Hi,
I’m looking for some help diagnosing the issue I have. I hear some sort of tapping/clicking noise from around the inlet manifold. Seems like the sound comes from in between the manifold and engine. I know that fuel injectors do make noise, but this one I started to hear about 3 months ago. It is most noticeable when the car is cold and on acceleration. When I start my car when it’s cold it stays at 1.5 RPMs which is normal and then goes to idle after some time. But, I when it is doing that I get some vibration/vibration sound when it hits 1000 RMP. Below or above 1000 RPM everything is fine. Lastly, when I approach a red light and put the car in neutral (I know I probably shouldn’t) car stays at 1000 RPMs until I stop and then lowers to idle RPMs.
I started noticing that after I change the fuel filter which caused some revs fluctuation issues.
Anyone had a similar problem or have any ideas?
I have got NB 2.5i Sport with VVT engine 1.8.
Leaking exhaust manifoldscan make a ticking noise.
Whether the same is true for an inlet manifold I don’t know but if it is a leak, you should be able to pinpoint it with a rubber or plastic tube. Stick one end in your ear and probe with the other end
Thanks for the reply @999to5
I managed to do some diagnostics today.
I checked a few places around the inlet manifold with a stethoscope. Nothing really stood out and all injectors sound normal. The car was warm so I could potentially miss something. I will try to do it when it’s cold and use a rubber tube as you suggested.
I also did a compression test (on a warm engine) and the results are about 135, 136, 130, 132 psi. They are all close to each other, but isn’t that too low overall? (This one I know its not really related but I did it just to check if everything is fine)
I will try to do an exhaust leak test over the weekend and also I could do a smoke test for the inlet manifold to check if it detects anything but would have to find a garage that has a smoke machine.
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Ok. It’s been a week or two. I checked for leaks in the exhaust manifold as much as I could without taking the heat shield out and there is no sign of any obvious leaks. I also made a simple smoking ‘machine’ and tested the inlet manifold with the same result: no apparent leaks.
Video: MX-5 engine noise - YouTube
I made a quick video of the engine running when it’s cold. I seem to notice some wired noise that I think wasn’t there before. Also, when I stop the engine there is some hissing air? noise somewhere from the inlet manifold area. Or maybe I’m going crazy. Anyone can hear anything out of ordinary? Unfortunately I can’t compare it to any other MX5.