Rough idle and loss of power?

MARIOC68

MEMBER
1995 TOYOTA COROLLA
287,500 MILES

Greetings. Difficult to start in the morning. Normal idle with engine still cold; but when it reaches its normal operating temperature the idle drops quite a bit and is very low and unstable. When I accelerate you can hear the engine knock.

Tuesday, May 9th, 2023 AT 7:04 PM

5 Replies

KEN L

MASTER CERTIFIED MECHANIC
47,643 POSTS

This can be because of a vacuum leak. I would use this guide when the engine is cold to confirm the leak:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

This guide may help as well:

https://www.2carpros.com/articles/stall-at-idle

Please go over these guides and get back to us.

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Wednesday, May 10th, 2023 AT 11:41 AM

MARIOC68

MEMBER
120 POSTS

Still having a low idle problem with a warm engine, but I'm getting some power back after repairing some vacuum leaks through the throttle body and a bad contact wire on the oxygen sensor. I also want to highlight that the valve gap was verified, finding a #4 cylinder intake valve with a gap greater than 0.25 mm, which is the maximum limit specified by the manufacturer, all the others and the exhaust valves are correct.

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Friday, May 19th, 2023 AT 4:45 PM

KEN L

MASTER CERTIFIED MECHANIC
47,643 POSTS

That is a good sign. I did find this guide we can go over as well. This shows you the top problems for no power.

https://www.2carpros.com/articles/engine-has-low-power-output

Please go over this guide and get back to us.

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Sunday, May 21st, 2023 AT 11:25 AM

MARIOC68

MEMBER
120 POSTS

Engine compression test: cylinder #1 192 PSI; cylinder #2 190 PSI; cylinder #3 187 PSI; cylinder #4 210 PSI.

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Wednesday, June 7th, 2023 AT 4:40 PM

KEN L

MASTER CERTIFIED MECHANIC
47,643 POSTS

So, the compression is good, have you changed out the fuel filter? I would also service the throttle body.

This guide can help walk you through the service:

https://www.2carpros.com/articles/throttle-actuator-service

Here is the fuel filter location so you can change it out. Check out the images (below). Please let us know what happens.

Images (Click to make bigger)