My 1992 dodge grand caravan with the 3.3, will crank and run for about 45 minutes then it dies and won't start back up for about 25 minutes. I have replaced the computer, ignition coil and the idle air control motor and it still does the same thing. The on bord diagnostic code says the ecm lost power in the last 100 cycles and back up power was lost. I havewent through most of the wiring harness also and still no fix. Someone please help.

Hello, Joshua, Replace your vehicle fuel filter for one thing. Next, is your vehicle getting hot and what I mean by this is. Does the vehicle temperature exceeding it normal operating temperate? If it get hotter than normal.

Then you'll need to have the radiator cleaned and the engine cooling system flushed.

What cause it to stop running in 25 minutes of run time. The problem is fuel and it properties. Such as, additives and especially alcohol of 10% or better add to the fuel. This will cause the fuel to evaporate-----Vapor Lock----engine can burn and process vaporized fuel. Couple of things here, OK. Faulty fuel filter, weak fuel pump, faulty fuel regulator if your vehicle is fuel injected. If fuel injected then the fuel will vaporize in the fuel rail the set upon the fuel injectors. If the engine is carbureted then fuel is vaporizing in the fuel line and in the fuel bowl in the carburetor. This will apply to throttle body carburetor also.

Recommend. Do not use fuel that has alcohol added. Change fuel filter, check fuel press, if the pressure is to low change fuel pump. If the engine is running hotter than normal. Have compressor test on the cylinders (this test will verify leaky head gasket, faulty valves, piston ring are bad). Have the radiator cleaned out, Flush the engine to clean cooling gallies in the block. Have new anti-freeze installed with 50/50 mixture (50% anti-freeze and 50% water). GB....stewbison

I suggest replacing (if not already) the EGR valve. Check all vaccum lines and make sure they are in good repair.
Also, consider replacing the MAS (mass airflow sensor); however, first clean it with MAS cleaner, (local auto parts dealer). Remove MAS (located between airfilter housing and intake {throttle body} ). Spray cleaner from both directions (if applicable) generously - let sit for about fifteen minutes to airdry then reinstall - start vehicle and drive. If the problem persists, be sure that you have checked all the above from what Richard Brooks has mentioned and suggested, as he is right. Loose wires, bad grounds, or even the positive cable can cause such issues, which in turn cause multiple malfunctions of other units.
Please let me know if you need further assistance.
carsandcomps

I have seen similar problems but not exact...First of all / Have you ever changed your radio ? Do you know that it is not getting hot and shutting itself off ?...I have seen the temp.gauge be faulty and make the vehicle think it is hot and shut itself off...and be sure you have a good alternator and battery...also make sure the cables are good and tight...I have seen a loose ground cable cause the same thing also..The negative cable being loose will cause an ECM code that is false...Be sure they are both clean and tight...Hopefully you disconnected the battery when you changed the computer...If not ...Disconnect the neg.cable and allow it to reset itself...It may to to be just reset..Hope this helps..Metalpoet