Mechanics

STARTING PROBLEMS WHEN ENGINE IS WARM

1995 Mazda 323

Engine Performance problem
1995 Mazda 323 4 cyl Front Wheel Drive Manual 190000 miles

After many, many expensive fault diagnosis attempts at various mechanics and auto-electricians the perennial problem of not starting after engine has been run for a short period is still present. The car has had the following done to it to get to this point: -New Fuel Pump, New Radiator and Thermostat and cooling system checked, Air Flow Sensor Replaced (2nd Hand), Immobiliser Disarmed, New Battery, 2-2nd Hand Distributors, New Distributor with new leads, Major Service, Computer has been scanned for Fault Codes twice. After new distributor and leads replaced (Most recent Repair) car runs rough when cold too and has stalled and won't start just like it wouldn't when warm previously too. The failing to start problem is more frequent now than ever before. A most frustrating fault if you have to pick up groceries, fill the car up, pick kids up from daycare etc. Can you please provide some helpful direction.
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QbnPat
October 18, 2009.



There are tre things that need to be in place.
Spark- noid- fuel-
make sure the spark is very nice and blue not yellow.
Update me
spark plugg and cables checked
if there are all good my second though will go the the cranck sensor. Check for kinked fuel line, you have new fuel pump, that is good.
If everything above is good, then we will move to next that will be the igniter and the idle switch

first, update me

Tiny
Mathiaso
Oct 19, 2009.
Distributor, spark plugs and new leads very recently installed(3-4 Weeks ago just prior to first post). Spark was assessed then and this ongoing fault returned within a day of repair.

Tiny
QbnPat
Nov 1, 2009.
It is sure that the problem is Temperature Related.
And there is no code(s).
When an intermittent starting or driveability problem only occurs when the engine is hot, only when the engine reaches normal operating temperature, or only when the ambient temperature is high, the temperature is affecting something. The question is what?
Changes in operating temperature could affect the way the PCM controls spark timing, the fuel mixture and other emissions functions. If an intermittent problem only occurs after the vehicle has been driven several miles, it may be occurring when the PCM goes into closed loop. The underlying cause might be a bad oxygen sensor signal, airflow sensor signal or MAP sensor signal that is upsetting the air/fuel mixture.
If a problem seems to occur only when the engine is running in closed loop, that would tell you it’s probably a sensor or PCM-related issue. The strategy here would be to look at some of the key sensor inputs with your scan tool to see if readings are within normal limits. Some problems may occur too quickly for the normal data stream to detect a fault, so you may have to hook up a digital storage oscilloscope to detect a momentary glitch.

Temperature also can cause mechanical things to stick as a result of thermal expansion when a part gets hot. Valves and lifters can stick if an engine overheats. EGR valves can stick from heat or a buildup of accumulated carbon deposits. Relay contacts may be affected by changes in temperature, too
if the problem is not temperature related, then it could be motion related.
Motion-related intermittent problems also can occur when harmonic vibrations in the exhaust system, driveline or suspension feedback through the powertrain or chassis. This may affect the operation of certain parts or make you think your engine is running rough.
Moisture is especially damaging to PCMs and electronic circuit boards. Moisture can cause corrosion that shorts out circuits and causes all kinds of weird electronic problems. That’s why flood-damaged vehicles are so unreliable. Sooner or later, they usually need to have the PCM and/or other electronic modules replaced. Check your vehicle history.

Tiny
Mathiaso
Nov 1, 2009.