How To Test Engine Compression (1993-2008 1.8L Toyota Corolla)

Testing the engine compression of your Toyota 1.8L equipped vehicle is a pretty easy and simple affair, since the spark plugs are right on top of the engine.

In this tutorial, I'll walk you through the entire process in a step-by-step fashion and help you interpret your compression test results.

You can find this tutorial in Spanish here: Cómo Probar La Compresión Del Motor (1.8L Toyota Corolla) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles:

• 1.8L Toyota Celica: 2000, 2001, 2002, 2003, 2004, 2005.
• 1.8L Toyota Corolla: 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008.
• 1.8L Toyota Matrix: 2003, 2004, 2005, 2006, 2007, 2008.
• 1.8L Toyota MR2 Spyder: 2000, 2001, 2002, 2003, 2004, 2005.
• 1.8L Chevrolet Prizm: 1998, 1999, 2000, 2001, 2002.
• 1.8L Geo Prizm: 1993, 1994, 1995, 1996, 1997.
• 1.8L Pontiac Vibe: 2003, 2004, 2005, 2006, 2007, 2008.

CYLINDER MISFIRE DIAGNOSTICS:

• Misfire Codes: How To Troubleshoot And Repair Them (1996-2008 1.8L Toyota Corolla).

ENGINE NO-START DIAGNOSTICS:

• How To Troubleshoot An Engine No-Start Problem (1993-1997 1.8L Toyota Corolla).

Symptoms Of Low Or No Engine Compression

Depending on the compression problem or problems your Toyota is having, the two most common symptoms your Toyota will experience will either be a rough idle (misfire) condition or a cranks but does not start condition.

Engine compression problems usually fall into specific categories:

1. Uneven compression across all four cylinders.
2. No compression in all four cylinders.

I'll go into some detail about these two in the next couple of paragraphs.

Uneven compression across all four cylinders is usually caused by one or two cylinders that have low compression.

The end result of this low compression, in one or two cylinders, is a misfire condition that will cause your engine to miss at idle.

Here are some more specific symptoms you'll see:

1. Misfire codes:
   • P0300: Random Cylinder Misfire.
   • P0301: Cylinder #1 Misfire.
   • P0302: Cylinder #2 Misfire.
   • P0303: Cylinder #3 Misfire.
   • P0304: Cylinder #4 Misfire.
2. Rough idle.
3. Lack of power.
4. Blue smoke coming out of the tailpipe at idle and/or when accelerating (this is engine oil burning in the cylinders).

No Compression in all 4 cylinders and your Toyota won't start. It'll crank but not start. This usually indicates that your Toyota's engine is blown.

When you have a situation where you have no compression on ALL 4 cylinders, you'll see:

1. The engine cranks very fast and this fast cranking speed is very noticeable.
2. The ignition system is sparking all 4 spark plugs, so you know it's not an ignition system problem/issue.
3. The fuel injectors spray fuel.
   • You can confirm this with a Noid light test.
   • Also, you can confirm this, although indirectly, by removing the spark plugs and checking to see if they are fuel soaked (fuel fouled).
4. Fuel pump is working and providing pressure.
5. The most common causes of this scenario, are:
   • Blown head gasket.
   • Broken timing chain.
   • Engine threw a rod.

OK, having covered the most common scenarios of low compression and no compression, let's get testing to see if this is the case on your 1.8L Toyota.

Which Compression Tester Should I Buy?

There are lot of engine compression testers to choose from and many places to buy them. I'm gonna' make some recommendations to you:

TEST 1: The 'Dry' Engine Compression Test

If you don't have an engine compression tester, you can buy one from your local auto-parts store or, if you have an AutoZone or O'Reilly Auto Parts store nearby, you can rent one from them (they'll rent it for free, after you leave them a cash deposit for the tool, which you'll get back once you return it).

If you need help deciding where to buy one or which one to buy, take a look at my recommendations: Which Compression Tester Should I Buy?

IMPORTANT: You'll be working around a cranking engine, so you have to be careful and stay alert at all times. Think safety all of the time!

This is what you'll need to do:

1. 1

   Disconnect all of the fuel injectors. This will prevent fuel from being injected into the cylinders as you crank the engine.

2. 2

   Disable the ignition system:
   
   Distributor equipped → Disconnect the distributor connector(s).
   
   Ignition coil pack equipped → Disconnect both ignition coils from their connectors.
   
   COP ignition coil equipped → Disconnect all four ignition coils from the connectors.

3. 3

   Remove the COP ignition coils or spark plug wires.
   
   NOTE: If your vehicle has spark plug wires, label them before unplugging them from their spark plugs.

4. 4

   Remove all four spark plugs.
   
   As you're taking them out, be careful and don't drop any of them on the floor, or you could cause the spark plug's ceramic insulator to break, and this will cause a misfire!

5. 5

   Thread the engine compression gauge into the spark plug hole for the number 1 engine cylinder (this is the spark plug hole closest to the drive belt).
   
