2005 V6 shudder at idle in gear

1969 Mach

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Aug 18, 2020
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Hi, new to the forum, and my daughters 2005 V6 auto coupe has the most annoying problem. She came home and said that at the stoplights with the AC on, the car shudders and vibrates. We went out and drove it, and confirmed. It gets a little worse when the high-speed fan kicks on at the radiator too. As soon as you put it in neutral or park it’s fine.

It has 171,000 miles on it, but has been very well taken care of and runs excellent anywhere above and idle, with no other driveability issues. No codes either. I went ahead and replaced the spark plugs and wires, and it made no difference. I then replace the throttlebody assembly with a brand-new one and did the re-learn, and it seems like it might be a little better, but it’s still there and she can even feel it. I cleaned the mass airflow sensor, checked the TSB on the exhaust hanger/transmission crossmember issue and removed both of those hangers and isolators, but little to no difference. She absolutely loves her car but this drives her nuts. Any ideas?
 
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Bullitt95

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Jun 13, 2007
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You said the car shudders in D but is fine in P and N, so it sounds like there might be a fault inside the auto tranny.
I suggest you replace the tranny fluid and filter (do not flush) as a first measure to see if that improves things.
 

don ruggles

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Jan 11, 2013
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No, it's the amperage draw on the high speed fan, i think. BUT I also had to replace the harmonic balancer(crank pulley) so that may also factor in. The fan is supposed tp go to low speed first and then to high.
 

1969 Mach

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Aug 18, 2020
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I replaced the MAF last night as it was also original to the car and getting old, and it was maybe a bit better(not worse) but the vibration is still there. I’m going to replace the motor mounts ASAP (which was my first thought anyway) as well as the trans mount. All are OEM, and with 15 years and 170,000 miles, I don’t mind doing it for her sake. I do not usually throw parts at a problem but these are almost all old and somewhat worn parts anyway, and it’s her baby. She’s a Mustanger for sure!
 

1969 Mach

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Aug 18, 2020
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Just wanted to finish this thread, the problem is now solved. I decided to go ahead and replace the motor mounts with OEM Ford mounts. I chose not to “cheap out” and go with any aftermarket mounts of any kind. The old saying of don’t try to beat millions of dollars of engineering and testing just to save a few dollars was very true in this case. They didn’t let this car leave the factory new with that problem, and figured out how to solve it at the factory. I wish they would do that with every issue! Anyway, do not waste your time and money going with questionable quality parts here, as it’s too much time and money to have to do the job twice. Other mounts would be fine for a race car, but this is 100% street driven by our daughter.

The OEM Ford motor mounts solved the issue, there is now very little if any vibration felt now at an idle while in gear, and the AC on. You can still feel the slight engine “shudder” if you lay your hand on top of the intake while it is idling but the motor mounts are now isolating the vibration from the chassis. I do realize that these V6’s unfortunately are not as smooth as glass anyway, but anything over an idle and going down the road, the car was always fine. The problem was just at an idle.
You could tell by looking at the original mounts that they looked a bit crushed and possibly appeared worn, but otherwise were not damaged and the engine had not been leaking any oil or fluids onto them. They were very clean and dry. So in other words, just by looking at them you cannot necessarily tell that they are definitely bad or worn, but considering the weight that they hold and the job that they do, common sense told me that I was doing the right thing by replacing them. It took a few hours to replace them but it was all nut and bolt work. You must be careful lifting the engine off of its mounts, I used a small block of wood on the oil pan rail and balancer flange, right where it meets the oil pan, to spread the load. I do not recommend lifting it by the balancer ring. I also had to carefully move a power steering hose over just a bit so as not to pinch it between the floor jack/block of wood and the oil pan! I also removed the motor mount brackets from each side of the engine block, otherwise you would have to jack the engine up way too high to clear the vertical engine mount “stud”, risking damage or crushing something against the firewall etc. and it only took a few more minutes to remove them. Yes they were kind of a pain, especially the driver side, but nothing I couldn’t handle. By removing these brackets, you only have to jack it up a few inches to gain a little more clearance. Just take your time and use common sense to not damage anything by lifting it too high.

She is very happy with her Mustang now, and she said that it’s so nice to be able to drive it and it doesn’t shake the dashboard every time she’s at a stoplight or pulling into the driveway. I’m glad I did the original oem throttlebody and spark plugs and wires anyway as we didn’t know for sure how old the tuneup parts were and the throttlebody seems to have improved its drivability and power.

The transmission and fluid are fine, I felt very certain that they were not the issue from the start. But thank you for the input, and now I have to get back out in the barn and get back to work on my ‘68 Mustang!