I’m the original owner of a 2005 Mariner (3.0L V-6, 114K miles). We live in Central TX, so we are just starting to experience cooler weather (40’s - 50’s at night, 60’s - 70’s daytime). At this time of year and through the winter, this Mariner develops an annoying rough idle. It is more like a strong vibration when in Drive or Reverse, not really a miss in the engine. Increasing the idle speed with the accelerator pedal helps, and it does get somewhat better as the engine gets to normal operating temp, however if the day is cold (30’s or 40’s) it doesn’t get better.
I’ve changed the plugs, changed the IAC valve, and cleaned the MAF sensor a couple of times, with no improvement. We almost exclusively use Exxon or Chevron gas, which should have good fuel-injector cleaning additives, so I sort of doubt the injectors are at fault. I’ve had a local mechanic check to see if any codes exist, but nothing shows up. This has gone on for 2 or 3 years, but it was not like this when the car was newer.
knfenimore, the plugs were replaced with identical Motorcraft plugs. Made no difference in how it runs. Have not ohm-checked the coils - can you give me more info on that? Is there a way to verify the correct operation of the O2 sensors?
jesmed, if I had broken mounts, it doesn’t seem that the vibration would be ambient-temperature-dependent, which it definitely is.
@traktor, rubber’s mechanical properties change with temp, which is why I thought motor mounts might behave differently at different temps. May be a long shot, but not hard to check.
Above posts good ideas. This is a tough one, as it could be caused by lots of things. A mechanic, after doing a general visual inspection for everything connected correctly, and verifying all the routine maintenance is up to date, would check each drivability sensor and actuator one by one.
If this were my car, my first suspicion would be an air leak allowing unmetered air into the engine. Affects the air/fuel mixture, and the symptom is usually worse at idle. (Edit: And worse when engine is cold.) Could easily produce a vibration sensation to the driver. A vacuum leak would be the most likely. Ask your mechanic check for places where a vacuum hose might have been burned by an exhaust component, or a hose that is split at where it connects to a vacuum port. And each vacuum- controlled or vacuum-powered device (brake booster, egr, etc) should be verified to hold vacuum using a hand operated vacuum pump device.
GeorgeSanJose, thanks, those are excellent suggestions. Honestly, I had not considered a vacuum leak as a possible cause, but I’ll definitely check that out. (I’m the mechanic on this vehicle, for better or worse. )
Our 2010 Mariner got rear-ended at a traffic light last week. Damage seemed limited to rear bumper BUT since then car is vbrating badly at stop lights and other times when stopped in gear. Appraiser thinks the guy was going 15 mph but braking on impact. Is my car just nervous? Or is it likely to be motor mounts?
@PT Jimbo, “vibrating badly when stopped in gear” does sound like more than the bumper was damaged. Have someone put it on a lift and check motor mounts, exhaust system, etc.
PT Jimbo, I’ve been in a situation like this. At least in my state, regardless of whether the damage is to the body or to the mechanical portions of the car, the insurance co. is obligated to repair it. The normal way to approach this is to select a reputable body shop, make sure they know about the problem in advance, and have them deal with it, which will mean they need to send it to a dealer or other competent repair shop and have the problem diagnosed. Body shop pays for the repairs and the insurance co. reimburses the body shop. The body shop I deal with has a “lifetime warranty” on the repairs they do, including any subcontracted work like this.
Much easier that way than you having to argue directly w/ the insurance co. about whether or not they should pay for it. Of course, in either case, the success of the claim is dependent on the cooperation of the insurance co., but having a good body shop on your side is a big help.
knfenimore, thanks much for this link - the instructions are very well written. Made me recall that there WAS some oil in the front plug wells when I changed plugs but it didn’t occur to me that it could cause a misfire (duh. . . ). I’ve also noticed some oil seepage getting onto the exhaust pipe, so it is probably coming from the cam cover gaskets. I have a project ahead of me!
I did put in new upper manifold gaskets when I replaced the plugs, but that didn’t seem to make a diff, so probably I did not have a vacuum leak there.
Having the exact same problem with my 2005 Marnier 108k original owner in NY. Rough idle and noisy vibration. Gas mileage has dropped a bit. Plugs where changed. Cleaned the IAF, changed the fuel filter, put fuel injector additives and MAF looks clean. Scan tool not showing any fault codes.
I do get some fluctuations of idle speed but nothing major (700-800 rpm range). Have not yet checked vacuum leak.
Jimbo, I realize you’re new to the forum, but hijacking someone else’s thread diverts attention from their problem, adds to their thread unrelated answers, makes if difficult for those of us trying to help to keep the answers straight with the questions, and generally messes the thread up. We’d love to help you, but please start your own thread. If you need help doing that, we can offer instructions.
WAIT A MINUTE: I just realized this thread is actually 4 years old. Mtb 2018, you might get better help if you started your own thread. Making an old thread even longer only confuses things, and in all likelihood your problem will have a different cause.
The problem with the Mariner (just recently given a new home, 148K mi,
and running great) turned out to be a broken motor mount. This motor
mount is the one located on the passenger side inner fenderwell, and is
relatively easy to change.
The way I diagnosed it, per a suggestion from a professional wrench I
know, was to put a 2 x 8 piece flat on top of my floor jack, then place
it under the oil pan and slightly elevate the engine. You then start the
engine and see if the vibration still exists. If it goes away, replace
the motor mount.
Good luck, I hope your solution is as easy as this!
Neal - Thanks so much for the response!! I will certainly try your suggestion to see if it is indeed the motor mount. That would make my life easy…Will post something once I do the test.
@traktor Yes the issue was the hydraulic motor mount! When I removed the old mount you could see where the hydraulic fluid leaked out. Replaced and started it up with no more rattling and vibration. So quite!
For those of you that may have the issue. I went with “Genuine Ford 6L8Z-6068-AA Engine Support Insulator Assembly” that I found on Amazon for $76 (that fits 2005 Mercury Mariner V6 3L). You will need some long socket extensions and for me an 18mm and 15mm sockets. Took about an hour…
Mitch, glad this worked out for you! I chased that issue for a couple of
years before I solved it. I also had heard a “clunk” when accelerating
from a stop light and I’d have bet money it was coming from the rear.
Replaced several components in the rear suspension w/o any improvement,
but when the motor mount was fixed, no more clunk!
Neal
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