I need help for a Chevrolet Monza

Hello, I'm new to this forum and my question is this: I have a Chevrolet Monza GL that I think was recently rebuilt. I bought it a week ago! The problem is that it doesn't start well, and sometimes it won't start at all. I checked the timing and it's correct, it has spark, and it's getting fuel. If anyone knows what the problem could be, I would greatly appreciate your help. Goodbye, and I look forward to your replies.

Friend, we'll need a little more information to identify the problem. It could be a starting issue, if it's making strange noises. It could be a spark plug problem, if they're very old or black. Or it could be a carburetor or air problem if it's carbureted. If it's a single-point fuel injection system, it could be a problem with too much fuel. Give us more details so we can help you better.

Thanks for answering my question. The vehicle has a single-point injection system, and as I said before, it's properly timed since I checked it again. I recently changed the spark plug wires and the distributor cap, and when I removed the spark plugs, they came out quite black, but I haven't changed them yet. The car starts when I accelerate fully, and when it does start, it's very unstable until it idles on its own. It's very difficult to start the first time. I checked the compression, and it reads up to 70 and then starts to drop. The compression gauge might be faulty! But I put one in my car, and it reads up to 105 and then starts to drop. When I take the Monza for a test drive, it runs quite well, but sometimes when I accelerate hard, it backfires through the TBI. Then, after stopping for about 10 minutes, it won't start again until the battery dies. I hope this is clearer and that you can help me.

My friend, the compression is very low, but the very black spark plugs are due to another issue; it's due to excess fuel. Check the temperature sensor; replace it. It costs around 4000 Chilean pesos. That will improve starting and eliminate the black spark plugs. Do that first, and then look at the gasket. But you definitely have low compression.

Well, I changed the gasket and the temperature sensor looks relatively new. Now I've managed to get the car to start properly. The problem I'm having now is that after driving around for a while, it starts immediately but doesn't maintain speed; it stalls right away. Let me explain: it starts, accelerates up to 2000 RPM, the RPMs drop, then rise again and stall. When I accelerate, it stalls again. For your information, I replaced the TBI with another one that came with the IAC sensor, etc., and now this is happening. What could it be?