Poor acceleration and high fuel consumption after repairing a misfiring cylinder

SAMBOHAMBONE

MEMBER
2000 HOLDEN RODEO
3.2L
V6
2WD
MANUAL
267,000 MILES

Hi, my vehicle listed above has a oil leak in one spark plug tube causing it to misfire for a few days. I cleaned the oil out of the tube and replaced all 6 spark plugs and it ran great for a day or two until it filled up with oil again. It misfired again for another day or two until I fixed the leaking gasket. Since then I noticed a noticeable drop in acceleration and fairly high fuel consumption. I was thinking it could of damaged the catalytic converter so I unbolted it a bit upstream and took it around the block. I didn’t notice any improvement in acceleration. Could the o2 sensor be causing the issue or the catalytic converter or something else? It feels like it’s being held back.

Thursday, October 24th, 2019 AT 2:14 AM

3 Replies

AL514

MECHANIC
5,499 POSTS

Hello thanks for using 2CarPros. How did the spark plug look when you took it out of the oil filled tube? Has the check engine light come on? An oxygen sensor stuck lean, low voltage. Will command the ECM full rich. Have the ECM scanned for codes and let us know. If you're concerned about an 02 problem here's a guide to testing it: articles/how-to-test-an-oxygen-sensor-02-sensor

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Thursday, October 24th, 2019 AT 5:48 AM

SAMBOHAMBONE

MEMBER
2 POSTS

The spark plug looked okay. There is no check engine light on. It idles fine and isn’t blowing smoke from the exhaust. Just seems like it’s being held back on acceleration.

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Thursday, October 24th, 2019 AT 10:58 AM

AL514

MECHANIC
5,499 POSTS

You should still have it scanned for codes, with the previous misfire there will be data saved. Next a fuel pressure test should be done to make sure it is within spec.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator.

Here is a guide for the catalytic converter test as well:

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter.
https://www.2carpros.com/articles/engine-has-low-power-output. https://www.2carpros.com/articles/symptoms-of-low-engine-power

There can be many possibilities of low power and high fuel consumption, with the high mileage you have already, a scan tool which can read live data should be used so fuel trim numbers and oxygen sensor information can be seen. But checking fuel pressure is where to start with this issue.

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Thursday, October 24th, 2019 AT 1:12 PM