running problems

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TravisS
Posts: 2
Joined: Sun Apr 20, 2014 6:09 pm

running problems

Unread post by TravisS » Sun Apr 20, 2014 6:21 pm

i have a 1993 chevy 1/2 ton truck 5.7 L V8, when i start it it dies i replaced plugs,wires,distributer, coil, fuel filter. when i unplug the map sensor and the sensor that is right at the front of the motor where the water comes in it will idle but it will not drive when i put it in gear, it just dies. anybody with any info please help!!!

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carriedi
Posts: 2573
Joined: Wed Apr 10, 2013 12:42 pm

Re: running problems

Unread post by carriedi » Mon Apr 21, 2014 12:18 am

well, I would say scan the engine to see what it shows is happening as far as the computer is concerned. You might want to forget the codes you may have entered into the system by unplugging things.

have you tried to start it with your foot opening the throttle a little so that when it starts you are controlling the air so it's more than just idle? or, once it starts you keep the throttle moving to see if you can keep the engine running?

Have you measured what your fuel pressure is? (9 - 13psi) you might want to see if when the car dies does it still have good fuel pressure, are the plugs still getting spark and are the injectors still firing. by finding out which of these things goes away , it will lead you to look in the right direction. Ignition module, (or distributor), ecm, fuel pump, poor connection to power or ground...
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TravisS
Posts: 2
Joined: Sun Apr 20, 2014 6:09 pm

Re: running problems

Unread post by TravisS » Mon Apr 21, 2014 7:54 pm

when i get it started i throttle, it thats the only way to keep it goin. when i unplug those sensor it will idle as smooth as a brand new truck for awhile then it dies.

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carriedi
Posts: 2573
Joined: Wed Apr 10, 2013 12:42 pm

Re: running problems

Unread post by carriedi » Mon Apr 21, 2014 10:14 pm

when you unplug the coolant temp sensor and the map the engine will run richer. the coolant sensor unplugged will have a default unplugged sensor reading of -40F. That will make the injectors stay open longer just as if your choke was on in a carb car. But that is before your computer really kicks in and looks at everything to set your fuel mixtures. You should stop unplugging stuff because it will make the computer screw up other things. by unplugging sensors the computer will see those things as being bad. Then it has codes that you won't know if they are actual codes or codes because you put them in there.

You can do maintenance and mechanical things to see if they make your truck run better. But it would be very rare that you can cut off sensors from the computer and have the computer do a better job. You should have your computer scanned to see what the actual reading are. If the engine seems to run better with pieces turned off maybe you should look to see if your fuel system is running rich enough. is your fuel pressure to low? Look at your injectors as the engine is running. do they both have a good spray pattern? While you are watching the injectors and the truck dies, do the injectors have a good strong spray pattern all the time before it dies or does the spray seem to piddle out and then it dies? If you have a can of carb cleaner, when the truck seems like it's about to die can you keep it running with carb spray? (Be careful though, a backfire could cause a fire ball to come out of your throttle body) If the fuel system stops but you cab keep it running with carb spray as fuel then you need to look at fuel pressure and/or fuel injector pulse. (DO NOT USE STARTING FLUID! USING STARTING FLUID TO KEEP AN ENGINE RUNNING COULD DAMAGE YOUR ENGINE)

A scan tool and a fuel pressure gauge are tools just like a spark plug socket and ratchet. If you want to work on today's vehicles you are going to need to use tools that can help you know what your car is doing. A scanner will also tell what your Idle Air Control solenoid is doing. If you can keep the engine running by opening the throttle more than normal idle, that might tie in to your problem.
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