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Light Shudder On Acceleration

 
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  #1 (permalink)  
Old 22 Nov 2010, 09:31 pm
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Posts: 295
Default Light Shudder On Acceleration

I am getting a light shudder on acceleration.
It goes away once I hit 40 kph.
It not major, just a little hesitation or shudder.
Makes it difficult to tell if it's the engine or the suspension.
When I was a kid I drove cars with "points".
When I drive my PT it feels just like the points are going or are not properly gapped.

Things I have done and checked:

1- I put in new, properly gaped plugs
2- I put in new good quality wires
3- I changed the oil
4- I changed the oil filter
5 -I changed the air filter
6- I checked for wear in the wheel bearings
7- I checked for wear in tie rods and ball joints
8- The tires were changed for winter and are freshly balanced
9- I have no codes

When I pulled the old plugs they were properly worn, no unusually wear and tear, no oil stains, no carbon fouling, nothing chipped or broken.

Car starts up properly and runs great except for the acceleration between 0 and 40 kph.

Needless to say the PT has no "points" so I am not sure what to look at next.
Anyone have any ideas, I sure be glad to hear from you

Thanks
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Old 22 Nov 2010, 10:11 pm
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Posts: 27,743
Default Re: Light Shudder On Acceleration

Check your motor mounts.
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Old 22 Nov 2010, 11:44 pm
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Default Re: Light Shudder On Acceleration

Quote:
Originally Posted by CREWZIN View Post
Check your motor mounts.
Will do

I am looking for worn bushing and or loose bolts I assume?
I have to admit I have never checked the motor mounts before.
Any input you could give on how to test them would be appreciated.

By the way two thing I forgot to mention:
1- Petunia has 51,000 kilometers on her.
2- I did the battery disconnect after changing the plugs and wires to re-teach the computer.

Last edited by bob2006; 22 Nov 2010 at 11:55 pm.
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Old 23 Nov 2010, 07:11 am
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Default Re: Light Shudder On Acceleration

Battery dis-connect never hurts anything if you do it right.

Watch the engine when you start the car and see how much shaking it does.

Don't stand in front of the car while someone watches the engine. Other person gives it gas (petrol where you come from) and puts in in gear and the brake at the same time and watches how much the engine torques over. Excessive movement means too much play in the mounts.
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Old 23 Nov 2010, 10:17 am
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Default Re: Light Shudder On Acceleration

Quote:
Originally Posted by CREWZIN View Post
Battery dis-connect never hurts anything if you do it right.

Watch the engine when you start the car and see how much shaking it does.

Don't stand in front of the car while someone watches the engine. Other person gives it gas (petrol where you come from) and puts in in gear and the brake at the same time and watches how much the engine torques over. Excessive movement means too much play in the mounts.
Thanks Crewzin
Going to have to find a partner to help me with this.
As soon as I do, I'll let you know how it went.
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Old 23 Nov 2010, 10:23 am
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Location: Mooresville, NC
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Default Re: Light Shudder On Acceleration

Is this an auto or manual tranny? After you do Crewzin's suggestion, if there is no excessive shudder, then you might look to drive train.
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Old 23 Nov 2010, 11:47 pm
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Default Re: Light Shudder On Acceleration

Well it's not the motor mounts.

After a lot of driving around tonight I narrowed down the range of shudder.
It seems to be taking place in second gear, between 20 and 40 kph.

As Chromenut suggested I am now looking at the drivetrain.
Has anyone here had a similar experience?

Does anyone now if there is some electronic module that controls firing of the plugs?
I would look at that too.

I checked the transmission fluid at full hot and it's properly full as it's always been since I got the car and there are no detectable leaks anywhere.
I checked for codes again and still nothing only a "done"
Does anyone know if transmission faults throw a code?

My PT is 2006 Automatic with 51000 km on it.

Thanks for all input It's always appreciated.
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  #8 (permalink)  
Old 24 Nov 2010, 12:35 am
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Default Re: Light Shudder On Acceleration

Found this in a 2003 PT Service Manual:

ENGINE MISSES ON ACCELERATION
1. Dirty or incorrectly gapped spark plugs.
1. Clean spark plugs and set gap.
2. Contamination in Fuel System.
2. Clean fuel system and replace
fuel filter.
3. Burned, warped, or pitted valves.
3. Replace valves.
4. Faulty ignition coil(s).
4. Test and replace as necessary.

Can anyone tell me how to test the ignition coils?
I cannot find a test procedure in the manual.
Seems like a good place to start.

Thanks for all help
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  #9 (permalink)  
Old 24 Nov 2010, 07:31 am
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Default Re: Light Shudder On Acceleration

Bob,

I would think if it was the coil, it would happen all the time, not just at certain speeds. The transmission would throw a code, usually P0700 which is generic and a scanner needs to be used to pinpoint the problem. The firing of the plugs is controlled by sensors (Crank and Cam) and the computer and again, don't think it would happen at particular speeds.

You might want to pay someone with a lift to get your PT into the air so a mechanic can watch the drivetrain from start to past the speed where you have the problem as Chromenut suggested.
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Old 24 Nov 2010, 10:17 am
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Default Re: Light Shudder On Acceleration

Quote:
Originally Posted by CREWZIN View Post
Bob,

I would think if it was the coil, it would happen all the time, not just at certain speeds. The transmission would throw a code, usually P0700 which is generic and a scanner needs to be used to pinpoint the problem. The firing of the plugs is controlled by sensors (Crank and Cam) and the computer and again, don't think it would happen at particular speeds.

You might want to pay someone with a lift to get your PT into the air so a mechanic can watch the drivetrain from start to past the speed where you have the problem as Chromenut suggested.
Thanks Crewzin for the answer.

So when you say "drive train" you think that there might actually be some physical slipping that would be observable?
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