Advise needed..... smoke at startup and some visible oil leakage


Asked by Aug 14, 2012 at 03:01 PM about the 2004 Mazda MAZDA6 4 Dr i Sedan

Question type: Maintenance & Repair

In the last couple of years we have had a lot of repair work done to my vehicle.  Most recently the throttle body unit was replaced and an oil leak was fixed (valve cover, I think).  The dealership replaced the throttle body not long after an independent shop fixed the oil leak.   We are noticing smoke at startup and some oil leakage. I think we are going through two quarts of oil per week.  My questions are - where else can the oil be leaking from?  Should the leak have been addressed/noticed while the throttle body was being replaced? Could this have been caused by the replacement of the throttle body?    Any help is greatly appreciated!    

7 Answers


A clogged PCV will increase the pressure in the engine forcing oil into the throttle body. If you take off the air hose to the throttle body is there oil residue? Do you notice any oil on the ground or wet spots in the engine bay? When did you replace the PCV? Did your your mechanic do a compression check on each cylinder.

7 of 7 people found this helpful.

Tom answer sounds about right. Mine had valve cover leaks and would smoke after running for a while at red lights. Had me wanting to pull my hair out. Replaced gaskets and valve guide seals but it still would leak and smoke. Clogged pcv was the issue. Replaced it and it's vacuum hose and all the leaks stopped along with the smoking. Was using over a quart of oil a week. Now it doesn't use any.

2 of 2 people found this helpful.

Tom, thank you for your input. After reading your post and doing a little research it sounds like the PCV may be the culprit. I don't think we've ever replaced the PCV. I had Mazda replace the throttle body unit this past Spring and had an independent shop fix an oil leak (valve cover gasket) right before that. My husband know a little about cars.... Can you give us step by step instructions on how to replace the PCV Valve and hose?

5 of 5 people found this helpful.

I have the same trouble with my 2004 Mazda 6. Smoke on startup. Oil residue in intake. Also had to replace valve cover gasket on front cover. Was getting oil on plugs # 5 & 6. Still smoking on startup. Replaced PCV . Trouble gone and stop using oil. Thanks for all the help. I have been fight this problem for 6 months. I have 177000 mile on it now. Thanks again for all the help. This is a must read if you are having this problem. Thanks , Jeff

5 of 5 people found this helpful.


Wow I'm surely amazed I've been working catching rides and pulled out all my hair on my head trying to figure out what's wrong with my car. It was running great until my friend added some engine cleaner into the oil and all he'll broke loose. My baby hasn't been the same . I changed the pcv valve cleaned the trottle body, egr. Plugs and coils 3 times. That's when my friend suggested to add the cleaner to the oil and my night mare became worse. Does anyone have any suggestions what should I do next . I know a little mechanics work but emissions control cars I'm still new at but willing to try anything at this point. I love my 03 mazda 6 3.0 . Please help me greatly appreciate any info

Having read above comments, I also confirmed to PCV valve, which can fix smoking issues. This is my recent experience.

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