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Discussion summary
YOUR RESEARCH1999 C2 engine shaking.
Leading reported evidence
Install mounts, oem
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Boy I really hate to be the contrarian but when I installed my new mounts, OEM to OEM, I noticed quite a bit less vibration.
Leading evidence: 'Install mounts, oem' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check engine codes or aynthing' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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I replaced my sagging OEM motor mounts with OEM new motor mounts.
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Back in the day I used the water glass to tune Carburetors for smoothness, fuel injection "lean burn" systems are too rough for such delicate tests..
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Suggestion
That being said, I would follow the advice above and check newly installed parts first.
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been trying to chase down this. the engine just vibrates quite a bit through the cabin. more than it use to. things i have done to try fix this issue. car has 133k miles on it and other than idle shaking it really does run excellent. no check engine codes or aynthing
- new motor mounts
- new plugs
- new maf.
- new coils
any tips would be much appreciated. thank you.
When I put in new motor mounts I noticed a bit more vibration, probably because the new mounts are doing a better job of holding the engine steady.
You might also check the transmission mount if you haven't done so.
Boy I really hate to be the contrarian but when I installed my new mounts, OEM to OEM, I noticed quite a bit less vibration. In fact, I remember being quite excited that all of my audible rattles disappeared afterward. I'm talking rattles with the car in motion - there were none at idle beyond vibration to the point I could see the passenger seat shaking. Did you install semi-solid mounts by chance?
My passenger seat was shaking at idle. I replaced my sagging OEM motor mounts with OEM new motor mounts. Now smooth as butter. I am wondering if someone installed the motor mounts incorrectly. It can be done wrong. Have you ever opened your engine lid and looked in there?
Yea make sure the mounts r seated properly. There was a thread a while ago where the guy didnt correctly seat the mount/bolts and the motor looked crooked and it felt rough.
Since I put Rennline engine mounts on my C4S, it buzzes a lot, at certain rpms. I wonder if mine is not installed correctly. (I did install). The nut that locks center stud to mount (bearing nut?) can’t be torqued correctly as it needs to be moveable to fit into the square hole. If slightly off, will not fit correctly. Not an issue on OEM, as it is fixed position.
Take a video with a small glass on water sitting in various places, like roof, dash, floor board , console , steering wheel ect. to give a visual of the worst roughness.
That's probably me... OP check that the square hole has a square peg in it ... If your motor mounts causing the vibration it's pretty obvious to see if they're installed poorly (my case). I did not lift my engine high enough when securing the mounts I was overly cautious about putting weight on the block. excessive vibration is not normal.
https://rennlist.com/forums/996-foru...placement.html
awesome great ideas. thanks all. i am taking my car in on monday i will have my mechanic double check that. he is a porsche tech and i would imagine he did them right but you never know.
Ya ! Back in the day I used the water glass to tune Carburetors for smoothness, fuel injection "lean burn" systems are too rough for such delicate tests..
I would guess old injectors. Or a vacuum leak.
People always think it�s plugs and coils, but those items rarely fixed issues unless they are quite bad (plugs) or cracked (and get wet). I have yet to see fouled plugs posted here at Rennlist that wasn�t caused by some other issue that was causing it.
Lately I have been thinking about injectors on these cars. Especially '99 models, as some of these cars are almost 23 years old. I know mine were shot and there was evidence of this inside my engine from it running lean, which can result in a rough idle.
That being said, I would follow the advice above and check newly installed parts first.
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