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I bought a 98 Corolla with about 90,000 miles on it a few months ago. It's been fine, but lately I've noticed the engine shaking while in idle and warmed up. While at a stop light, I can see the hood vibrating, and feel it through the frame of the car. Revving it anywhere above 1000 RMP (It idles around 600) seems to immediately remove the vibration. It's smooth as silk when accelerating, no engine vibration at all while driving at anything above residential speeds. No CEL, oil changed recently, air filter is clean, PCV valve is brand new, passed smog. (Barely.) Spark plugs are new, and of the correct type. Spark plug wires are new, and installed correctly. The throttle body isn't completely clean, but throttle body cleaner doesn't remove the faint residue that remains. The 98 Corolla has a MAP sensor rather than a MAF sensor, which rarely needs maintenance, apparently. The economy is slightly lower than it should be; I'm getting 20-24 in residential areas and up to 34 on freeways; I understand it should be about 28-38 with average driving habits. I'm poor right now, so I haven't had a mechanic look at this issue specifically. It did pass a basic safety inspection by two separate mechanics prior, so I imagine it's nothing world-ending, but it is worrying me. [EDIT]: Wait poo poo I meant to put this in the stupid questions sub wat do thehiddengecko fucked around with this message at 08:00 on Oct 15, 2015 |
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Oct 15, 2015 07:56
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Engine mount
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Oct 15, 2015 08:28
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jjd74 posted:Engine mount Yeah I'd have a look at the mounts, especially if it's not throwing a CEL.
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Oct 15, 2015 18:46
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jjd74 posted:Engine mount
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Oct 15, 2015 19:02
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What everyone else said. There's probably 3. One is relatively easy (usually on the passenger side), one is moderately difficult (between the radiator and engine), one is a serious pain in the rear end. The one that's a serious pain in the rear end (firewall side of the engine) is the one that's likely in the worst shape, if it's an automatic. The easy one is also probably in rough shape. Some jack stands (or ramps), a block of wood (to go between the jack and oil pan, so you don't dent the pan), a good jack, and hand tools should be all you need to change them, assuming little to no rust. Also a lot of swearing while you're trying to line everything up for a new mount.
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Oct 15, 2015 23:37
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some texas redneck posted:Also a lot of swearing while you're trying to line everything up for a new mount. I broke down and bought a drift pin to complement my toolbox, it's perfect for lining up bushings and suspension components before stringing bolts through them. Maybe like $10, but they save your screwdrivers and I ended up using mine for a ton of stuff.
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Oct 15, 2015 23:52
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some texas redneck posted:What everyone else said. There's probably 3. One is relatively easy (usually on the passenger side), one is moderately difficult (between the radiator and engine), one is a serious pain in the rear end. The one that's a serious pain in the rear end (firewall side of the engine) is the one that's likely in the worst shape, if it's an automatic. The easy one is also probably in rough shape. Yeah, I had considered the engine mounts as a possible cause. Is it important to replace them for the longevity of the car, or is it just a matter of comfort as long as the shaking isn't awful? Also, I had no idea you could reinstall them on your own - I thought you had to lift the engine! So I can just swap them out by putting the car up on axle stands and doing them one by one? (Probably the firewall one, since it is indeed an automatic.) A full set of mounts seems to be obtainable for under $100.
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Oct 16, 2015 07:58
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You do need to lift the engine, and if the mounts are particularly worn, you'll need a jack with wheels (so a basic $30-40 hydraulic floor jack), since the engine will need to be repositioned a bit - however, you can usually do so using a decent hydraulic jack and a block of wood. It can be done using a good floor jack (preferably a hydraulic one with wheels) and a block of wood. Basically, you lift the car enough to get to whatever mount you want to replace (with the car on either ramps or jackstands - never while it's sitting on a jack), then place your jack under the oil pan. Place a decent sized block of wood between the jack and oil pan (the block of wood needs to be wide enough to go end to end on the oil pan - a scrap piece of 2x4 works very well) - the block of wood spreads the weight across the oil pan, and prevents you from damaging the oil pan and oil pickup. The short version is you lift the engine just enough to get the weight off of the mount that you need to replace, remove the mount, install the new mount, and invent new swear words while trying to get the engine lined up with the new mount (especially the rear mount). As NoWake mentioned, a drift pin will come in very handy, but even a cheap screwdriver will come in very handy to line things up. It sounds worse than it is, but it's not that much worse than doing a brake job. The rear mount is a bitch on most FWD cars, but the hard part is just getting it lined up once you're trying to install a new mount. That's why I recommend a hydraulic jack with wheels - I have AutoZone's cheapest rolling 2 ton jack, and it works fine for this and most other stuff I've used it for (I think I caught it on sale for $30). You do need to replace them eventually - driving with them collapsed/worn out will put some extra strain on your CV joints (as the engine and transaxle will sit a bit lower in the engine bay, possibly even at a different angle than they're designed for - I had one car that had one side of the engine sitting several inches lower than the other side), but as long as you get to it eventually, it's (usually) not a massive deal aside from comfort and rattles. If you're not comfortable wrenching on your own car, I'd probably have a shop do the rear mount, as it's the biggest pain in the rear end and usually the hardest to line back up. With a lift, it can be done in an hour; same if you have ramps/jackstands and a jack that can lift the engine 2-3 inches. Same goes for the other mounts, the rear is just the biggest pain because it's usually a very cramped area. If you're in a rust-prone area, I'd really suggest having an impact wrench handy. I've had to use a BFH (big loving hammer - I have a ~10 or 15 pound sledge hammer I use to wail on a wrench when a bolt won't break loose) on plenty of crap, including motor mounts. Usually have to use it on brake and suspension parts though. randomidiot fucked around with this message at 09:06 on Oct 16, 2015 |
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Oct 16, 2015 08:57
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To diagnose an engine mount you should have a buddy stand on the brake while in gear and have him or her hit the gas pedal in drive and reverse and watch the engine mounts. Dont go hog wild cause its not great for your transmission but a few times should give you a good idea of what engine mount is moving if any. Alternatively could be a vacuum leak caused misfire. You got a check engine light? Preoptopus fucked around with this message at 22:23 on Oct 16, 2015 |
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Oct 16, 2015 22:20
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some texas redneck posted:You do need to replace them eventually I once drove a Corsica for a few months that had utterly obliterated mounts. On engine braking it would flop against the firewall and the whole car would vibrate like you'd stuck an industrial-sized Magic Wand to the roof. Never did do anything catastrophic, but that car had two wheels in the grave by that point anyway and was receiving nothing but enough fluids to keep it mobile.
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Oct 16, 2015 22:36
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IOwnCalculus posted:I once drove a Corsica for a few months that had utterly obliterated mounts. On engine braking it would flop against the firewall and the whole car would vibrate like you'd stuck an industrial-sized Magic Wand to the roof. Never did do anything catastrophic, but that car had two wheels in the grave by that point anyway and was receiving nothing but enough fluids to keep it mobile. The first thing broken engine mounts break is usually the exhaust.
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Oct 16, 2015 22:38
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My Protege had blown mounts and in addition to rattling against the firewall a whole bunch (which is how I noticed it), it strained my stock midpipe to the point that it cracked between the two cars when I went over a bump one day.
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Oct 17, 2015 02:38
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