1980 Cadillac Biarritz 368 running rich and lost of vacuum

ever see the truck run perfect before, or not in 10 years?
C2500 right not k2500 ,pickup.
NO ENGINE told ,4 engines 3 gas 1diesel.
but is gas so 4 engine not told (no fun there, blind)
4.7 to 5.7L and 5.4L gas.
crankshaft and cam forgot to say sensor?
CAB means distrib CAP .
rotor sure.
why not new SPARK PLUGS first and for sure those ratty old HV spark wire, useless, I run NGK mag wires.

battery good, cranks fast and engine spins fast and does not start.
and engine compression is good
and we test that spark is good on all 8 cylinders not just one,all 8 are test
and also tested for spark timing. for sure if distributor was removed, or set loose at base and timing lost.

if all that is good the engine now runs on spray test fuel in a can. for 3 seconds, even with fuel pump fuse pulled.
if you get this far,
we check fuel pressure next and even for bad fuel.
no history of car told
bad fuel ,old rusty tanks wreck injectors.
26 year old truck,.

things bad that old are, all fluids and belts
fuel filter packed in gunk and rust.
thermostat bad.
spark parts bad, cap/rotor wire sets x8 and spark plugs. (or timed wrong or put back wrong firing order)
injectors clogged, bad fuel or rust in the tank
bad FPR, bad map sensor.(or only clogged)
or bad fuel pump if pressure is low and FPR not bad.

most of my tests all take tools and meters
a tech can not fix cars lacking his tools.
and skills to use them./
even a timing light is needed on all distrb cars
and all EFI cars a fuel pressure gauge.
and compression gauge
and vacuum gauge.

It could be a few different thing's , testing to find out the problem , rather then just replacing parts is the proper way to fix vehicles . Checking engine sensor data with the proper factory or equivalent scan tool . Could be a vacuum , leaking fuel pressure regulator, map sensor . CPI injection system under the intake manifold . Chev GMC Misfire poppet injector diagnosis troubleshooting and replacement

Have you checked fuel pressure and did you figure out why you lost electric power ?

How about timing chain being worn & gears stripped ?

Put a timing light on it, then put the pick up on a wire
half way thru the firing order & see if they timing is
the same.

Pull the vacuum hose off of the fuel pressure regulator and the map sensor and if you see any fuel run out of either of them then replace the regulator.

Hello! when you say you checked the MAP sensor what do you mean? Did you take voltage readings at idle ? A vacuum leak is the likely culprit, especially to the MAP...The minor shake at idle being the major clue...Send a comment...guru..saailer

I’m happy to help further over the phone at https://www.6ya.com/expert/david_6df67de3b14de867

Clean the throttle body. Check the mass air flow sensor for corrosion of the wire harness connector.

There are three components that will enrich the fuel mix: 1)engine coolant temperature sensor. If this is not working or the signal is interrupted by a wire breakage then the engine will run rich. The coolant sensor informs the ECU (high resistance) that the engine is cold at start up and so the ECU responds by increasing the fuel injection cycle to enrich the fuel air mix. Later on as the engine warms the resistance of the coolant sensor drops and the injection cycle is reduced by the ECU. If the sensor is faulty or has become disconnected (wire break or corrosion of the socket pins) the ECU assumes that the engine remains 'cold' and the engine runs permanently rich. 2) O2 sensor, operates completely independently of the EGR, if it is faulty and signals 'too much oxygen' then the ECU will significantly enrich the fuel mix to try and balance what it thinks is an excess of air. 3) Fuel pressure regulator. If the diaphragm has broken or there is a leak in the vacuum line this will result in higher than needed fuel pressure in the fuel rail at idle. The vacuum line acts against the spring pressure holding the valve closed. At idle, the inlet vacuum pulls back on the diaphragm reducing the fuel pressure required to open the valve. Low fuel pressure coupled with short duration injection times will mean a lean mix at idle. If the vacuum is compromised or the diaphragm damaged then the increase in rail pressure will make the fuel mix very rich to point of flooding the engine

A faulty map sensor will make it run rich and so will a bad or misadjusted TPS but it should try to crank. Check mat sensor. A stopped up converter will do this to.

Hello,
your problem appears to be the idle control motor located on the air intake manifold it is a small motor that goes bad quite often. Other items that can cause this is a bad /clogged air filter or a tune up (spark plugs and wires), or clogged fuel injectors. to clean the injectors you can buy a container of fuel system cleaner and pour it into the gas tank and as you drive it cleans the system.

Once the fuel system is cleaned via a tankful of cleaner & gas then the idle controller motor would be next on the list to be replaced.

Good Luck !
Rich Lilja