Rough warm start, but revving it evens it out

DOUGLAS CRAWFORD

MEMBER
2008 SUZUKI XL7
3.6L
V6
AUTOMATIC
160,000 MILES

The car will start on a cold start and run perfectly fine. But, after driving it or running it for awhile and turning off the car, when it starts it runs pretty rough. If I rev it to about 1300 - 1500 RPM's it will return to running normal and stay that way until I turn it off and restart it again. What could cause this? The valve cover gaskets were replaced recently and I noticed a broken bolt on the side that has a hose running to the air intake. Could this be a vacuum leak from a valve cover seal?

4 Replies

KASEKENNY

MECHANIC
18,907 POSTS

Do you have a scan tool that can read o2 sensors?

This sounds like a mass air flow sensor issue but we need to find out when you restart it and it is running rough what the o2 sensors are reading to determine if it is rich or lean. This could be a sticking injector or a MAF issue where the PCM is over or under compensating for what it is seeing.

Let me know what the short term and long term fuel trims are when this is running rough and we can go from there. Thanks

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Sunday, March 1st, 2020 AT 4:22 PM

JACOBANDNICKOLAS

MECHANIC
108,427 POSTS

Hi,

A rough idle can be caused by a vacuum leak. If you can, upload a pic of the hose you are referring to so I can see it. Also, is the check engine light staying on when the engine is running?

Here is a link that shows how to find and repair vacuum leaks. You may want to check the hose in question.

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

_______________________

There are other things that can cause what you described. A leaky fuel injector or even an engine temp sensor. Do you ever notice black or grey smoke from the exhaust when this is happening?

Let me know.
Joe

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Sunday, March 1st, 2020 AT 4:26 PM

CRAWFORD EVONY

MEMBER
1 POST

It was the vacuum leak I believe. I was able to replace the broken bolt and now the car runs perfect every start warm or cold. Thank you for the assistance!

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Monday, March 2nd, 2020 AT 1:58 PM

KASEKENNY

MECHANIC
18,907 POSTS

That's great news. Glad Joe was correct on this one.

If you care to leave a review at the site below that would be great. Clearly not necessary but would be helpful to get the word out. Thanks again for the update.

https://www.sitejabber.com/reviews/2carpros.com

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Monday, March 2nd, 2020 AT 4:48 PM