2003 Towncar Shakes in Idle

Kev7770

New member
22
5
3
Hello!

I have a 2003 Executive that vibrates intermittently while in park or while coasting in parking lots (<10mph). I had both motor mounts replaced and that cut down on the vibration greatly, but I'm still getting some irregular vibration that I consider to be excessive. I would also like to note this ONLY happens when it is cold outside. During summer months it's fine.

I also have new spark plugs, fuel filter, air filter, so I can rule those out. Could it be the tranny mount? Anyone experience something similar?
 

CuttingToolGuy

Well-known member
385
1
296
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Houston
Since this seems to be intermittent and you do not indicate any warning lights I think you may need to get a data logging program and record what the car's computer sees.

Here is an example of Forscan Lite:


The way this works is you buy the software añd load it on your cell phone and an adapter that plugs into the OBDII port of your car. Then when you start the car the phone records everyting the car computer sees. You can match the data with the stumble and then identify what the computer thinks is causing it.

Note: I am not endorsing the Forescan Lite as I have not used it. Forescan itself does have a good reputation.

If you want to guess, I would suggest that you check the resistance of your ignition coils to see if 1 is different from the rest.
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Kev7770

New member
22
5
3
Since this seems to be intermittent and you do not indicate any warning lights I think you may need to get a data logging program and record what the car's computer sees.

Here is an example of Forscan Lite:


The way this works is you buy the software añd load it on your cell phone and an adapter that plugs into the OBDII port of your car. Then when you start the car the phone records everyting the car computer sees. You can match the data with the stumble and then identify what the computer thinks is causing it.

Note: I am not endorsing the Forescan Lite as I have not used it. Forescan itself does have a good reputation.

If you want to guess, I would suggest that you check the resistance of your ignition coils to see if 1 is different from the rest.
Thanks so much for your reply! I got a Bluetooth OBD2 adapter and used a different app. I did notice the RPMs drop dramatically when the vibration was occurring.
I cleaned the throttle body and I’m currently taking parts off to access the IAC. I will try cleaning that or maybe just replace it.
 
87
25
18
Thanks so much for your reply! I got a Bluetooth OBD2 adapter and used a different app. I did notice the RPMs drop dramatically when the vibration was occurring.
I cleaned the throttle body and I’m currently taking parts off to access the IAC. I will try cleaning that or maybe just replace it.
Let us know when you find the cause and the fix.
 

Kev7770

New member
22
5
3
Let us know when you find the cause and the fix.
I cleaned the IAC and reinstalled it, but the problem is persisting. The new IAC came in yesterday so I hope to install that this week.

If that doesn’t do anything I’m going to have the transmission mount replaced.
 
87
25
18
I cleaned the IAC and reinstalled it, but the problem is persisting. The new IAC came in yesterday so I hope to install that this week.

If that doesn’t do anything I’m going to have the transmission mount replaced.
How are the plugs and wires? Bad combo will cause shaking...
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Koach

New member
10
3
3
I replaced my plugs/coils about 6 weeks ago and experienced some odd behavior afterward (2006 w/118k); it would idle smooth most of the time, but every once in a while it would idle somewhat rough...not bad, but just not smooth. Then it stalled at a stoplight which was a first time 'oh sh*t' moment. It happened a few days later while rolling about 60, then again while stopped, but it was completely random and never had any codes present. After a quick search it seemed that MAF, cam/crank position sensors could cause this and since I removed the air intake system to change the plugs...I removed the connector, sprayed cleaner and applied dielectric grease. Another possible contributor which probably isn't related to your situation, but I had also used all my generator gas (20gal) and did the end of season dump into the Lincoln/Wrangler. Even though I had used Sea Foam the Jeep was very noticeable with a weird idle that eventually went away and I thought this too could've been a contributor to the rough idle/stalling. After a few tanks of gas and the connector cleaning I never (knock on wood) had it recur.
 

wolf_walker

Junior Member
379
217
43
Thanks so much for your reply! I got a Bluetooth OBD2 adapter and used a different app. I did notice the RPMs drop dramatically when the vibration was occurring.
I cleaned the throttle body and I’m currently taking parts off to access the IAC. I will try cleaning that or maybe just replace it.

Forscan will show you at the same time what the requested idle speed is by the ECU and the actual idle speed, generally if they two don't match the ECU will complain about it. Mine has always acted funny idle wise, I replaced the IAC early on but it's still fairly slow and lazy to respond. Other than on winter cold starts where it does the overly high initial idle speed. I was idling through a parking lot the other day and yanked hard on the steering wheel and it took it long enough to respond to the load that the alt light came on due to low rpm for a split second. Nothing I've ever done has affected this, idle is ever so slightly not smooth either, though oddly you can only tell it from the cabin, not with your hand on the running engine which seems quite smoothe. I figure I'll circle back around to it eventually.
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