I was driving to work, and about 10 minutes into the drive, (15 min drive total), a smell came out while I had the heat on. It was a burning / propane-ish smell. Not very strong, but I knew it was there. Then, 10 hours later on my way home the heat was one and 2 minutes into the drive it started again. I turned the heat off and it went away.

Anyone have any suggestions as to what it could be?

 

Did it smell kind of sweet at all? May be leaking heater core?

 

What could I check for if that is the issue other than the smell? It was a faint burnt smell, propane like smell.

 

Perhaps the catalytic converter of a car in front of you? When you turn on heat is it pulling air from outside of car versus just circulating air inside? Just thoughts not sure which way it works and too lazy to walk outside and look!

 

could possibly be that oil is running out from your valve cover and dripping onto the exhaust/header. Happened to me had to replace the gasket on the left side of the motor, but i also had done extensive motor work done to mine so it dripping from the valve cover onto the exhaust was mostly my fault, but i'd still check tho, or possibly when adding oil to your car did any of it accidentally drip onto the motor?

 

+10, had the same smell/problems, replaced valve covers, still had smell, just recently found out it was transmission fluid coming out of the breather tube, burning on its way down the side of transmission. so i would check the valve covers first, then the breather tube on top of the transmission. good luck.

 

Ok, so not only is the smell coming, but its affecting the way the car drives. (Not the smell, obviosuly, but whatever is causing the smell.
Its 'slowing' my car down. Well not really. But, when I shift, and push the gas pedal, it climbs the rpms very slowly, then jumps and gets going. Something is stopping me from driving smoothly. Its very hard to explain.
Its almost as if I start to drive, and someone is holding my car, and then lets go and I get going. Its like a delay in every gear. And the smell is coming out of the engine, and front wheels. I am clueless.

 

it sounds like you have not even taken the time to get a flashlight and inspect the engine and transmission for leaks.

 

Oh, no I have. Looked at everything under the hood, under the car, etc. Please dont assume things I did or didnt do.

Update: After putting the car into 6th gear, I gradually picked up speed. I went from about 40 or so to about 50-55 and the whole time, the revs went from 3k to 3500, then back to 3k then they started going up to like 3800, then back down. Never did the revs go past 4k. Usually, if im gaining speed, the revs will climb gradually (like another other car), but they stayed in that range.
Also, the cluth feels a lot softer. (I THINK) The Z is known for its tough clutch, right? I thought the same when I first drove it. It was hard to depress. Now, its soft, and feels like a whole different car.

 

Burnt clutch? *shrug*

 

could be clutch fluid leaking from the slave cylinder inside the transmition and getting to the clutch/flywheel and burning up? Not sure if that's even possible. That would make your acceleration change if your clutch fluid got low (check that) and there's oil on the clutch itself. My old '84 Z had an external slave cylinder that I had to replace 2 or 3 times due to leakage lol. Just a thought.