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Discussion Starter · #1 ·
I just bought a 93 LS this summer and I have noticed a few things wrong with it. However, my main concern is that each time I am in the range of 60-65 MPH (3100 RPM) the car begins to vibrate heavily. The vibration is present all the time at this specific speed and I have noticed the hood shaking. The car seems to be lazy sometimes when accelerating and the transmision gears down (its an auto)immediately after I remove my foot from the accelerator. I notice that I begin to decelerate at a considerable rate. I have not changed the transmision oil yet and the service records from the previous owner indicates that he hadn't done that for at least a couple of years also. Somehow I think it may be alot more than just changing the oil. The car idle is way to high at around 1300.

Here are a few facts about the car.

117,000 miles
New distributor (installed last year by previous owner)
New engine oil (synthetic put in last month)
There are no oil leaks in to the spark plug wells.
The stock wire set is still in place.
The CV boots are still in good condition.
Engine does not shudder when reving at park at any RPM

I think I'll get the TPS replaced. I have read that the TPS can cause all sorts of engine trouble so I'll just play it safe with a new one. Is it possible that I have a problem with my drive shaft or could it be a bad transmision? Do you think a mechanic has a good chance of diagnosing this correctly? I appreciate whtever help you guys can give me.

Thanks, Ray
 

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Hey Welcome to the board Ray. We need more members in the Automatic community here, but it definately sounds like a tranny. Take it to any transmission shop for that and that should do all the diagnostic for free. You will probably have to leave your car there for a few hours though. As far as your car's decelleration problem, have u pulled up the e-brake lately. Check and make sure it has been released all the way from underneath your car. A common problem with this is it does not fully release and this causes decelleration and horrible brake wear. Hope this helps.
Dave
 

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As Dave said, it is most likely the tranny, but if your mechanic doesn't find anything wrong with it, it could possibly be tire balance.
 

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Discussion Starter · #5 ·
Could it be the alignment? The car is extremely smooth on all other speeds including those above 70 mph. I have just equalized the tire pressures and still have the vibrations. If it is the tranny... it's going to hit my wallet isn't it?

Also guys there is a sharp hissing sound from the engine, like tightly flowing liquid. Is this normal or should I be concerned?
 

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speedy,

As far as the idle goes, definitely get the TPS adjustment checked. You can do it yourself:

- ground the TEN pin in the Diagnostic box (beside the battery)
- turn on the ignition but don't start it
- if the cooling fan comes on, the TPS needs adjusting
- if the fan is off now, crack the throttle a little bit (like 0.030" off the top screw) and make sure the fan comes on. If it doesn't, the TPS may be defective or out of adjustment.

If the TPS is in adjustment, the car probably needs the idle air re-set.

Vibrations at very specific speeds typically points to a tire defect: a shifted belt, broken carcass, severe flat-spot etc. It can also mean that a tire(s) has thrown a balance weight. Can you identify if the vibration comes from the fron or the rear? If it's localized like this, try rotating the tires front-to-back to see if the vibration follows the tires. While they are off the car, have them balanced. While the tires are spinning on the balancer, a good tech (or yourself) can often pick-up a defect as the wire may "wiggle" as it rotates.

A maldadjusted or defective TPS could affect transaxle shifting since the TPS is one of the inputs to the PCMT.
 

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Discussion Starter · #8 ·
Thanks Mike, I'll have the tires balanced and rotated. The vibration is definitely coming from the front of the car. I will also start with getting the oil changed but I'll keep in mind what you said JP. Aside from these vibrations the ride is quite smooth. I believe the bucking can be attributed to a faulty TPS. The idle speed control is part of the TPS so it all ties together. I hope that having the TPS replaced/calibrated and the much needed oil change will rid of the downshifting when I remove my foot from the pedal. It should also resolve the hesitant acceleration. If not than I guess I'll have to rebuild/replace the tranny - hope not. I was concerned that the vibration may have been a slightly bent/warped drive shaft or a broken CV. Could this be it? The ride is very smooth at all other speeds other than 60-65. Thanks.
 

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Usually, the vibration you are describing is because of a tire. Bad balance, defective tire, all sorts of things.

Does the tranny shift well when you drive it normally? As far as the down shifting when you let off the gas, I would love to know what causes that--my 1985 Lincoln Town Car does that--and I've always wondered. When you find out, let me know. I don't feel that it is a serious problem, it is just annoying. Definetly wouldn't hurt for you to get the tranny serviced at the Dealer. The bands may need adjusting also, probably do after 100K miles.

Good luck, I'm sorry to hear of you having problems.
 

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Discussion Starter · #10 ·
Yes it shifts fairly well. It may thuck sometimes but not severely. I'll let you know when I get it fixed. First things first however. i've got to get rid of that vibration. The 60-65 range is the regular flow of traffic here at the Jersey turnpike during morningtime and I hate having to go slower than the rest of the crowd and fast enough to get a ticket.
 

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My auto LS 97 had a shudder at 45 mph at ~2500rpm. The shudder was followed 200 miles later by the overdrive engaging earlier than it should, and this quickly progressed to no power in D or OD, I had to drive with the car in 2nd. The dealer ended up replacing the trans under waranty. The shudder did not come from a specific point, if anywhere the drive wheels seemed to be the origin (of course).

I've got a question for auto owners. At night, the shifter has the letters indicating the gear which are lit, and next to that are little windows that have an orange indicator for the gear. On your auto, are the other windows blacked out except for the orange indicator, or are all the little ovals lit, including the orange one?

[Edited by Slippy on 12-03-2000 at 05:13 PM]
 
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