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Hey all - my first post here and coming in with a problem I'm hoping can be diagnosed. I've searched through any threads I could find related to RDX rough idle and this one seems different. Sorry for the long post, but wanted to get all the information down.
I have a 2008 RDX Tech AWD with 77k miles. Regularly maintained at the dealership with scheduled maintenance and probably some extra stuff the dealership upsold me on. I live in a hot climate where the summer temps are regularly above 100 degrees and the car will sit out in the sun during the day at work (not sure if that makes any difference).
Timeline:
About 3 weeks before Thanksgiving I started to get a slight rough idle when the car is around the normal 700-800 rpm idle. Can feel it in the steering wheel, seat, shift knob, etc. Around the same time I also noticed I occasionally (usually when cold) got a weird muffled rattle for a half second that sounds like it's coming from in front of me ONLY when first accelerating from a complete stop. The car drives normal when cruising down the road or freeway. Told myself I was too busy to take it in and would do it after Thanksgiving.
A few days before Thanksgiving, I was stopped in a drive thru and the car started shaking pretty bad. I shut off the A/C (it was a warm day), and the car starts squealing and smoke starts coming out from under the hood. Threw the car in reverse and parked real quick. Called Acura roadside assistance and they said don't drive it, sent a tow truck to pick it up, and brought it to the dealership.
Dealership said it was the A/C clutch relay stuck in the on position so they recommended to replace the relay, recharge the A/C system, and replace the A/C relief valve. I did all that and added on spark plugs and transmission fluid (my choice). I get the car back right before Thanksgiving and leave town with the car at the airport.
Come back, start it up and rough idle. Drive it around for a few days and still have the rough idle. I pull the A/C clutch relay out and drive it around and still rough idle. Coworker says to try some Royal Purple fuel cleaner, and I clean out the throttle body / air intake, but neither has any effect. Coworker checks for vacuum leaks and says he can't hear any.
Take it back to the dealership and it sits there for a week and a half around Christmas. Between the service manager and their best mechanic, they said it's probably either a valve adjustment needed or an engine mount. Since the engine isn't shaking really bad and there has never been a CEL, they can't really pinpoint. Dealership says whatever the problem is, it won't leave me stranded on the side of the road which is some comfort. But, it's still quite annoying to have the car shake around when stopped.
Between what everyone has suggested, it's either engine mounts, valve adjustment, or coil packs? Not sure which route to chase at this point. The dealership wants a pretty penny for the engine mount installation. Valve adjustment is reasonable. Haven't asked about coil packs, but I think I could potentially do that myself.
Any other ideas on this one? Do I just need to start doing random replacements until I find the culprit? Appreciate any help anyone can provide.
Valves will tend to make extra noise if they are need adjustment but I can't see how they would make your engine shake. A bad misfire could do that, but that should be something irregular, if that makes sense - it won't misfire on every single engine revolution. If the vibration is more constant and seems to be on pace with the engine rpm, I would start with the mounts. Just my two cents though, and I'm certainly nothing more than a shade tree DIY mechanic. haha
Thank you for the reply. I like your logic on this and am ruling the valves out for now. I will likely go after the engine mounts next unless there's any reason to suspect the ignition coils?
Coils went bad on my wife's Fit a while back, however it was only noticeable at high load/low rpm. Like highway driving, going up a incline type stuff - there the car would mis-fire somewhat frequently. The idle was completely normal. At first I thought the transmission was slipping - luckily the repair was only 200 bucks and 15 minutes of DIY work.
I believe if it was your coils, and they were bad enough to throw off your idle, that your experience while driving would be worse. If you have a few hours on a weekend, take off your intercooler and inspect the coils yourself. When they go bad, it's usually the insulating cover that slips over the spark plug that is cracked. I spotted it on the Fit immediately once I knew what I was looking for.
I ended up replacing the 3 engine mounts and the transmission mount yesterday (finally). The car idles smooth now when the A/C compressor is not on, but when the A/C compressor kicks in, the car has a slight rough idle (although not nearly as bad as before). I can say that overall it's much improved.
Since this whole shake thing was initially attributed to the A/C clutch relay, I'm starting to think the A/C compressor is going? Regardless, now I'm determined to replace the A/C clutch & compressor and see what that does. Probably spending way too much on this car, but really want it to last me a while longer.
The noise / muffled rattle when first accelerating hasn't improved since the engine mounts were replaced. Had my fingers crossed on that one, but no dice.
I know this is any old thread, but can you share how much was the cost for the 3 engine and transmission mounts? Our 2010 RDX mounts are going bad and our mechanic shop suggest to replace them all and quoted us $800 for parts + $200 for labor. Is this repair cost reasonable? Thanks!
I think those are the same on the 2010, but double check.
If you buy them online yourself, you can probably get them for less than $600. Labor for me was close to $400, and I chose to not do it at the dealership. If they will still do the labor for $200 with customer supplied parts, you can probably save a couple hundred bucks?
Posting an update for anyone that comes across this thread down the road:
I haven't given up on figuring this out. Due to the extended warranty on the RDX's A/C compressor clutch (presumably due to a higher than normal failure rate) and my suspicion that the A/C compressor could be related to my rough idle, I replaced the A/C compressor on my car. Of course, I figured why not replace the A/C condenser and receiver drier also, so I did that as well. That was pure hell. For anyone considering doing A/C work, I highly recommend buying the genuine Acura condenser that comes with a genuine Acura receiver drier. I bought an aftermarket UAC branded one and while I was charging the A/C, the desiccant balls shattered and leaked all through the system I had just flushed and added a new compressor to (I could tell because the high and low side pressures went from normal to very odd numbers - low side on a vacuum). That caused my expansion valve to clog so the A/C didn't work at all. I literally bought all new genuine Acura components and did the whole process twice. The A/C works great now though!
The bad news is it didn't affect the rough idle.
I decided to go back to chasing down a possible vacuum leak. Since the only check I ever did on the vacuum was having a co-worker look and listen to the engine, I figured I should probably find a better way. I ran across a hilarious Scotty Kilmer video on YouTube demonstrating the cigar test, which I gave a go. A trip to the smoke shop and a $5.99 cigar later, and I am so glad I did this test! Had a big tear in the air intake hose after the MAF, so the new part is on its way. I got my fingers crossed on this one!
01-07-2016, 04:49 PM
Regardless, now I'm determined to replace the A/C clutch & compressor and see what that does. Probably spending way too much on this car, but really want it to last me a while longer.
