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Any ideas on the most severe idle vibration I've ever felt!?!

Hey guys,

I’m at my wit’s end, so I’ve come to the geniuses, yeesh.

If you guys are familiar with Ford Escort ZX2s and a very, very, VERY rough idle, I’d really appreciate your advice.

The car’s always had a rough idle - either when at a stoplight and the car’s in drive but stopped or sitting still. When I shift into neutral the idle gets smoother but there’s still a slight vibration throughout the whole car.

It’s now gotten so bad that even shifting to neutral doesn’t help. Literally the steering column vibrates about an inch up and down and the entire seat shakes.

I thought it was a motor mount degradation issue so I had those replaced about 6 months ago but it didn’t do much. The only thing that I can think of is before my alternator was replaced, the check engine light was on and the code was for a bad O2 sensor.

Could a bad O2 sensor make the car idle this roughly? Since they unhooked the battery, the light is off now and I can’t get the code to see which sensor it is. Would it be helpful to replace the sensors to correct an extremely rough idle?

Oh, I notice that when the AC is off, the vibration it’s as bad either.

Thanks for your help and any advice you have! My chiropractor will hate you, but I will adore you!

That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here.

Hey -

I can’t remember the code but I had it taken in and read and it was an O2 sensor problem. When I had my alternator replaced, the codes were reset - I was just wondering if a faulty O2 sensor could be the cause of a very, very rough vibration when idling.

No, an oxygen sensor is not going to cause a vibration. Does the vibration go away if you rev the engine, or get worse, or is it only when idling? And it vibrates in park, reverse, neutral and drive? Does the vibration change in different gear selector positions?

Given that you’ve had the mounts replaced, then your car is just running poorly.

What year is it? How many miles are on it? How old are your spark plugs & wires? Air & fuel filters?

There is no code that will tell you that you need a new O2 sensor. There are codes that tell you that you are running lean or rich, and a lot of people think that those codes mean you should replace the O2 sensor. Well, that’s sort of like installing a burglar alarm and assuming that the alarm needs to be replaced if it ever goes off. There are other kinds of codes that would point one to investigate the condition of O2 sensors, but I am going to assume you are running too rich or lean.

Ever check the fuel pressure? Check it for vacuum leaks, including around the intake manifold gasket. Pull off & clean your idle air control (IAC) valve, clean the throttle body & MAF sensor. Check the operation of your EGR valve. Check the intake tract for splits or other leak points.

Thanks for all the suggestions. It’s a 2003 and there are about 95,000 miles on it. I’m not sure how old the spark plugs, etc., are. I’ll def try cleaning the recommended things.

Yes, the vibration is only present when I’m not driving. If I rev the engine when in neutral, it goes away. But when stopped, the entire front of the car vibrates so much I’m almost bouncing in my seat! I can really feel it through the steering column and also, thismay be unrelated, but I can feel and hear something rattling on the driver’s side below my foot when it’s shaking.

It used to be worst when in drive and I could shift to neutral and it would go away. Now though, even switching to neutral doesn’t help.

Well, I’m glad to know that replacing the O2 sensors won’t correct it. I’m kind of worried that I was charged for new motor mounts and they weren’t actually replaced.

Should I just go in and ask for a tuneup or something? I’m getting frustrated because I shelled out $600 for motor mounts and another $600 last week for a new alternator. Geez!

Thanks for your suggestions, though!

“I’m not sure how old the spark plugs, etc., are”

Do you have an owner’s manual for this car? If not, get one. Open it up to the parts that describe the maintenance schedule. Get everything done that is even close to being due (noting that some things are pinned to mileage OR time). What you probably have is a simple case of neglected maintenance.

Get new plugs in the car ASAP, and use the plug recommended as the OEM plug. You may need some new plug wires and boots too. If this is a coil on plug set up one or more of the coils might be bad. The car is not hitting on all cylinders at idle, and as revs pick up this will mask the problem.

Once you have all the plugs, wires, and coils replaced if the vibration is still present get a compression check. You may have one or more cylinders with low compression. These “low” cylinders may not fire at slow speeds (idle) but might fire at higher rpms and therefore the motor will smooth out.

If the compression is low on one or more cylinders you have a “tired” motor. The question is where are you losing compression? The low compression could be worn rings; or burned, bent, or misadjusted valves. It will take more test to determine how to proceed to fix the motor.

Back in the bad old days when we had idle adjust screws, you could possibly have gotten around this just by tweaking the idle a bit. Nowadays, you get to figure out what’s really wrong. And there is a long list of possibilities. The most common causes are probably a vacuum leak, spark plug wires in need of replacement, and accumulated crud in the air intake, but there are many other possibilities. Some problems should trigger a check engine light, but some don’t. As others have told you, a failing O2 sensor won’t normally cause vibration although I suppose it is remotely possible that it might somehow cause an improper fuel mix. But I don’t think that the O2 sensors are even looked at for the first few minutes of car operation (they have heaters that take a few minutes to warm up), so if the vibration is still there first thing in the morning, it’s probably not an O2 sensor problem.

You might want to check the harmonic balancer to make sure it’s not loose. If it is… make sure it’s torqued to the proper specs.

Dead miss on more than one cylinder could qualify.

. . . Or Coming Apart And Wobbling.


These are the basic things you need for a good idle on a 4-banger.

Good and balanced compression on all four cylinders. A compression check is in order.

Good spark on all four cylinders. There are a few way to verify this. Assuming you don;t have a scope at your disposal, attaching a timing light with an inductive pickup to each wire can identify one that isn’t firing properly at idle. Remember that you’re using the light to check firing, and you can check the timing while you’re on the #1 wire.

Good fuel pressure. Easy to check.

clean operating injectors. You don’t say the year or miles on this car, but this strikes me as a good possibility to check for.

An intact harmonic damper, as Missileman suggested, although usually that’ll cause horrible vibration on acceleration if there were a problem. Check it.

Valves that aren’t sticking. Vacuum gage, anyone?

No vacuum leaks. No where DID I leave thet vacuum gage?

What I’d recommend doing is checking each of the items on the list one by one. They’re all affordable, none is technically deep, and all are good possibilities. Post back with the results.