   NOTE: Hand tighten the compression gauge only! Do not use any type of tool to get it tight.

6. 6

   Have a helper crank the engine, when the test is set up, as you observe the needle on the compression tester's gauge. Once the needle on the gauge stops climbing, have him or her stop cranking the engine.
   
   Record this compression reading on a piece of paper. Include the number of the cylinder this reading belongs to. Now repeat steps 1 thru' 6 on the other 3 cylinders.

7. 7

   Write down the compression test result and the cylinder the test result belongs to.

8. 8

   Repeat steps 5 thru 7 on the next 3 cylinders.

Let's examine your test results:

CASE 1: Low or no compression in 2 or ALL cylinders. This isn't good and indicates that your Toyota has serious engine mechanical problems.

The most common issues would be:

• Blown head gasket.
  • To further test this, I recommend the following tutorial: How To Test For A Blown Head Gasket (1993-2008 1.8L Toyota Corolla).
• Broken timing chain.
• Engine threw a rod.

CASE 2: Low or no compression in one or two cylinders. This could be normal or it could be causing a problem.

To find out if the compression values are normal or not, go to: : Interpreting The Results Of The Engine Compression Test.

Interpreting The Results Of The Engine Compression Test

It's not unusual to see the cylinder compression readings vary between each other, especially in high mileage engines. Up to a certain point, this is normal, since the cylinders can wear unevenly across the engine's life.

If the compression readings vary too much, typically 15% or more, then the engine will suffer engine performance problems.

You can find out if the compression values you got are causing a problem one of two ways: You can calculate this 15% difference with pen and paper or you can use my low compression calculator. You can find the low compression calculator here: Online Low Engine Compression Calculator (at: easyautodiagnostics.com).

If you want to manually calculate the 15% difference, here's what you'll need to do:

• STEP 1: Multiply the highest compression value by 0.15 (this is the decimal value of 15%).
• STEP 2: Round the result to the nearest one (for example: 25.6 would become 26).
• STEP 3: Subtract the result (the number that was rounded) from the highest compression value.
• ANSWER: The result of this subtraction is the lowest possible compression value any cylinder can have.

Now, let me give you a more specific example: Let's say that the vehicle I tested produced the following compression readings:

Cylinder	Pressure
#1	165 PSI
#2	95 PSI
#3	155 PSI
#4	175 PSI

My next step is to do the following calculation:

• STEP 1:  175 x 0.15 = 26.25.
• STEP 2:  26.25 = 26 (rounded to nearest one).
• STEP 3:  175 - 26 = 149.
• ANSWER:  149 PSI. Any cylinder with this compression (or lower) value will misfire.

Since cylinder #2 is only producing 95 PSI, I can now conclude that it's 'dead' and causing a misfire.

To find out if the lowest compression value you got from your engine compression test is within a good range, you'll need to do the same calculation. Of course, you'll need to use the highest compression value you got and not the one in the example.

Once you've found the 'dead' cylinder, the next step is to find out what's causing the low compression value. For this step, go to: TEST 2: 'Wet' Engine Compression Test.

TEST 2: 'Wet' Engine Compression Test

To find out if the problem is coming from the top end (intake or exhaust valves) or the bottom end (piston rings), we need to do a wet compression test.

All that we're gonna' do is add about two tablespoons of oil to the engine cylinder that showed a low compression reading in the 'dry' compression test.

The engine oil will help determine if the low cylinder pressure or pressures you recorded in the 'dry' compression test are caused by worn piston rings or worn cylinder head valves.

Here are the steps:

1. 1

   Add a small amount of engine oil to the cylinder that reported low compression or no compression in the 'dry' compression test.
   
   The amount should be about 1 to 2 tablespoons of oil.

2. 2

   Install the compression tester onto the cylinder.
   
   Do not use any type of tool to tightened the compression tester. Hand tight is fine.

3. 3

   Crank the engine until the needle on the gauge stops climbing.

4. 4

   You'll get one of two results: The compression value will go up (from the one you recorded before) or it will stay the same.

Let's take a look at what your test results mean:

CASE 1: The compression value shot up. This tells you that the piston compression rings are worn out and thus the problem is in the bottom end (block) of the engine in your 1.8L Toyota.

CASE 2: The compression value stayed the same. This confirms that the problem is in the cylinder head valves.

More 1.8L Toyota Corolla Test Tutorials

There are several more 'how to' tutorials that I've written that are 1.8L Toyota specific, that may be of further help. You can find the ones that are located here in this index:

• 1.8L Toyota Corolla Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• How To Test For A Blown Head Gasket (1993-2008 1.8L Toyota Corolla).
• Misfire Codes: How To Troubleshoot And Repair Them (1996-2008 1.8L Toyota Corolla).
• How To Test The Ignition COP Coils (1998-2008 1.8L Toyota Corolla).
• Diagnosing A Toyota Corolla Misfire Case Study.