Burning smell -》eventual ecu failure

Hi everyone, I've a 2000MY 996 C2 with the 3.4l engine and 100k on the clock. I started noticing a burning smell after hard driving, but it dissapeared within seconds. The consensus from posts here was that it was common and nothing to worry about, ans I took it to my local specilist and they just said to bring it back if it gets worse. I was going down the motorway when the engine and dashboard died suddenly, gliding to a stop in the outside lane of a busy 3 lane motorway is scary stuff. The specialist said it was the cam shaft sensor which had burnt out and caused the ecu to die due to some blown fuse. Replacing the sensor involved removing the engine and wasn't cheap. I got the car back 2 weeks ago but hadn't used it properly, until tonight. The burning smell is still there, the engine sounds 'lumpy' idling, and the 'check engine emissions' light flashed for 10 seconds on two different occasions over the 40 min drive. I'd welcome any suggestions on what might be going on. I'm hesitant to take it back to the same garage if it's the same problem I paid them a grand to fix already.

I'd take it back and let them know their work was incomplete.

Sounds like they may have left a spark plug/coil wire disconnected causing a misfire on one cylinder.

Quotes source post: 13823522

A burning smell is not normal. Well, not normal except in very very rare cases. For instance, once in a great while I'll catch a whiff of a burning smell from my Boxster. I've never caught the burning -- so to speak -- in the act but one time I had the engine exposed and spotted a charred piece of plastic wrap, like a pack of cigarettes is wrapped in, on top of the engine among the intake runners. I suspect this plastic had been blown up and contacted the hot exhaust then charred and come loose to end up on top of the engine. I believe it is something like this that accounts for as I said above the very very rare times I smell just a hint of burning. And I've never caught more than a whiff just enough to to know I didn't imagine it but no more than that. OTOH, a mix/combination of odors of hot oil, hot metal (brakes, exhaust), hot tires is normal. Just wanted to get that out there. My advice would be the same as 808Bill's. Take the car back. Hate to sound like I'm picking on you but I have to stress how important it is when picking up a car after any work to assume you will find something wrong and have to leave the car. If you had the oil/filter service done as soon as you can check the oil level. Give the car a walk around for any leak sign, any damage, and that everything looks ok. If you had the cooling system touched check the coolant level. Be sure the special security wheel stud socket is present if you use security wheel studs. And so on. After your inspection/walk around you have to give the car a decent shakedown test/drive. Nothing fancy but try to use the car in such a way to at least see if you can reproduce the symptom/behavior that prompted you to bring the car in in the place. If you find anything amiss take the car back then and there. If you take the car with a known problem you signal you are willing to accept subpar work.

^^x2...I've learned that the mechanics make the same mistakes I've made. I never pay them until I check everything, then take it for a long test drive and recheck.

Quotes source post: 13823522

It appears you paid them a grand to not fix it. A) Car runs great but smells hot sometimes. B) Car craps out completely. C) Shop performs repairs; repaired car does not run right. D) Car smells hot sometimes. I'm going to go out on a limb and say that you should operate under the assumption that A and D are unrelated to B and C. For you to get satisfaction from the garage, you need to concentrate only on B and C, since that's what you paid them for. Introducing the burning smell into the narrative with your mechanic is going to do nothing except give them an excuse that your car's current issues are somehow attributable to an as-yet undiagnosed preexisting condition... Re: the odor - A 16-year-old car is going to collect some amount of road grime, residue from worn tires, seeped fluids, and other crap in places you can't wash off with a garden hose. When you get the car hotter than normal, you are going to burn off stuff that normally doesn't get hot enough to burn off. However, you're the only one who can make any kind of judgment about whether what you're smelling is the smell of a hot engine and hot exhaust or something else.

Find out the codes that caused the check emissions light to come on. If your "specialist" is any good, there should be specific codes/reasons why the engine is not running right, and they should give those to you. This is one case in point on the value of owning Durametric software so you can see for yourself what is going on. Not only will it help troubleshoot the problem(s), you can see real-time values with the engine running to determine what is going on.

I put up a thread last month about how horrible my car smells compared to other 996's my friends own and I got a bunch of replies to not worry about it.... My smells exactly like a burnt tire though (as if you had a blow out) All my fluids are to appropriate level and my car does not drip anything. Garage floor is spotless. I have probably put 3,000 miles on it since the smell started and still don't have any real issues other than the smell. Some say it may be tire debris landing on my exhaust? Not sure

Perhaps the odor relates to riding the clutch a bit -- been there, smelled that!

If the car is being consistently stinky, something is up. My car gets a bit malodorous if I've been ragging it, but it does not smell any worse or different than any other car during normal day-to-day operation. VDub, I'd be inclined to agree that you might have picked up a chunk of tire debris that is somewhere on your exhaust or a heat shield, but it would make me nervous that it never went away. You might want to pull off your serpentine belt and make sure all of the pulleys are turning as expected (and the belt isn't glazed or worn) if you haven't already done so. Coolant and rubber smell alike to many people; it might also be worth verifying that you don't see any indications of coolant weeping from your radiators and associated plumbing...

Hot exhaust pipe picked something up off the road? Had a plastic bag get cought once and it stunk for months no matter how much I (muffler) cleaned it.