Aid!!! Problems with my jetta 94

Hello, I'm having several problems with my 1994 Volkswagen Jetta, manual transmission, 1.8L engine.

1. The car starts fine, but if I let off the gas, it stalls.
2. The engine sounds muffled and backfires slightly, nothing loud. It jerks a bit at low speeds, usually in 1st and 2nd gear.
3. It seems like spark plug number 2 (if you look at the engine after lifting the hood, it's the second spark plug) isn't working. The spark plugs aren't getting wet with oil.
4. There's a little blue smoke in idle or neutral when I'm stopped at a light and when starting from a stop.
Here's what I've done:

1. I changed the spark plugs, wires, distributor cap, and rotor... Everything is new, and the problem persists.
2. After I changed the oil and filters, the smoke started.
3. The timing was recently checked.

Some friends (who supposedly know their stuff) tell me:
One of the spark plugs isn't working.
Check the engine compression, because that's why it's losing power.

Can you help me? I don't go to the mechanics around here because they're not honest; they just want to rip me off. That's happened to me before.

Thanks for your comments.

Betobrambi,

Manzanillo, Mexico

If the smoke occurs when starting the vehicle, then the problem might be with the valve stem seals. Measuring the compression is necessary because of the backfires; there could be a burnt valve. The power issue is related to the same thing. Do a simple test: with the engine idling, disconnect the spark plug wires, starting with the first one, and see if the engine runs worse or stays the same. This will help us know what to look for and where.

Question: Did you change the ignition coil too? Although it might improve things, I'm not saying that's the problem. Backfires are almost always due to burnt valves. Do you have headers or a performance exhaust? That can affect them.

I'm going to change the ignition coil. It has a standard exhaust; I don't know what headers are, but it's nothing sporty.

I was told the valves might be burnt, but how can I check this?

Thanks for the advice.