Piston five misfiring

MARY RYAN

MEMBER
2004 LEXUS ES 330
6 CYL
4WD
AUTOMATIC
168,000 MILES

First mechanic said piston five misfiring, swapped coils, compression showed low all injectors- suggested replace all fuel injectors.
Dealer changed spark plugs, switched coils, fuel injector service - lowered misfire considerably. Next day lights on again. Second compression showed cylinder five at 143 PSI and all others w/in specs between 210 and 204 PSI per cylinder. Max compression 218 PSI, minimal at 145 PSI- recommended new engine.
She is in great shape otherwise- body and interior awesome. But don't think $4,000.00 worth age/mileage?
Currently runs okay, no problems starting/stalling/smoke. So question findings? Thoughts?

3 Replies

JACOBANDNICKOLAS

MECHANIC
108,289 POSTS

Welcome to 2CarPros.

The first thing we need to determine is why compression is low in that cylinder. It's odd that the others are fine. What I need you to do is check compression both dry and wet. Here are the directions. Note: Toward the end of the directions, is indicates if the compression is low in one or more of the cylinders, perform a wet test. Follow the simple directions listed and see what happens.

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First, here are a couple links that you may find helpful:

https://www.2carpros.com/articles/symptoms-of-low-compression

https://www.2carpros.com/articles/the-reasons-for-low-compression

https://www.2carpros.com/articles/how-to-test-engine-compression

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Here are the directions specific to your vehicle for testing:

2004 Lexus ES 330 V6-3.3L (3MZ-FE)
Component Tests and General Diagnostics

INSPECT COMPRESSION
a. Warm up and stop the engine.
b. Remove the intake air surge tank.
c. Disconnect the injector connectors.
d. Remove the ignition coils.
e. Remove the spark plugs.

See Picture 1

f. Inspect the cylinder compression pressure.
1. Insert a compression gauge into the spark plug hole.
SST 09992-00500
2. Fully open the throttle.
3. While cranking the engine, measure the compression pressure.
Compression pressure: 1.5 MPa (15.3 kgf/cm2, 218 psi)
Minimum pressure: 1.0 MPa (10.2 kgf/cm2, 145 psi)
Difference between each cylinder: 100 kPa (1.0 kgf/cm2, 15 psi)

NOTICE:
Always use a fully-charged battery to obtain engine speed of 250 rpm or more.
Check the other cylinder's compression pressure in the same way.
This measurement must be done as quickly as possible.

4. If the cylinder compression is low, pour a small amount of engine oil into the cylinder through the spark plug hole, then inspect again.

HINT:
If adding oil increases the compression, the piston rings and/or cylinder bore may be worn or damaged.
If pressure stays low, the valve may be sticking or seated improperly, or there may be leakage past the gasket.
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Now, if compression doesn't change when you perform a wet test, then either there is a valve issue or a head gasket issue. At that point, you would need to remove the head and inspect. However, if that is the case, the repair should be much less than $4,000.00. If the compression increases substantially, then either rings are bad or for some reason, there is excessive wear in that cylinder. At that point, it would be cheaper to replace the engine.

No one knows you car better than you. If it is in great shape, it may be worth fixing. What I always tell my customers is this. What can you get for the repair cost of this vehicle. Then they decide if it is a good choice to replace the vehicle or repair. Anymore, $4,000.00 doesn't get you much. The only real concern is what may go next. It does have a lot of miles on it.

Check out the book value online to see what it is actually worth. That may help you decide.

Let me know if you have other questions or need anything.

Take care,
Joe

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