark can reach metal (to earth itself) and watch out for the spark while someone cranks your motor.

do that to all of them, for the ones that arent firing swap the coil pack over with one that is firing. that will help you figure out if its a coil pack/spark plug or not.

[Mr_G]

Just tested the coil packs. Its coil pack number 3. However I swapped 1 with 3, and its still on cylinder 3 with the problem.

The problem appears to be something with cylidner 3, not sure what tho, but there was no difference when i pulled out #3 compared to the rest.

Jason

[Rolls]

Injector?

[HRthirtyone]

so next you get a new plug for number 3.

if there is no change, look to the ignitor.

[WazR32GTSt]

well if coil pack 3 showed no spark then that's your problem

if the coil pack itself is ok, then check the loom to that coil, then try changing the ignitor..

it would take 5 seconds to swap an ignitor over...

[Mr_G]

Ok,

Just did some testing. All coil packs and leads fire properly.

Changed the plug, didnt do much but was slightly smoother than the old plug, but car still running on 3 cylinders and removing the coil pack on idle, cylinder 3 doesnt change.

So coil packs are now eliminated. Compression test pulled up fine.

What could it be? Injector?

The plug that was pulled out of cylinder 3 smelt like fuel if that helps

[Mr_G]

Actually, a guy on another forum reckons it could be a broken rocker arm, which is a common sypmtom to high reving SR20's.

Would a broken rocker arm cause the car to run on 3cyl?

Appreciate all the input guys

[BHDave]

If the rocker arms broke wouldn't that mean no valve opening and so no fuel getting in? So no fuel smell?

Check the ignitor!

Or pull the cover off the top of the engine and check for busted rockers. I'm yet to see a busted one in anything but a very big cammed very high reving engine.

If you have snapped a rocker and don't have rocker arm stoppers expect a very big mess when you remove the cover and an expensive repair.

[Mr_G]

Here is the problem, BIG THANKS TO MEATWAGON (Ns.com) + All others who posted on this thread, appreciate the help! Here is the mess!

At least the bottom end didnt let go! This was off the exhaust side on cylinder 3

It did some scoring to the outer part of that cylinder tho, please view pics and give opinons on weather this will harm the motor?

Edited December 2, 2006 by Mr_G

[SteveL]

Guaranteed to be a fatigue failure of the rocker arm. The question becomes, are any of the others cracked ??. NDI would tell the story, but might be worth changing regardless if this is a weak point.

Seems to be some scoring of the inlet lobe. Why does the inlet cam appear 'black' compared to the exhaust (lighting ??).

[Mr_G]

Guaranteed to be a fatigue failure of the rocker arm. The question becomes, are any of the others cracked ??. NDI would tell the story, but might be worth changing regardless if this is a weak point.

Seems to be some scoring of the inlet lobe. Why does the inlet cam appear 'black' compared to the exhaust (lighting ??).

Not the lighting, I bought the car not too long ago and this was the first time I basically pulled the rocker cover off.

I would really like to get it all cleaned up, and replace the valve springs, all the rockers and possibly get a set of cams put in at the same time.

Is this the shought of job that can be done in the home garage, or is it left to some sought of specialist?

[Sumo]

Depends, I dont have a great deal of expirience when it comes to the more indepth mechanical jobs, but new cams and tensioning it properly, re-timing it to run to get you down to the tuning workshop has to require a bit of knowledge.

Cheers

Sumo