1990 Chevy Lumina Accelerates Slowly Dies in reverse

[TragicRealm]

I have a 1990 chevy lumina 2.5 L 4 cyl. 100,000 miles....The car recently started chugging while in drive and will not accelerate correctly, when I do get it to 55 mph theres still chugging, Ive replaced the fuel filter, spark plug and wires, fuel system clean, new battery, there is a inch crack in the exaust manifold on the front of the engine, not sure if that would make me lose power to accelerate, the car idles fine, but chugs when put in drive, and will occasionally die when put in reverse....PLEASE HELP

[Schurkey]

The crack in the exhaust isn't helping. May be screwing with the O2 sensor by letting air into the manifold.

Other parts of your symptoms sound like a plugged catalytic converter.

You need a scan tool for real diagnosis, and also a restriction test of the exhaust. What is the fuel pressure?

[jeffcoslacker]

I'm trying to remember that far back...seems like the older ones had the MAP sensor on the firewall rather than mounted on the engine? Or got the MAP vacuum from a common source block on the firewall?

I remember ones set up like that, the vacuum hose would go bad, and suck air when the motor pitched fore and aft while running. So like for instance the engine starts to pull, rolls back on the mounts, this opens the crack in the vac hose, that makes the MAP sensor reading go bonko, the engine sags, the crack closes up, the engine starts to pull again, the crack opens, etc...causes a feedback loop as long as the motor is rocking around.

And since the motor torques and rolls the other direction in reverse, it may put the bad vac hose under even more of a bind and cause the stall.

Just a thought. Easy to check and fix. Those hoses can also collapse and suck shut in the weak area, so replace the whole thing no matter whether you see a crack or not, if it runs from the motor to the firewall like I'm thinking.

[jeffcoslacker]

Autozone says your MAP is here:

Under hood, passenger side, upper engine area, mounted on air filter housing

Locate it, follow the vacuum line, see where it goes and what kinda shape its in. MAP looks like this