mchang18

Hey guys,
I'm in need of some help. My 97 C36 idles violently when I'm coming to a stop after the car has been warmed up.

I cleaned the throttle body, I checked the motor mounts and it isn't misfiring so I doubt it's the spark plugs. Could it be the MAFS? What else would cause this?

No loss of power as far as I can tell. I have to put it in neutral at every stop because it is unbearable.

Any help would be greatly appreciated!

PS My Air intake tube that goes over the block is a bit beat up so I called my local 3 point motor store and they quoted 1,700$!? I was shocked.

Sulaco

Oil leaking into the chambers? Pull your plugs and look for oil on them. Also check intake air temp sensor.

cm60k

Before spending $$$$, try to diagnose the car first, FAULTY codes will tell...

ZAYED,,

mchang18

I'll check the plugs and intake sensor.
The car isn't showing a check engine light so it is tricky to diagnose.

Super B

First place I'd look is coils. I'd wager one of them has cracked in the tower and is leaking spark common failure if they're original square flat top coils.

Super B

Also unplug then re plug the injectors one by one at idle and see what cylinders are mis firing. Kind of narrow it down. This will throw a bunch of codes but they will clear after a few cycles.

PJmak

Would this also be a good method to help identify which valve lifters need adjusting/replacing if one is getting knocking from the engine...

Super B

Look for this on the coils.

RPB

Good place to start.

mchang18

Spark plugs were worn, and the spark plug wires were torn and arcing. replaced both. Even though there was no check engine light it had 4 codes 2 of which were miss fires on the 2nd cylinder. (check engine light bulb may be blown) One was an O2 sensor the other was a fuel gauge malfunction. I was hoping I resolved the issue but after an hour of driving the issue had returned.

I didn't replace the O2 sensor because I figured maybe the other issues triggered that code. Would a faulty O2 sensor cause surging?

I will take a look for any cracking. Thanks Super B.

cm60k

Ohh, i heat o2 sensors when damaged,

surge & performance are the main sacrifice things when o2 sensors shouting....

ZAYED,,

RPB

I feel bad for you, it sounds like you have been through quite a bit since you have owned the car!

Did you drive it or have it inspected prior to purchase?

mchang18

Drove it but not inspected. It was a weekend and out of town. I inspected as best I could but the issue happened about a month after I bought it. It is a used car that is 17 years old. It's not perfect. I enjoy driving it and if it gets to pricey I will have to sell it. At only 130,000 kms It has a lot of value.

RPB

Yeah our cars are getting on, my C36 is about to be 20 yrs old. The main thing is you enjoy driving it! The one thing you might want to check that no one has mentioned is the throttle actuator, if you have already verified the coils are not the culprit. This plays a big part when it comes to idle control, I would recommend giving it a good clean if it's not operating properly. This went bad on my 500E and caused erratic idling and surging. Take your time and be careful when cleaning it! GL!

DRBC43AMG

If the engine has only done that distance, it is just run in. The rest of the vehicle should also reflect this figure, providing that the counter hasn't been rejuvenated. OK, some rubber parts and wires may perish at that age even if the vehicle is not driven.

mchang18

Found the problem. Unfortunately it's the plastic air intake tube that goes over the block. The one that says, "3.6" on it. I blew some smoke around and noticed it has a crack on the underside of it. I'm guessing they are near impossible to find used and I am definitely not paying 1,700$ at 3 point. I could jerry rig something but god knows how it will look. Anybody have a solution or know a wrecker who might have one?
Thanks for all the advice!

RPB

I think the regular w202 crossover might work. Hopefully others will chime in to confirm whether or not it will. GL!

Sulaco

Yes, a regular C280 crossover pipe will work just fine. Only difference is the flatter radius of the tube and the "3.6" on the AMG model.

Otherwise you could epoxy the crack? Simple, cheap, effective.

mchang18

Spoke to my friend the plastic welder. he said it's an easy fix. I put a piece of tape over the hole/crack and so far it hasn't acted up once. I suppose it could be worse right?

Thanks for all the help guys. I'll update once I've completed the work.