blowby rings or ?

[jkloppi]

1995 Tacoma 4 cyl. Engine running blowby at oil fill cap. Checked compression around 120 each. Is this low. Any Ideas. 84000 miles just Bought it for the kid. Any info will help.Thanks Joe

[Brian R.]

Did you follow this procedure (particularly getting the engine to operating temperature and getting at least 250 rpm)? If not, repeat and report the results.

1. WARM UP ENGINE TO OPERATING TEMPERATURE

2. REMOVE SPARK PLUGS
3. DISCONNECT DISTRIBUTOR CONNECTOR
4. DISCONNECT COLD START INJECTOR CONNEC–
TOR
5. MEASURE CYLINDER COMPRESSION PRESSURE

(a) Insert a compression gauge into the spark plug hole.
(b) Fully open the throttle.
(c) While cranking the engine with the starter motor,
measure the compression pressure.

NOTICE: This test must be done for as short a time as

possible to avoid overheating of the catalytic converter.

HINT: A fully charged battery must be used to obtain
at least 250 rpm.
(d) Repeat steps
(a) through
(c) for each cylinder.

Compression pressure:

1,177 kPa (12.0 kgf/cm

2, 171 psi)
Minimum pressure:
981 kPa (10.0 kgf/cm2, 142 psi)
Difference between each cylinder:
98 kPa (1.0 kgf/cm2, 14 psi) or less

(e) If cylinder compression in one or more cylinders is
low, pour a small amount of engine oil into the cylin–
der through the spark plug hole and repeat steps (a)
through
(c) for the low compression cylinder.

•

If adding oil helps the compression, chances are
that the piston rings and /or cylinder bore are
worn or damaged.

•

If pressure stays low, a valve may be sticking or
seating improperly, or there may be leakage past
the gasket.

6. CONNECT COLD START INJECTOR CONNECTOR

7. CONNECT DISTRIBUTOR CONNECTOR
8. INSTALL SPARK PLUGS
Torque: 18N–m (180 kgf–cm, 13ft–Ibf)

[jkloppi]

I would like to know wear the cold start injector connection is. Then I will recheck commpresion the correct way. Eng does not seem to smoke at all. Would you have any other Ideas or things I can check that may be causing the psi at the oil fill cap. Thanks Joe

[Brian R.]

The cold-start injector is in the middle driver side of the air intake chamber. The connector is attached to it.

A plugged PCV valve or hose to it would cause some pressure in the engine. If you don't know how old it is, replace your PCV valve and check to see if you have vacuum on the hose attached to it when the engine is running.

[jkloppi]

checked compression the correct way all cly withen 5lb 0f 160. pvc valve is ok. Could I have bad valve seals or would this have shown up on comp. test. what is a telltale sign for head gasket eng. runs smooth,plugs look good no bad exhaust. No back psi on dipstik only at valve cover fill cap. Thanks Joe

[Brian R.]

Before we get too carried away here...

What makes you think what you're feeling is abnormal? Pressure is not that ridiculous. What about flow? Is there a large volume of air coming out the valve covers? or just a little and you feel pressure when you cover the oil filler cap hole with your hand? We're talking about an 11-year old engine. It will have some blow-by.

As a suggestion, get a bottle of AutoRX http://www.auto-rx.com/ and add it to your oil and run that for 1500 miles. Drain it after this time and fill with some cheap oil to flush the system. Run the flush for 2000 miles and drain. Replace with your normal oil and see if this helps. This stuff can have a real effect on getting rid of carbon/sludge in your rings and free them up if they are not beyond hope. From your compression, your rings are not too bad.

I have used it and it makes a difference if your engine is really dirty. It is not a solvent, it is a lanolin-based dispersant. There has been alot of discussion on BITOG server about Auto RX. See the following link for some information:

http://theoildrop.server101.com/ubb/...c;f=5;t=003792

[jkloppi]

The blowbuy is more of a beat than a constent psi. It will actualy carry some oil with it when the cap is off.

[Brian R.]

Try what I've suggested, it's a cheap possible fix.

[Flash75]

I think you may be concerned about something that is normal. With four pistons going up and down you will get some pulsing and vacuum at the oil fill if the cap is removed. If everything is running well and the engine isn't blowing smoke, using oil or leaking coolant there is no problem. If you have ever accidently left an oil fill cap off after an oil change you will realize there is a lot of pumping and oil movement in the engine.

Clifton