Intermitant stalling hard starting replaced ecm, icm, crank sensor, fuel filter, map fuel pressure 40psi at idle and running, no decrease when shut off coils check out fine, strong spark 1989 buick century 3300 engine

Sounds like fuel pressure issue, seen these symptoms many times, so I would start with fuel filter. Fuel pressure module can also be the problem, but without seeing what codes it may be throwing, hard to say. Go to Autozone or Advance Auto and they will put diagnostic reader on it for you and this may help narrow down your problem.

Good luck, FREE-PPV

Have you done basic tests, such as fuel pressure? Coolant temp sensor? Crank sensor?

clean the idler on the intake and also clean the throttle sensor, it would also be best to change the air filter and clean the maf sensor. Idler does more than just idle vehicle it controls low revs, and drop down from reves. throttle sensor tell ecu what air to add to the fuel. and the MAF tells ecu how much air is coming into the intake. also check for broken cracked vacuum lines.

Has anyone checked base fuel pressure with a gauge ?

Have checked the idle air control valve. If stuck closed it will not allow air to bypass the throttle therefore it will start and stall.

You need the exhaust converter so the O2 sensor can
work properly

It sounds as though the converter is blocked,as well
as the fuel trim, if that is correct term for an OBD1 System,
is not able to report back the oxygen in the failed converter

So the ecm can not provide the correct fuel mixture by
pulsing the injectors

I would also expect the timing chain to have a lot of slop
& possibly be off a couple teeth, from worm plastic gear
on cam

Check the ECM part number. If it is a 1228253 that is your problem. get a 16198264 the other number does just what your car is doing. I worked at a Buick dealer and know about the problematic 1228253 ecm.

Check the Idle Control System

Idle speed is controlled by the Idle Air Control Valve (IACV). The IACV changes the amount of air being bypassed to the intake manifold, in response to electric current controlled by the ECM. When the IACV is activated, the valve opens to maintain proper idle speed.

Symptom and Subsystems to Check:

1. Difficult to start engine, when cold--check Fast Idle Thermo Valve.

2. Fast idle out of spec, when cold:
a. Check Fast Idle Thermo Valve.
b. Check IACV.
c. Check idle adjusting screw (see Section C).

3. Rough idle:
a. Check hoses and connections.
b. Check IACV.

4. RPM too high, when warm:
a. Check IACV.
b. Check Fast Idle Thermo Valve.
c. Check hoses and connections, check Power Steering Pressure Switch Signal, and check idle adjusting screw.

5. RPM too low, when warm:
a. Idle speed is below specified rpm, with no load--check IACV and idle adjusting screw.
b. Idle speed doesn't increase after initial start up--check IACV.
c. Idle speed drops in gear (automatic transmission)--check automatic transaxle gear position switch signal.
d. Idle speed drops when AC is on--check air conditioning signal and IACV.
e. Idle speed drops when steering wheel is turned--check power steering pressure switch signal and IACV.
f. Idle speed fluctuates with electrical load--check hoses and connections, IACV, and Alternator FR Signal.

6. Frequent stalling, while warming up--check IACV and idle adjusting screw.

7. Frequent stalling, after warming up--check idle adjusting screw and IACV.

Additional Steps:

. Check Alternator FR Signal. Have alternator inspected, if idle speed fluctuates with electrical load. The FR signal communicates to the ECM how "hard" the alternator is working to meet the electrical demands of the car, including the battery and any loads which aren't monitored by the ELD. This square-wave signal varies in pulse width, according to the load on the alternator. The ECM places, approximately, 5 reference volts on the wire. The voltage regulator will drop this signal to approximately 1.2 volts, in proportion to alternator load. The ECM compares the electrical load (ELD) signal with the FR (Charging Rate) signal from the alternator and uses that information to set the idle speed and turn the alternator on and off. This helps fuel economy.

. Clean main ECM ground on thermostat housing.

. Reset ECM, by removing the 7.5 amp Back Up Fuse, in the under-hood fuse box, for 10 seconds.

. Replace PCV Valve, cleaning hose with brake cleaner spray.

. Substitute a known-good ECM. If symptom goes away, replace original ECM.

