1978 Cadillac DeVille - Issues when starting

my 1978 caddie had a drag starting problem, Replaced the alternator, battery, starter, and a negitive battery cable. Now it has no power, took it back, now when cold missfires spits, stalls. and not as much power but when warm it seem to be fine but now get up and go

When is the last time it had a good time up?
Spark plugs spark plug wires distributor cap rotor?
I take it that is a carbureted vehicle possibly an issue with a choke or choke pull offs, if it is a general motors four barell quadrajet, possible stuck power piston.
Make sure the timing is correct and make sure the vacuum advance is working and the centrifical distributor weights in the distributor are free.

it would also help to know which engine you had and what has been done to it.

Year
1978
Engine No. Cyl. Disp. CI (L)
8-350 (5.7)
Fuel Delivery
EFI
Engine Manufacturer
Oldsmobile
Spark Plugs - Origional Type, Gap (in.)
R47SX 0.060
Distributor Point Dwell (Deg.), Point Gap (in.)
Electronic (HEI)
Ignition Timing Deg. BTDC (Auto. Trans)
10B (8B)
Intake Valve Opens BTDC
22°
Fuel Pump Pressure
5.25-6.5 PSI
Idle Speed (Auto Trans)
650 RPM


Year
1978
Engine No. Cyl. Disp. CI (L)
8-425 (7.0)
Fuel Delivery
4V Carb.
Engine Manufacturer
Cadillac
Spark Plugs - Origional Type, Gap (in.)
R45NSX 0.060
Distributor Point Dwell (Deg.), Point Gap (in.)
Electronic (HEI)
Ignition Timing Deg. BTDC (Auto. Trans)
18B @ 1400 RPM
Intake Valve Opens BTDC
21°
Fuel Pump Pressure
5.25-6.5 PSI
Idle Speed (Auto Trans)
650 RPM


Year
1978
Engine No. Cyl. Disp. CI (L)
8-425 (7.0)
Fuel Delivery
EFI
Engine Manufacturer
Cadillac
Spark Plugs - Origional Type, Gap (in.)
R45NSX 0.060
Distributor Point Dwell (Deg.), Point Gap (in.)
Electronic (HEI)
Ignition Timing Deg. BTDC (Auto. Trans)
18 @ 1400 RPM
Intake Valve Opens BTDC
21°
Fuel Pump Pressure
39 PSI MIN.
Idle Speed (Auto Trans)
675 RPM

You have a choke/carburetor problem, you need to find a specialist that works on carburetors.

99.9% chance your Cadillac has the 425 4-barrel engine.

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Not related to starting, but to power loss. Does your 78 have catalytic converters? May be clogged.

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Yes, it SHOULD have one catalytic convertor… the old bead style…assuming someone did not remove it decades ago!

+1
The problem for the OP will be finding a shop that has an “older” mechanic because the younger mechanics might not have ever worked on a pre-fuel injected engine, and even if they did, they might not have the expertise of an older mechanic.

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And a ‘78 with a carb is the worst of the worst, with all the poorly designed pollution controls.

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Too bad the OP is not around me.
I worked in tune-up shops in the early and mid 80s.
Did a lot of those carburetors and choke pull offs adding tension to the choke springs if needed, installing and adjusting choke pull offs for drivability issues, replace vacuum advances oh I just thought of something too that particular ignition system sometimes the wires to the pickup coil would break internally and only be held together by the insulation of The wire unplug the vacuum advance hose, (assuming the vacuum advance is working) and plug it off and the hesitation and missing would go away pulling the distributor and replacing the pickup coil would solve the problem.

A ‘78 anything, not just a Cadillac.

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Perhaps when the alternator was changed a vacuum hose to the carburetor came off. The problem is going to be finding a shop with a mechanic who has enough gray hair to work on your car.

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Intake manifold leak? Carb gasket?

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