Why does a car shake when idling after sitting for years?

“When accelerating hard (over ~50% throttle) in the 15-25 mph range, there's a noise/shake that sounds like you're running over one of those rumble strips, that are placed before stop signs & persists until I ease up on the gas.”source ↗

“My only guess at this point, is a busted engine mount, or some kind of misfire that isn't showing up in obd2.”source ↗

“Any help would he a godsend!”source ↗

“My 2014 Honda Accord Sport has been shaking on and off when the AC is on and at idle.”source ↗

“It doesn't always happen either.”source ↗

“I also notice that with the AC off and sometimes putting the car into reverse it does almost the same type of vibration.”source ↗

“What else could be causing all this?”source ↗

“Is this a normal amount of vibrations while on park ? 2018 Nissan rogue, 93k. I can feel the vibrations while driving as well but bot as strong. Do i need new motor mounts or am i cooked?”source ↗

“hello, so my car (2016 ford fusion… 118,242 miles) will lose power and shake (feels like shuddering)…. the check engine light is solid and when it comes on my car just says “see manual”.”source ↗

“This van's (2004 Dodge Grand Caravan 3.8) has been sitting out for 3+ years and I'm considering getting it to a comfortable state to drive. It shakes the most in reverse, a little less in drive, and little less in park, and (I think) a normal amount in neutral.”source ↗

“i started it and i got engine fault limp mode, then after 1 more start it was gone and no limp mode.”source ↗

“hey there! it’s got no codes, and everything else is stock. not sure what a flex pipe is.”source ↗

“I topped it off about 2 weeks ago. But I’m pretty sure the radiator’s leaking a bit so I’ve got a new one ready to go. Not sure if that has sum to do with it.”source ↗

“Car runs fine cold/driving but once fully warm, the idle starts hunting and it stalls at stops.”source ↗

“Wouldn’t a stuck-advanced intake phaser show up as actual cam angle not matching commanded angle? Mine stays within about 1° even while the idle is hunting. Is there a mechanical way you’d recommend verifying the phaser/timing despite the scan data?”source ↗

“When the engine is warm and I come to a stop (e.g. at a red light), the engine starts shaking slightly after about 20 to 120 seconds of idling.”source ↗

“What exactly does roughness Point to? Is -50 already Bad? Is it only bad If all added do not add up to 0?”source ↗

“recently I've noticed that when I come to stop signs or red lights it seems that my idol is lower or seems to have a rough idle in drive..... I recently replaced spark plugs I replaced the blow by Valve and I tried to perform a smoke test to see if there were any vacuum leaks but I am unsure if I did it correctly..... Has anyone else had this issue and if so what have you done to correct it?”source ↗

“So my 95’ Honda Civic has been idling like this for a while now, and I’m not sure what the issue is?! It’ll also stall sometimes on idle, making that pulsing sound + vibrating.”source ↗

“recently my car started having issues where it would make this weird noise while idling or accelerating.”source ↗

“From a dead stop it will sometimes not respond to throttle input at all (it doesn't bog, just doesn't do anything) for maybe a half second.”source ↗

“When cruising between 10-15mph very slight throttle inputs will make it stutter in the 1k to 1200rpm range.”source ↗

“I have no idea where to start or what to throw money at first.”source ↗

“engine rpms intermittently stumble at idle and only idle. never surges, just stumbles.”source ↗

“this has been going on for 5 years in my duratec 2.0L. hasnt gotten better or worse.”source ↗

“im totally at a loss and have limited hope”source ↗

“It mostly happens in 2, 3 and 4th gear where I could be driving at the appropriate speed for the gear and it would start to shake uncontrollably, sometimes only slightly and other times pretty badly.”source ↗

“I’ve taken it to my mechanic twice for a quick check but they can’t seem to find the problem.”source ↗

“I just find it so weird that somedays it drives perfect and then another day it will do it constantly.”source ↗

“It started this literally yesterday, wasn't like this. I don't know if the piece im pointing at is causing this though, options?”source ↗

“My 2012 Mercedes e350 is making a rattling kind of noise when it’s idling. Does anyone know what could possibly be the reason for this?”source ↗