AE86 4age engine not starts crank ok backfires to air intake
06-12-2018, 11:43 AM
Post: #11
AE86 4age engine not starts crank ok backfires to air intake
The first explanation that comes close to fitting the situation that you
describe, is that you have one cylinder that is leaking compression. For
example, a bent or burned exhaust valve, damaged piston/ring or leaking
head gasket. This would not make smoke out the exhaust.

If the leak is small it could lower the compression on that cylinder enough
to cause it not to fire at low rpm's. But at higher rpm there is not enough
time for the compression to drop so low, and the cylinder will fire. It will
not be as strong as the other three cylinders, and I would still expect that
there would be some vibration.

The second situation would be if oil or coolant was leaking into the
cylinder. Only this would usually make smoke out the exhaust, and you
would have noticed.

I think a compression test should be your next move. If there is a
compression leak enough to stop one cylinder from firing, it will be obvious
when you test.

Cheers... jondee86

The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.
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06-15-2018, 01:32 AM
Post: #12
AE86 4age engine not starts crank ok backfires to air intake
So i have done compression tests and it looks following:

dry test (psi):
1: 165
2: 165
3: 160
4: 165

wet test with little oil (psi):
1: 260
2: 265
3: 260
4: 265

I think if i will be cranking the engine more maybe even more pressure will be built. There was no pressure drop on any cylinder.
What should be my next thing to check i can't perform leak down test as i don't have the tool for it.
I am thinking of cleaning AFM, throttle body than move to cleaning all the injectors.

85' AE86 GT coupe lifetime project since 2005
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06-15-2018, 07:05 AM (This post was last modified: 06-15-2018 07:06 AM by jondee86.)
Post: #13
AE86 4age engine not starts crank ok backfires to air intake
That's a HUGE difference between the dry and wet figures !!! Do you
have some way of checking the gauge, or can you borrow another gauge
to confirm that the figures you obtained are correct ?

Have you checked the cam timing ? How many km on the engine ?

Cheers... jondee86

The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.
Find all posts by this user


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