Weird noise from engine when downshifting

[jkrustchinsky]

1987 944 n/a. Can anybody help with this, when down shifting and getting to about 4000rpms there is a weird noise thats tough to explain. best i can explain is (errnt). It happens quickly and goes away. If i rev the engine to about 4000rpms and left off quickly, it makes the same very brief ( errnt ) noise. Any ideas before i start pulling things apart. Josh

[TibetanT]

Josh, is the noise coming from the rear of the car?

[shinrai]

Heat shield? Exhaust related? check it out....

[John_AZ]

Josh,

If it happens while both downshifting AND reving to 4000rpm it could be as simple as a heat sheild as mentioned. Usually by the exhaust manifold. In a recent post, somewhere on the exhaust a crimp from the muffler or cat was loose. I have "body" noise on my "87 924S and cannot find it.

Does the sound appear to come from the top or bottom of the engine? I know this is next to impossible while driving but you may be able to duplicate the sound while under the hood.

Here is a link to a few noises and inspection:
http://forums.rennlist.com/rennforums/924-931-944-951-968-forum/350563-knocking-from-cam-tower.html

And this one is a suggested repair-"replace the front cam bolt" from mattdavis11.
Good pictures on this link:
http://forums.rennlist.com/rennforums/2854326-post1.html

GL
John_AZ