Check the ICM (Erratic RPM and PGM-FI System)

When the engine is cold, the air conditioner compressor is on, the transmission is in gear (automatic transmission only) or the alternator is charging, the ECM controls current to the Idle Air Control (IAC) Valve to maintain correct idle speed. Here's an overview of how the PGM-FI System works.

Background:

Various inputs to the ECM are TDC/CKP/CYP Sensor, MAP Sensor, ECT Sensor, IAT Sensor, TP Sensor, HO2S, VSS, BARO Sensor, EGR Valve Lift Sensor, Starter Signal, Alternator FR Signal, Air Conditioning Signal, Automatic Transmission Shift Position Signal, Battery Voltage (Ignition 1) Brake Switch Signal, PSP Switch Signal, ELD, and VTEC Pressure Switch.

Inputs are received and processed by the ECM's Fuel Injector Timing and Duration, Electronic Idle Control, Other Control Functions, Ignition Timing Control, and ECM Back-up Functions. These are the primary functional areas within the ECM.

Outputs from the ECM control Fuel Injectors, PGM-FI Main Relay (Fuel Pump), MIL (Check Engine Light), Idle Air Control (IAC) Valve, A/C Compressor Clutch Relay, Ignition Control Module (ICM), EVAP Purge Control Solenoid Valve, HO2S Heater, EGR Control Solenoid Valve, Alternator, Lock-up Solenoid Valve A/B (A/T), VTEC Solenoid Valve, and Interlock Control Unit.

Idle RPM:

Once you understand how the PGM-FI system is configured, it's easy to see how the ECM, Idle Air Control Valve, and the Ignition Control Module affect idle rpm. If the ECM's Electronic Idle Control function is not working properly, then it cannot properly control the IAC Valve. Likewise, if the ECM's Ignition Timing Control function is not operating properly, it cannot properly control the ICM (igniter). Obviously, idle rpm will also be affected if there's a problem with the IAC Valve or the ICM. As stated above, the ECM controls current to the Idle Air Control (IAC) Valve to maintain correct idle speed. This cannot happen if the IAC Valve is failing. The same situation exists if the ICM is failing. The ECM will tell the ICM to open and close the primary voltage circuit going to the coil and it won't respond properly. The result will be erratic spark plug firing and erratic rpm.

Conclusion:

If you are experiencing erratic idle rpm, try and isolate whether the problem is caused by the ICM (ignitor), IAC Valve, or the ECM. My experience has been that a failing ICM is usually responsible for the problem. Keep in mind that tachometers are connected directly to the ICM. Therefore, a fluctuating tachometer needle is often a dead giveaway. Heat and poor preventive maintenance (causing high secondary voltage to be discharge on internal distributor components) frequently causes the ICM (and coil) to fail. Besides performance, this is another reason why it's important to regularly replace spark plugs, spark plug wires, rotors, and distributor caps. Electricity will always follow the path of least resistance, even if it isn't the intended one. Our job is to ensure the intended path is the path of least resistance.

Ignitor (ICM) and Coil Replacement:

1. Disconnect negative battery cable.
2. Remove hex head machine screws, securing distributor cap to housing, using an 8 mm nut driver.
3. Move distributor cap and wires off to the side.
4. Remove machine screw securing rotor to shaft, using a #2 Phillips head screwdriver. It may be necessary to "hit" the starter once or twice, in order to rotate rotor for access to mounting screw.
5. Remove rotor and leak cover.
6. Unfasten ignitor wires, remove coil mounting screws, and set coil aside. Note: Removing coil first improves access to igniter.
7. Unfasten screws securing igniter to housing.
8. Remove ignitor from distributor and unfasten screws mounting ignitor to heat sink.
9. Coat back of new ignitor (or old igniter, if reusing) and male connectors with silicone grease. Silicone grease increases heat transfer to heat sink. Failure to apply silicone grease will cause the ignitor to quickly fail.
10. Mount ignitor to heat sink and reinstall ignitor, igniter terminal wires, coil, coil wires, leak cover, rotor, and distributor cap. Ensure female ignitor terminals fit snugly--crimp with pliers, if necessary.

AutoZone can test ICMs and coils for free. If you plan to keep the car, I would replace the ICM due the age of your Civic.

I would install a new fuel filter. You might want to replace the spark plugs and wires at the same time. I would install a new fuel filter and see how it runs.

Crank sensor!