Rough Idle in Drive

[BBad199]

Within the last 2 months, I've noticed my car start to idle poorly when the brake is applied and the car is in drive. The entire cabin begins to basically resonate and it gets pretty loud. The car idles at about 550 RPMs while in drive, but when I put it in neutral or park, it runs perfectly normal as it used to at about 700 RPMs.

98' c280 with about 94k

I assumed that I just needed new plugs and replaced them with OEM Bosch single electrode plugs. Still having issues with it. I also had my buddy remap my fuel settings, but that didn't seem to do anything either.

It seems to be getting worse, so I'd like to get it fixed before winter. I haven't had any trouble with it dieing when I finally hit the gas, but it seems tp sputter a little before it really kicks in.

Any ideas on what could cause this? Thanks!

[BALLLR]

i think i may have the same symptons as well. most notable when the brake is applied.

[DynoXG]

I'm not sure about the sputter, but you may want to get your motor mounts checked.

[BBad199]

Can someone explain to me how I can recognize bad or worn motor mounts? I would like to check into this problem. I recall being told they aren't that bad, but I don't remember how long ago.

[DynoXG]

This will help (http://www.club202.com/forums/showthread.php?s=&threadid=12637)

[BBad199]

I read through the responses, but I don't think my issue is motor mounts. The reason why is the vibration tends to be worse when it's cold, and almost completely go away once the car is warmed up. If the mounts were bad, then it would do it all the time.

What does the engine being warm have in common with a rough idle while in drive, but not neutral or park?

I've read every thread pertaining to vibration and am still looking for answers.

Jonathan

[DynoXG]

I dare to differ.

Check this thread out. (http://www.club202.com/forums/showthread.php?s=&threadid=6116)

This shows that after warm up the problem can go away. I had this same problem solved by the replacing the mounts. Like I said, it may not be %100 the problem, but it is the most likely.

[BBad199]

Thanks for the help! Ha. I read that thread earlier but didn't finish it after Greenphant posted:

"If the vibration goes away, it doesn't sound like motor mounts. If the mounts are bad, the car will always vibrate when at idle, and more so when in drive at idle."

I didn't keep reading...sounds like an excellent explanation near the end. I'm going to suggest it to my mechanic and see what he says. I've heard a million and one different solutions. I want to be certain I will apply the fight fix.

Jonathan

[BBad199]

I'm going to just replace them myself when I have the time in the next week.

Can someone tell me if the Corteco brand is a good replacement? If you would recommend another brand, please let me know. I don't want to install poor quality mounts.

Jonathan

[DynoXG]

Remember to check with your mechanic to get his opinion about the problem. Also remember to make sure you have enough time to do it. I didn't change them myself, but my mechanic took 3 1/2 hours to do the job. Remember to post if it fixed your problem for others who search the forum.

[xvvvz]

>>but my mechanic took 3 1/2 hours <<

Isn't that a book-rate quote for time though? At first I thought you meant just one mount. Did you mean all of them? I bet it still didn't take 3.5 hours in reality.

[BBad199]

I got a quote from a local goodyear for $260...that's if I brought the parts with, but I couldn't tell if the kid who answered the phone was confused or not. That was 3 hours of labor included.

I'm going to have to build myself ramps. The ones I have won't clear my front bumper...(what a pain).

Does anyone have a decent "how to" guide for a w202? I would assume that the car sitting on the incline of the ramps won't cause any problems when I lift the engine from the oil pan. In other words, it's going to go straight up and won't shift after I remove the old mounts. This way there isn't a hassle trying to make sure the new mounts sit where the old ones were.

Any help would be greatly appreciated!

[DynoXG]

Originally posted by xvvvz
Isn't that a book-rate quote for time though? [/B]

Not sure. Maybe my mechanic took longer because he doesn't do too many Mercedes. But I don't care because he charged me $120 for the install and did a great job. I bought both german mounts on ebay for $90 shipped.

As far as the how-to BBad199, a member here "Oberoi" has a great W202 book. You may want to cantact him and see if he's willing to take pictures of the how-to and post them up here. It's a Hayes manual for the diesel 202, but the mounts should be the same.

[BBad199]

Just so that everyone knows, I spent an hour on the phone trying to figure out what P/N that the dealerships are putting in these days...

They've changed manufacturers about 100 times, and the latest and greatest number is 203-240-0517-98. The -98 isn't a type-o, they made a new version of the old part. I've found them as cheap as $100 each from the dealership at retail. Also, be careful not to get 202-240-2817 because they are for inline 4s.

This is for a 98' C280.

Jonathan

[BBad199]

Last Thursday I had a chance to put the new engine mounts in. I put Corteco/Freudenburg mounts in (got them for $110 to my door off ebay) and everything seems to run great.

