Misfires and rough idle

MARIUS FERREIRA

MEMBER
2007 CHEVROLET CAPTIVA
2.4L
4 CYL
2WD
MANUAL
131,000 MILES

The idler pulleys came loose because of mechanic bad workmanship. Replaced everything Idlers new bolts everywhere. Replaced cam belt tensioner and cam belt, lined up all timing marks on bottom of crank and at the top of the camshaft pulleys. Car starts but backfires when pedal depressed to ref when hot engine sounds okay on revs but rough idle.

4 Replies

KASEKENNY

MECHANIC
18,907 POSTS

Based on what happened, I suspect the issue is with the timing. Even though you lined up the marks, they have to be in a specific location in order to be timed properly.

However, here are some other things this could be that you need to be aware of so let's review these:

https://www.2carpros.com/articles/engine-backfires-while-running

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

However the process is below for setting up the timing so I think we need to review this and then inspect the timing again just to make sure it is installed correctly.

Please let me know if you have questions. Thanks

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Sunday, June 27th, 2021 AT 9:00 AM

MARIUS FERREIRA

MEMBER
3 POSTS

Hi KASEKENNY1

Thanks for reply. Just to let you know this is the Z24SED motor it has a timing belt and not a timing chain. Will this procedure and marks still work the same for this motor or not?

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Sunday, June 27th, 2021 AT 9:55 AM

KASEKENNY

MECHANIC
18,907 POSTS

That does make a difference and going to make this harder as we don't have a manual on that engine. Is this vehicle in the USA or international?

However, the fact that this backfires and runs rough sounds like a timing issue.

Let's do two things. First we need to do a compression check.

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

Next we need to hook up a vacuum gauge and see what the gauge is doing when you are idling the engine. See the chart below for possible issues.

Thanks

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