QuestionMy 1991 Miata has an engine or valve rattle at about 2800-300 rpm. It sounds like valve rattling. Above or below that rpm no noise. It is evident in 1, 2, 3 gears, not sure in 4th or 5th. I have read a post referencing this problem with fairly simple remedies, but can't find it. I would like to take the information to my mechanic. I am a woman and do not work on cars myself, but I love my little Miata.
Help will be appreciated.
AnswerA common noise complaint is related to exhaust heat shields.
Heat shields are crimped and welded down the entire exhaust system. It is common for the attachment points to fail (crack/loosen) and allow the metals to vibrate at given RPM's. This vibration can translate into different noises that come and go. Further, catalytic converters can fail internally whereas parts of the substrate may break loose and be trapped in the casing. These can also create noises with RPM. A typical converter can see 125-135k of use, many here are still in service at almost 20 years.
Try not to suggest to your mechanic what the problem is rather let them blindly discover it. Suggesting a internal mechanical problem to an unscrupulous shop could afford them the ability to knock that one out of the park and empty your purse as a result.
As long as you;
Have always maintained reasonable oil changes
Used high grade oil and the correct weight
Used a Mazda or better oil filter
Not overheated the engine (maintained good coolant level)
Are under 250,000 miles
If you meet the above then I find it very unlikely that you have an internal engine related failure, especially valve or lifter. If you had an internal mechanical failure such as above the noises would worsen with time and be consistent.
If you monitor the issue and send more specifics I may be able to help further.
service@miatashop.com
