What is causing my engine to vibrate at low RPM?

November 13, 2005 2:07 PM

Why does my car vibrate at low RPM and idle? It occasionally gets very close to stalling out at low RPM and idle as well. I'm starting to worry because the Cleveland winter is approaching.

It's a '97 Hyundai Elantra standard transmission with all scheduled maintenance and regular oil changes, etc. I've had it examined by two Hyundai dealership service departments and two independent mechanics that have found nothing wrong, but the problem persists and gets significantly worse in winter. I've had the timing belt, clutch, all serpentine belts and fuel filter replaced in the last year. Is there anything I'm missing? Do others have similar experiences?

posted by vkxmai to travel & transportation (13 answers total)

are you letting it warm up? my car kinda hesitates, and in very cold (for this area) weather it has actually stalled out (I have a '99 BMW 528iT which didn't have any problems with it when I took it in last). the warmer the engine gets, though, the less.. "violent" (for lack of a better term) the hesitations get; once it's fairly warm, it's fine. doesn't do it at all in the summer.
posted by mrg at 2:27 PM on November 13, 2005

I had the same problem with my '93 Saab, but that was an automatic transmission and it would stop vibrating when I put it into neutral. It would still stall though. I was told that it had something to do with the front axle and driver (on the car, not me). I ended up getting a new car about a month and a half ago, and never got it repaired.
posted by amro at 2:33 PM on November 13, 2005

My previous car, a 91 Chrystler LeBaron, did the same thing, I think it was a mounting bracket for the engine that had become loose.
posted by borkencode at 2:38 PM on November 13, 2005

The Hyundai Elantra, like most newer cars, has a balance shaft belt meant to counter vibrations like those. The likeliness that something is wrong with your balance shaft or its belt and that not being completely clear to those who have looked at your car is extremely low, it's there.

The more likely cause (disclosure: I am not a mechanic) in my mind is that it may have something to do with your oil. You say you have regular oil changes—are you changing to a winter-capable oil? Low temperatures do amazing things to your car's engine oil, altering its viscosity and making it harder to serve its purpose. Search Google for "winter motor oil" for more details on the best type to you and see also your car's owner's manual for details.

I'm sure some others will have some ideas as well, since problems like these can always have the most obfuscated of root causes. Good luck.
posted by disillusioned at 2:40 PM on November 13, 2005

You don't say whether it's a vibrating more like a "buzzing" (like that of a cell phone), or more like a very fast "rocking/bouncing".

If it's the latter - I would have your spark plugs and spark plug cables checked. I had a spark plug or two not firing properly at low/no speed on my old car, and it caused my car to shake / vibrate at slow speeds and at idle. Once I got up to speed, this problem seemed to go away.

This can cause wear and tear on your engine and should definitely be looked into. It shouldn't be very expensive at all to replace all spark plugs and spark plug cables. If the car is a '97 and has never had this done - it couldn't hurt to just do it anyway for the sake of having new parts in there.
posted by twiggy at 3:59 PM on November 13, 2005

I had a similar problem in warm LA weather. Turned out the O2 sensor was dead and screwing with the computer that regulates things like RPM and whatnot.

(I wasn't going to mention it until borkencode's comment, but I also had a busted mounting bracket at the time.)

Seems unlikely that two mechanics would miss such a thing, but that's what happened to me. Once I got it fixed, no problems. 98 Honda Civic automatic with all regular maintenance.
posted by samh23 at 4:09 PM on November 13, 2005

I will have the O2 sensor looked at--and my spark plugs/wires were replaced right after I bought the car. I think a problem with the O2 sensor might be so small that a mechanic might not look for it unless a pretty serious problem was manifesting itself.

It is most certainly a rocking/stalling feeling and not a buzzing.
posted by vkxmai at 6:30 PM on November 13, 2005

Could be fuel pickup or a clogged or failing injector.
You might want to try adding a bottle of Techron to a tank of gas and see if that clears things up.
posted by Thorzdad at 9:18 AM on November 14, 2005

What Thorzdad said, (get the Techron concentrate) plus check all your vacuum hoses. They get old and brittle with age, as do we all, and a little crack in one can throw off your engine management systems.
posted by Floydd at 9:51 AM on November 14, 2005

I was going to suggest a vacuum leak, so I second Floydd's post. Vacuum leaks can cause erratic idle. (Wasn't he in Monty Python?)
posted by Kirth Gerson at 12:50 PM on November 14, 2005

I don't think it's the O2 sensor, because just about any '97 car uses OBD2 diagnostics which will throw a hissy-fit with defective O2 sensors (and show up as a check engine light).

Does this only occur at startup? If it's only at startup, you should switch to a lower viscosity oil for starters. 5W30 or even 0W30 if you can find it.

If it happens intermittantly, but particularly when the car comes to a stop at lights or stop signs, the problem could be a vacuum leak or (my guess) an intake problem. You might need to clean the throttle body. If you go this route (or have someone else go that route for you) make sure they use a throttle body cleaner that's safe on Teflon. Many butterfly valves are coated with a substance that is sensitive to harsh TB cleaners--and if you accidentally scrape the coating off, you'll have worse idle droop than before.
posted by Civil_Disobedient at 6:48 PM on November 14, 2005

The vibrations occur all the time, but mostly when I am slowing to a stop at a red light or stop sign or when I am stopped/idling. When I switched from using BP to Shell/Amoco in the winter, the vibrations seemed to be less severe, but they were still present. Today when I drove (it was 49F and rainy in Cleveland) the car vibrated especially at stops. I'm going to bring it to the shop and ask them to check the various things you have mentioned so far.
posted by vkxmai at 9:16 PM on November 14, 2005

If anyone happens to read this--I had the car looked at yesterday and they said that one of the cylinders wasn't "firing" but that it only happened twice and then they couldn't get it to repeat it self after five other times driving it during the day.
posted by vkxmai at 8:58 AM on November 19, 2005