Shaky idle only when on drive/brake MAF or no?

[DynoXG]

I've read extensively in the forum that the MAF can cause idle issues. I have no check engine light on and no error codes. I already cleaned the sensor with CRC MAF cleaner.

Here is my question, if the MAF is the problem, would it also have a rough idle when the car is in neutral or park? My car shakes like Shakira's booty when I'm at a stoplight, but if I put it in neutral or park, it's super smoooooth and no shaking. Is it the MAF?

It's embarrasing when I give someone a ride and it feels like my car is giving you massage at a stoplight. :embarr:

[c55m8o]

There can be so many different symptoms of a bad MAF I'm not going to say it is or it isn't based on my experience compared to yours. For me, it was rough (and eventually stalling) both in gear and out. But again, don't let that negate the MAF being it for you.

It could also be the engine or tranni mount. I'll ask, when you accelerate from stop or drive up a hill when starting from a slow speed @ the bottom, do you hear a 'kunk' sound from in front of you, and/or feel something knocking @ your feet? If so, that's the engine mount.

[DynoXG]

Thanks for the reply. There is knocking noise. I thought it might be a motor or transmission mount as well since my friend had a similar issue with his bmw after he launched it a couple of inches and the car went airborne. He broke his motor mount. But I checked and mine are ok.

[c55m8o]

Originally posted by DynoXG
But I checked and mine are ok. You sure? Maybe you're a tech and know for sure; dunno. If there's a knock, it's a dead give-away to me tho.

[DynoXG]

Yeah, there's no knock. But even though I checked I'm starting to doubt myself. lol. I'll go to a shop later today to have them check 100%.

[c55m8o]

Oh, there is -no- knock. I only replied what I did because you wrote "There is knocking noise" the 1st time... ;)
Originally posted by DynoXG
Thanks for the reply. There is knocking noise. I thought it might be a motor or transmission mount as well since ...

[DynoXG]

Oh my gosh, you're right. I left out the no. Either way, i'm gonna have it checked. It's something that get's really annoying. Especially when I go home and I get stuck in traffic, all I have is the shake.

[jnenad16]

is the ac on when the shaking happens?

nenad

[DynoXG]

No, I hardly ever use the AC. I've been reading old articles in the forum and I think i've narrowed it down to two things. Either the motor mounts like c55m8o said, or a vacuum leak.

I think it may be the vacuum leak causing the shaking. When I turn on the car, I can hear the vacuum pump make noise for about 1 minute and then it stops. It sounds just like an electrical antenna going on and off every few seconds, it makes a motor sound on and off for a while when I turn on the car and then it stops. So I will search the car for a leak and if I don't find one, I will consider changing the actual vacuum pump.

The one I'm referring to is in the trunk, when you remove the side paneling on the right, and it's covered in black foam. This is the one making noise, and from the old posts, it might be the cause of the shaking. Thanks for your replies guys.

[jnenad16]

the vacuum pump you are referring to is for the central locks and few other things, has nothing to do with the engine. you would need to inspect all the vacuum lines in the engine compartment, while paying extra attention to the throttle body vacuum lines, which are the least noticeable (and often overlooked) culprits of vacuum related rough idle.

nenad

[First Benz]

What engine?

[Nelson Lago]

didnt you post this allready

[DynoXG]

Ok. Thanks c55m8o. I'll have to check all the vacuum lines individually. The shop yesterday said the motor mounts looked ok, but said that due to the age I should consider replacing them. I'll go ahead and do that, and afterwards if the problem continues I will troubleshoot the vacuum lines.

Engine is a 2.2 v4.
I hadn't posted this before.

When I resolve the issue I'll come back and post what it was so others can fix a similar common issue.

[First Benz]

Well first off, it's not a V4, it's an inline motor. :)

Secondly, take a look at your plugs, I'm willing to put money on the fact that most likely #3 or #4 [the back ones] is carbon tracked. Check all of them, but those are the ones that are very common.

It's also very common with that problem to only show up under load. In park, there is no load on the engine, so they fire properly. As soon as there is a load present, even as little as from it being put in gear, it'll start to miss.

Check those BEFORE you replace your motor mounts. Sure, due to age it wouldn't hurt to do them, but that won't fix your problem.

Eric

[livin503]

shit i am having the same issue, my acceleration has dramitically decreased and will sometimes knock when i accelerate it, i also do get that shaking when my car is in drive, but not when in neutral or park, its very frusterating. sometimes when it shakes ill turn my car off and restart it and the shaking will go away. also ill be on the freeway driving like 80mph and it will start shaking and the motor will almost sould like misfiring, but when i stopped there is deffinantly a burning smell... i think i got a whole situation of problems, any help would be very very appreciated! im going to go get a new fuel filter and check my plugs and wires, but im just kinda blindly guessing the problem

any suggestions?

[Green Lantern]

i had the same problem but i brought it to a mechanic for a full tune up and now its gone. but the best thing to do is pull over to the side then turn off the engine and then crank it over again, after u restart the engine the shaking dissipates.

[First Benz]

The reason the misfire is gone when you cycle the key is as follows: :)

Once the ME control unit senses a misfire enough times. It shuts off the fuel to whatever cyl is missing, so it won't damage the cat by dumping raw fuel into it. When you cycle the key, while the fault is still recorded, it gives the engine a 'clean slate', and it starts watching for misfires again.

For some reason, moisture acumulates in both #3 and #4 plug holes, primarily #3, and it causes carbon tracking, and the missing.

BUT, that's only on the I4's. The 6's and 8's have platinum plugs, and due to their angle, moisture doesn't accumulate by them.

Eric

[livin503]

so what would be the cause of this misfiring? is there a specific part i could fix myself to stop this? if i replace the plugs ad wires should this help solve the problem?

[cocawhitebenz]

First thing is check those Spark Plug Wires. I had the same problem a few weeks ago. WIRES!!

[First Benz]

While the wires could be a slight factor, the plugs are more likely. But before you go and just start replacing parts, pull the plugs out and check for carbon tracking. It's extremly noticable if it's there. Little black streaks often times all around the plug, and sometimes, it it's really bad in one spot, it'll be a huge black mark in one area.

And the 4 cyls don't really have plug "wires" per say. They have two plug "ends" that go right onto the plugs from the coils, and two wires that go to the other plugs. However, you can unscrew the ends from the 2 wires as well. So all you do is just replace the ends, as that is what ends up going bad.

The only time I'll replace the plug ends is if the very tip of them is brittle and crumbles off when you try to flex it. The should be very soft and supple to the touch. But even if they are brittle, that most likley won't cause a misfire. Mine look like hell and I'm just too lazy to change them, and I don't have a miss.

So yea, pull the plugs and look at them. That's easy enough to do yourself. :)

[livin503]

would fuel filter have anything to do with this?

[First Benz]

Anything and everything is always possible. ;)

But the fuel filter? Not likely.

How many miles on your car?

[livin503]

160,ooo ;)

[First Benz]

How long have you had it and have you put a filter on? Benz recommends them every 60k.