Compression test

[TROOPER88]

Hi Guys
I have thread running under the VW section but my query is more general engine specific.

I have a misfire and after replacing / checking the plugs, leads and coil, I have now removed the inlet manifold to allow me to gain access to the plug ports. The engine is a 2.0 and of shockingly bad design where the inlet manifold has to be removed (AZJ).

Is it ok to do a compression test with the manifold removed?

I have, and on all 4 cylinders I got the same reading; a high ish reading, just off the green 'ok' gauge on the tester. 16 bar on all 4.

Will the pressure been lower with the manifold on?

The engine was cold.

I just need clarification than my test and my results are good

If so, I can test the injectors next

Many thanks

[Boosted LS1]

I think you're fine. The engine thinks you were at wide open throttle (WOT) and you got good results. It may be a tad lower with the manifold attached but you'd still have had high readings.

[TROOPER88]

Thank you.

I could blank off the inlet ports and try again to see if I get much lower.

Are my readings too high??

Cheers

[Boosted LS1]

I think you can move onto checking other things.

[TROOPER88]

Boosted LS1 said:

I think you can move onto checking other things.

Thank you 😊

Fuel injectors next 👍🏿

[Steve_D]

Just to add...a compression test is measuring how much air is being compressed so blanking the inlet would leave it with no air to compress. this is why you always do comp. tests with the throttle open.

Steve

[TROOPER88]

Steve_D said:

Just to add...a compression test is measuring how much air is being compressed so blanking the inlet would leave it with no air to compress. this is why you always do comp. tests with the throttle open.

Steve

Yep, understood

Thanks Steve

[Mr2Mike]

TROOPER88 said:

Hi Guys
I have thread running under the VW section but my query is more general engine specific.

I have a misfire and after replacing / checking the plugs, leads and coil, I have now removed the inlet manifold to allow me to gain access to the plug ports. The engine is a 2.0 and of shockingly bad design where the inlet manifold has to be removed (AZJ).

You don't have to to remove the manifold to get to the plugs.

[TROOPER88]

Mr2Mike said:

You don't have to to remove the manifold to get to the plugs.

Hi Mr2Mike
Everyday is a school day...

This is the engine:



How would I get access to the plugs in cylinders 2 and 3 without removing the manifold?

Even if you could remove the plugs, how would I be able to screw in the compression tester without being able to see the plug hole?

Thanks for your input

[Mr2Mike]

TROOPER88 said:

Hi Mr2Mike
Everyday is a school day...

This is the engine:



How would I get access to the plugs in cylinders 2 and 3 without removing the manifold?

Even if you could remove the plugs, how would I be able to screw in the compression tester without being able to see the plug hole?

Thanks for your input

Same as the AQY and later engines. The inner two spark plugs are angled outwards so they can be reached with a spark plug socket and a universal joint. It's fiddly for sure, but doable. A proper compression tester that uses a flexible hose and screw fitting (rather than the toy ones with a rubber bung) should be able to be fitted.