The install was not simple, but not super difficult. We all know there isn't a lot of room to work in a mercedes, but this job took several hours to do for me. First off, I advise doing it on a lift. I had several problems trying to physically get enough space to remove the driver's side mount because the steering linkage was in the way. There just wasn't enough room even with the engine jacked all the way to the tranny firewall. I had to unmount a breakline and a heat sheild on the driver's side to get the mount out, on top of having to disconnect the air box to get enough engine height and the engine to frame ground wire. The passenger side mount was easy to remove because the AC compressor isn't in the way like the driver's side. You can slip this one out toward the front of the car. Also, there is a heat shield you will need to remove on the passenger's side, and absolutely no way to possibly get to the top side bolt but from the bottom. That means there is almost no room to turn a wrench and you are doing the turning blind. Beware of the starter! I had a wrench slip and break off the positive wire cover which gave me a quick firework show and scared the crap out of me. I advise you get a 16mm stubby wrench for the top side bolts. Also, the driver's side top side bolt is hard to get to. I was able to get at this one from the top by removing the washer resevior to make it easier, however this is not necessary.

Were the mounts the problem? Absolutely. They were both cracked and leaking fluid. Things are nice and smooth now.

Would I do this job again? Absolultety. Really wasn't too difficult. Just had to improvise things a little bit when I ran into problems. Still saved $270 labor for having someone else do it.

Sorry, no pics. If you are looking at doing this one yourself and have any specific questions, post em up and I'll do what I can to answer them. So that you know, my car new shocks and springs which equate to a 1" lowering. I did it on homemade wood ramps. If you are doing it on ramps, my guess is you will need a jack that will give you at least 8" of lift. Just remember that the first 2-4" will probably just be taking the weight off the suspension as you are lifting the engine. There is nothing that binds the engine to the frame but the mounts.

[DynoXG]

That's great BBad199. I'm glad you found the problem without having to shell out a lot of money on other things and finding out later that they weren't the problem.

As for me, I still have a little bit of a rough idle. The shaking significantly went away after changing the mounts, but I still get a little vibration, so I guess the MAF will probably be next to change since my car has 211,000 miles and it's never been changed.

Glad to hear your car is good again and thanks for posting resolution.

[202rules]

Originally posted by DynoXG
That's great BBad199. I'm glad you found the problem without having to shell out a lot of money on other things and finding out later that they weren't the problem.

As for me, I still have a little bit of a rough idle. The shaking significantly went away after changing the mounts, but I still get a little vibration, so I guess the MAF will probably be next to change since my car has 211,000 miles and it's never been changed.

Glad to hear your car is good again and thanks for posting resolution.

I just fixed a really bad case of misfiring in my car which does manifest itself pretty noticably during idle while on D. My problem turned out to be the point of contact between the main wiring harness and the three coils on cylinder 2, 4 and 6 (mine is an inline 2.8). I was able to create more contact between the plug on the cable end and the coil by using a screw driver to pull out a little what I think were the ground leads on the cable end. They looked like three small plates that stuck in tangent to the core of the plug, I wish I had taken a picture of them. Anyway, I figured this out when I noticed that just by poking those plugs when the car was running and the cover was off, the misfire came on really bad. so you might wanna check them out.

[DynoXG]

Thanks 202rules. i'll check that this weekend :)

[Cru328prod]

wtf...........i changed both motor mounts and have the same problem, i have a CEL for a fuel trim malifuction....

[DynoXG]

Changing the mounts will not resolve a CEL. A fuel trim malfunction is more difficult to troubleshoot. You may want to find a good mechanic's opinion on that issue. Or maybe some other members here may have some input on it.

[Cru328prod]

hahaha everyone says

o2 sensor or MAF......i've change the MAF......i don't think its the o2 sensor but i'll try to get it....i figured it wouldn't be a motor mount......but after reading everything i was like wtf how soooo

[DynoXG]

Hey Cru, you wont believe this. After I went home from work and reading your post my CEL came on. And here's the weird part, I got a P0170 "Fuel Trim Malfunction" just like yours. I erased it twice and both times is came right back. Anyway, I put in my old MAF that I had changed before during routine maintenance, erased the CEL, and it fixed the problem.

I know you already changed your MAF though. Did you buy an exact Bosch replacement for you model?

[Cru328prod]

haha i don't know.....it didn't say bosh on it.......i bought it on ebay

[DynoXG]

That's your problem then 99%. I bought a new one on ebay for $99 shipped a while back and it didn't even work. It was like I threw my money away. The seller didn't want to exchange or return my money. I think that may be your problem.

[Cru328prod]

lmao man its been not stop money spending on my car, and the shitty thing is..im to blame.......im going to by a mustang since i work for ford..........cost plus 20% sounds so much better then 20% below retail