Hey all,

I have had a problem w/ my engine stuttering upon acceleration, accompanied by a slight backfire-like noise (not a true backfire).

I researced the forum and found some threads attributing this type of problem to a bad catalytic- so I had it checked out. Nothing wrong w/ the cat - the problem was still occurring w/ the cat removed. I had a head gasket job about a year ago - my mechanic thought that perhaps a slight adjustment of the timing chain would remedy it - no solution. The MB computer doesn't detect any problem with the car! Somebody please help before I spend a couple 1000 on just trying to find the problem and then a couple more trying to fix it!!

The car has about 210k miles on it...all but 40k are mine.

Thanks
Panicing in SC

 

Replaced the harmonic balancer yet?

Took out the catalytic converter?? That is a crime bigger than molesting a child. Where do you live?

 

No, I haven't replaced the harmonic balancer, but do you really think it relates to stuttering and acceleration probs?

We put the Cat back on after determining that it was in good shape. We considered removing it permanently since I live in South Carolina (no emissions) and I would never sell it out of state, but I believed it was better (for a myriad of reasons) to put it back on.

Thanks for the reply.

 

Removing the cats would cause continual problems unless you installed simulated O2 sensors. O2 sims aren't particulary expensive or difficult to install, but you'd be giving up fine tuning of the air/fuel mix by the ECU and causing more air pollution than necessary.

Could it be a bad tank of gas? If it just started it could be a bad tank you recently bought or condensation that formed overnight. A can of gas treatment would remedy this.

You could have a dirty MAF sensor. Clean carefully if necessary.

Check the air filter(s). Make sure they aren't clogged or wet.

Maybe the head gasket job was less than ideal? Any smoke coming out of the exhaust? If so, what color? Any oil in the coolant? Look for mini oil slicks in the overflow tank. Any coolant in the oil?

 

LOL. Thanks for not getting mad. I was just kidding about the cat removal.

Try to get a new harmonic balancer. Parts and Labor are FREE at the dealer for harmonic balancer.

But for stuttering...I think there are 2 possibilities.

(1) Something is not right with the head job. Were the valves disturbed somehow?

(2) A good chance...one of the plugs is not snugly in touch with the coil packs. Double-check on that. Make sure all the plugs are equally worn out. If one is wet or seems too new, you know that assembly has issues; maybe the contact, maybe the coil pack, maybe the wire.

 

Head gasket job was solid. No problems w/ filter. Nothing but green goodness in the coolant. No smoke. The problem started about 6 months ago but was only noticable upon hard acceleration. I took it easy, used cruise often, and it was ok. I knew something bad was looming, though. It increased as the weather turned colder, so it's not a bad gas issue (although the feeling I get in the accelerator is reminiscent of a bad gas type problem). MAF is something I need to check out.

 

FLY:
I think both the items you mentioned would trip the computer. We're getting no problems detected, so we're trying to track it down elsewhere. Harmonic should be done regardless, but how do you think it relates to my current dilemma? Thanks...

 

the backfire is in intake or exhaust side?

if from the intake, it's air mass sensor.

if exhaust, ignition or mechanical timing.

 

My 94 is doing the same thing... taking it to the dealer in the AM... Tech told me plugs or MAF... push on the gas and put a load on the engine ( power break it) if it misses the Tech told me PLUGS.. if not MAF... most likly..

they aren't cheap, some make sure.... I onlyhave 125k on mine....

I will keep you posted after the ck up..

 

The mystery grows...
Replaced MAF - NOT IT.
Replaced coils - NOT IT.
Checked throttle - NOT IT.

The problem shows around 2300 rpm. Even when the problem is occuring the computer reads NOTHING.
I'm running out of areas to check. My mechanic and I are pulling our remaining hairs out! Could my computer be shot?
Can it be replaced with a used computer and reprogrammed? I'm afraid this is the C280 Titanic....