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Truck Won't Run Right.

wagonproject

By wagonproject
in Ask A GM Technician

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wagonproject Enthusiast

wagonproject

Posted
Posted

My 1996 silverado (305) was in storage for 10 years. I got it out this spring and replaced the gastank, fuel pump, fuel filter, spider injector, plugs, wires, cap, and rotor. It ran great for 2-3 months and just the other day I was driving it and felt like it was hesitating. When I start it now it runs rough and when you give it gas it runs rough. You can go a few feet and sometimes it will shut off. I took a friends cheapo scanner and ran it and got these codes.

 

P0102

MAF or VAF

Circuit low input

 

02 sensor heater

Circuit malfunction

(Bank 1 sensor 3)

 

P0300

Random multiple

Cylinder misfire detected

 

P0420

Catalyst efficiency

Below threshold

Bank 1

 

Now after I read those codes I cleared it and ran it again and got only the P0300 again. So it must have to run for a while before it throws the other codes?

 

I took it to a local shop he said it needed a tune up and even then he wasn't sure if it would run without more things. So I just brought it home. He did say it needed a new cap as the one I just put on was sparking on the outside. He told me to go buy a NAPA cap. So I am going to go buy one tomorrow.

 

Any ideas on what else to check?

tylerjenkins92@aol.com Senior Enthusiast

[email protected]

Posted
Posted
My 1996 silverado (305) was in storage for 10 years. I got it out this spring and replaced the gastank, fuel pump, fuel filter, spider injector, plugs, wires, cap, and rotor. It ran great for 2-3 months and just the other day I was driving it and felt like it was hesitating. When I start it now it runs rough and when you give it gas it runs rough. You can go a few feet and sometimes it will shut off. I took a friends cheapo scanner and ran it and got these codes.

 

P0102

MAF or VAF

Circuit low input

 

02 sensor heater

Circuit malfunction

(Bank 1 sensor 3)

 

P0300

Random multiple

Cylinder misfire detected

 

P0420

Catalyst efficiency

Below threshold

Bank 1

 

Now after I read those codes I cleared it and ran it again and got only the P0300 again. So it must have to run for a while before it throws the other codes?

 

I took it to a local shop he said it needed a tune up and even then he wasn't sure if it would run without more things. So I just brought it home. He did say it needed a new cap as the one I just put on was sparking on the outside. He told me to go buy a NAPA cap. So I am going to go buy one tomorrow.

 

Any ideas on what else to check?

 

If it's been sitting for 10 years, then you probably need to clean the throttle body and check wires for mouse chew marks.

rodram Enthusiast

rodram

Posted
Posted

I agree that you should get a new dist cap (if someone has reported arcing around the cap)... you could get a NAPA, or an ACDelco would be the best..

 

AND also....

 

- does it start cold ok, and then run like crap after it warms up...?

 

... if so.. I would check the CTS (coolant temperature sensor) on top front of the engine beside the thermostat

 

.. this sends a control signal to the Powertrain Control Module (PCM) to regulate the fuel mix depending on the engine temp... when they fail, they just keep pumping the rich fuel mixture to the injectors (as if the engine was still cold)

 

.. cheap part, easy to check, easy to replace if necessary, ... much grief if not working properly

wagonproject Enthusiast

wagonproject

Posted
  • Author
Posted

Put a new cap/rotor on. Runs better but still not 100%. And no, it acts up right away. But ill check that part.

 

Thinking it may have to do with the cat or some sensor according to the codes.

  • 2 weeks later...
wagonproject Enthusiast

wagonproject

Posted
  • Author
Posted

Still trying to get this truck going. Got to move it out of the shop now.

 

The MAF sensor is broke also. The piece that the wire plugs in to on the MAF sensor is broke so the connector is held in with a ziptie. Seems to screw up the motor as its not getting a constant feed all the time. Any recommendations on where to pick up a good one at?

 

If I put a new 02 sensor on (the 3 one, the one after the cat) will it do any good if the cat is still bad?

rodram Enthusiast

rodram

Posted
Posted

... here's another thought ... I know you said you replaced the fuel pump.... BUT..

 

get a fuel pressure tester and check the fuel pressure .. low fuel pressure can cause the randomn misfire P0300, poor starting, and the poor driveability...

 

and .. fuel pumps can fail quickly ... some brands are just not that reliable... (ACDelco or Delphi are the most reliable... ie., less chance of having to replace the pump again soon)

 

if the fuel pressure is up (spec is 61 to 66 psi and the truck would not be expected to start or run properly if below 58 psi), then I would look to the ignition module .. get it tested (sometimes a bad one will still pass until it is tested 3 or 4 times ... fail as it warms up)

 

... and sorry, I don't know anything about MAF sensors

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