AE86 4age engine not starts crank ok backfires to air intake

[jondee86]

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

[Ryo]

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.

[jondee86]

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

[Ryo]

I will check the gauge if it is okay the cam timig was okay the engine is having 188tkm. I have finally found the issue it was in clogged fuel injectors using carb cleaner done the trick all is running smoothly as before maybe even better.So my AE86 is repaired. Thank you for all the valuable information.

Now i can return to original issues for that i opened this topic with my friend AE86 as it seems the trouble is still there and the engine have problems to run correctly. I will check the compression gauge and start from checking on his engine compression. Betting that there can be simillar problems like on mine as the car was not moving much last 3-4 years.

[Ryo]

We have done compression test on my friends AE86 4AGE and the compressions are good.
My concers now is why the engine is so hard to start with smaller capacity battery i need really fully charged good battery to start the car than starting a few seconds (mine starts after 3sec or so but mine friends i need to wait a while).
Once the engine starts i need to keep it on gas or the engine stalls. Also it feels like running on 3 cylinders as the car really shakes.
It is heard really noisy valves but when i keep it for a while in this condition and engine gets warmer it just start running on all 4 cylinders without helping it with hitting gas and the idle gets stable as well.
My only idea what this mean is that one piston is dragging on piston rings causing load on the whole engine.
I am thinking about properly flushing whole engine or using little petroleum in each cylinder if it makes a difference.
The engine was reuilded more than a 5 years ago but the car was not moving like 4 years and was parked outside. What i remember previous owner did replace pistons with rings without doing anything with the engine block so i bet there can be trouble.
Other things i noticed: Fuel pump was replaced pressure is minimal according the manual, fuel pulsation damper is missing screw above, all injectors sound is the same (have not cleaned them yet) When i service wire the fuel pump without starting the engine i feel sometimes touching the fuel line vibrations like the flow is not right. No idea if this can have so big impact as the pressure is according min specs and the fuel pressure is not dropping. Any ideas what i can do next?

[Nakilad]

Old fuel? Pulsating fuel line when bridged could be air in the line (i.e. split in the fuel pickup in the tank) or a blockage. Try dumping the fuel into a bucket when bridged to see what the flow is like.

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[Ryo]

I can try external fuel pump in canister if this helps but still i think i am fighting with two or three problems as i mentioned after longer cranking the engine it starts but like on 3 cylinders with really noisy lifters but will not hold idle i must keep it on gas after the engine gets warmer it starts an all 4 cylinders and it runs stable. No trouble to start the engine immediatelly when warm. Plugs are always wet from fuel. Also it sometimes fires into air intake when starting and i already see some dirt in air filter probably fuel (AFM still okay as i tested it in my AE86 last time). Now i don't know which way i should proceed as i think fuel delivery is still working but feels like something is clogged. And i remember i smell fuel as well in engine oil as oil level was above dipstick so i needed to drain it to normal level. Engine oil was all dark as well. Engine oil is Eneos 10W40 was changed only about 200km back when we tried to drive a car a little. The problems started after battery was changed for new one and engine oil changed. As i mentioned before car was not started for about 4 years and was parked outside in summer or winter. The fuel is not old as we drained the old one and put new inside already. Fuel filter was still not changed and injectors have been not cleaned yet i only inspected their sound with screwdriver. Was iaming to clean them but still not sure if mine problem is in fuel delivery as when engine is hot it runs well and i can rev it than without any issue.

[jondee86]

(08-14-2018 11:31 PM)Ryo Wrote:  We have done compression test on my friends AE86 4AGE and the
compressions are good.

What were the compression readings? And did you get that gauge
checked to make sure it was reading right?

Quote:My concers now is why the engine is so hard to start with smaller
capacity battery i need really fully charged good battery to start the
car than starting a few seconds (mine starts after 3sec or so but
mine friends i need to wait a while).

Have you checked the timing? Hard starting can be a lot of things...
cold start injector not working, AAV broken, (does it rev up to 1500-2000
rpm once it does start?), low compression etc.

Quote:Once the engine starts i need to keep it on gas or the engine stalls.
Also it feels like running on 3 cylinders as the car really shakes. It is heard
really noisy valves but when i keep it for a while in this condition and
engine gets warmer it just start running on all 4 cylinders without helping
it with hitting gas and the idle gets stable as well.

Sounds suspiciously like a leaking head gasket allowing coolant to leak
into one cylinder overnight. Does it start fine when the enine is warm?

Cheers... jondee86

[Bean]

I think you're on point with assuming several issues.

Jondee may very well be correct on the cold start part. I guess the valve underneath the throttle body (with the wax element) is stuck in closed position. This would at least make sense why you have to push the accelerator while cold but not once the engine is warm. This will also result in too mich fuel being injected or more accurately not enough air to burn the fuel injected.

Very dark oil after such a short period does point to a failed seal (headgasket or valve stem seals). This is a long shot but technically if you the stem seal failed sufficently exhaust and fuel may be pushed into the head and from there to the intake plenum.

If you can get hold of a leak tester (similar to a compression tester) you should get some more results (mind you a failed stem seal won't show there but exclude other points).

Best of luck.

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