Side-to-side shake while accelerating between 28-52 mph

[mozartpc27]

So, three weeks ago I sank $700 into my 1987 2.5L Chrysler LeBaron to replace the distributor, logic module, and MAP sensor. This was because the car would start, but then stalled out immediately (i.e., would not hold idle). I was forced to take it to an unfamiliar mechanic because I was 100 miles away from home, and they identified the problem as one of fuel not getting to the engine. After ruling out the fuel pump, they made what turned out to be an unnecessary replacement of the distributor, before replacing the logic module (I got a used part for that) and the MAP sensor. This fixed the problem, and also restored the cruise control to working order (in retrospect, I wish I had mentioned the cruise control not working to them when I took it in - that probably would have clued them into the logic module and MAP sensor, rather than the distributor, and I could have saved myself $250).

Anyway, since having these repairs done, I have noticed a shake in the car that I don't recall noticing before this work was done. The shake is side-to-side, and occurs only when I am giving it gas to accelerate (i.e., not when I am accelerating by rolling down hill for example, only when I am actually giving it gas), and even then it only occurs within a range of speeds. The shake begins at about 28mph, gets more and more noticeable until it reaches a crescendo at about 40 mph, and then slowly tapers off until ceasing altogether at 52mph. If I take it up to 70 mph, and then have to slow down to say 53 mph, and then accelerate back to 70 mph, the car does not exhibit this shake, nor does it exhibit it whhile accelerating before reaching 28 mph, nor does it shake once it reaches a cruising speed within the 28mph - 52mph range.

So, first of all, what could be causing this? I first feared the automatic transmission, but the beginning and ending of the shake do not seem to match a shift in gears that I can hear. Because it happens on acceleration, I wondered if it might be something with the fuel injection system, like a fuel pump, which was partly what the mechanic I took it to last week was attempting to diagnose, which is why I wonder if this shake is related. I am also worried it could be an axle, or, as my friend suggested, a rotor. What do you all think?

[Pete in NH]

Hi,

I saw the picture you posted in another section of the forum, nice car. A warped brake rotor is more likely to cause a pulsing in the brake pedal when you apply the brakes than the shaking you describe.

You mentioned the distributor was replaced, the timing may not have been set correctly when this was done. Many mechanics today have no idea how to set the timing on a Chysler 4 cylinder. With the car in neutral, can you step on the gas pedal gentally and run the engine up smoothly or does it run roughly? My first guess would be if the car ran okay before the work was done but not afterward, it is something related to the work done.

If you know someone who has a timing light, I can tell you how to check and set the timing.

[Pete in NH]

Hi, Another quick thought I had was you might have a tire out of balance. A quick stop by a tire shop might confirm this.

[mozartpc27]

Hi Pete -

Thanks for those suggestions! I will check them out. With respect to the rotor, I actually have noticed, when slowing to a stop, what I would call a "pulsing," though I wouldn't say it was from the brake pedal itself, but rather it almost feels as if I can feel a warp in the rotation of something (the wheel?) as it slows to a stop. I am not really too great with doing car repairs myself (I am reading and trying to learn), so sorry for my vague description.

[K-CAR_WAGON]

Generally with a warped rotor you can feel the pulsation in the pedal. If you do think you have a warped rotor, check to see if one of the caliphers is hanging up making the one rotor more difficult to turn by hand than the other when jacked up.

In addition to normal tire out-of-balance issues, check your tires for any irregularities such as bubbles in the sidewalls or belt separtion issues causing portions of the tread to starting lifting. Also, if the car was sitting for a very long line in one position you may have flat sports on your tires.

A few other possibilites to check out: bad axle (CV joint), bad motor mount, bad tie rod end.

[mozartpc27]

Thanks for the ideas K_car_wagon. I will look into them!

[mozartpc27]

Silly me, I'd forgotten that I needed to buy the key to my hubcaps before I could get the tire balance checked (I think when I bought this car it was already missing said key). I was able to replace it from McGard, the OEM, and so I will get that checked out soon.

Another issue I'm having is that I get a very loud knocking sound when I turn the wheel HARD to the right (i.e., not on a "normal" right hand turn, only very tight ones). I am guessing CV joint (?), but I wonder if there are any other possibilities.

*Sigh* I want to keep the car running, but this will be a "running" fight with my wife I'm sure. By my count, here are some basic things I need:

Timing belt
Water pump (these two are just for standard maintenance, not sure either has ever been changed - car has 94K on it)
Power wash engine from previous oil leak
Valve cover gaskets (because there seems to be oil seepage around the head/spark plugs, but head was replaced 2 years ago, so it isn't that)
Air filter (not a big deal) and hose from air cleaning unit needs to be re-attached
CV joints (?)
Shocks/struts (?) - i.e., something in that wheel/suspension system
Wind shield wiper motor (hoping I can replace that myself)
And I am slightly worried about the starter. Again, not a big deal, just more money - I wish I were a mechanical sort, but I am not.

That's probably about $2,000 worth of work I just outlined there, maybe a little less.

I am just hoping I can get it to March as is, by then we'll have the money and I've convinced the wife to at least replace timing belt/water pump, although I am honestly not sure those are the most urgent needs. Problem is I am driving the car quite a bit not, 225-500 miles/week. Will calm down a bit down to 225/week, hopefully, but that's still close to a 1,000 a month.

But I love this car.

[Pete in NH]

Hi,

Good luck on getting through the winter months with your car, it can be very little fun working on them outdoors in cold weather. At 94K you're kind of on borrowed time on the timing belt. I never had one make it that far. Yes, it would be a good idea to do the timing belt and water pump at the same time as much of the same disassembly is required and there is no point taking the same stuff off twice. both are not hard to change but do require some tools and a place to work and might take a day or two to get through if you've never done them before.

If you run into CV joint issues and have concerns about the starter you may also want to change the starter if the driver's side axle shaft ahs to come out. I've never found a way to get the starter out without removing the shaft and again why take something apart twice.

On the valve cover gasket aviod those cork gasket sets and use the original RTV sealant or i've had good sucess with the newer one piece gaskets. They are a little pricey but work well.

Also, you may be able to save a little money on parts at rockauto.com although you have to watch the shipping charges and make a decision on buying locally or online.

Good luck with your car and popst any questions you have.

[Jacks1986Lebaron]

Not a mechanic by any stretch of the imagination, but my "86 was doing almost what yours is doing.

The passenger side ball joint had to be replaced......and the passenger side axle got replaced too.

Wobble/shake, and noise all gone!!

What gets me is I just had it in to rotate and balance all of the tires, and the guy who checked it all out told me everything looked good, except for tie rod end on the drivers side.

So I took it in to MY mechanic the next day after work, he said tie rod is fine, but the ball joint on pass. side is ready to fall out!!

good Luck and let us know what ya find out!