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Tim's Auto Repair
Tim's Auto Repair, mechanic
Category: Chevy
Satisfied Customers: 13231
Experience:  Have owned a repair shop for 25 yrs.
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I have a 1990 chevy 4x4 silverado 2500 with a 350 engine and

Resolved Question:

I have a 1990 chevy 4x4 silverado 2500 with a 350 engine and 212k miles. It recently developed a problem. It starts easily, but misses bad and when you put it under a load, such as acceleration or going up a hill it sounds like it is knocking. It doesn't knock when idling or if you don't accelerate too much at once.

What might cause this? Also, for sometime now I must add about 1 quart of water/coolant about every 4to 500 miles. The truck doesn't run hot and there is no indication of a leak or water in the oil. Also the oil pressure is good.

Any ideas as to what is wrong that is causing the missing and knocking and where the coolant is going and could the two be connected. What can you recommend. This was my Dad's truck and I have kept it well maintained, I would like to keep it going if at all possible and I can't afford a replacement truck. Your thoughts and suggestions will be greatly appreciated! Thanks!!

Jim
Submitted: 4 years ago.
Category: Chevy
Expert:  Tim's Auto Repair replied 4 years ago.

hi

first,,tune it up if it hasn't been done lately..new plugs,wires,rotor and distributer cap.....make sure the radiator cap is good..also check around the water pump for water evaporation.it is a possibility that the head gasket to be blown,letting the coolant into the cylinder,but it isn't likely on this engine......you need to check the fuel pressure.the fuel pump may be weak...these must have no less then 9psi at all times.....i have seen on this model that the rubber fuel line from the fuel pump to the fuel sender inside the fuel tank,bust,causing the pump to suck air

thanks

 

fuel pressure
Testing and Inspection

PROCEDURE

A fuel system pressure test is part of several of the Diagnostic Charts and Symptom Checks. To perform this test, follow this procedure:

  1. Turn engine OFF to relieve system pressure.
    • Disconnect negative battery terminal to avoid possible fuel discharge if an accidental attempt is made to start the engine.
    • Loosen fuel filler cap to relieve tank vapor pressure.
    • The constant bleed feature relieves fuel pump system pressure when the engine is turned "OFF".
  1. Uncouple fuel supply flexible hose in engine compartment. Install fuel pressure gauge between steel line and flexible hose.
  2. Tighten gauge in line to insure no leaks occur during testing.
  3. Connect negative battery terminal and START engine and observe fuel pressure reading. It should be 62-90 kPa (9-13 psi). If not, refer to DIAGNOSTIC CHARTS/FUEL SYSTEM PRESSURE TEST (CHART A-6).
  4. Turn engine OFF to relieve system pressure.
    • Disconnect negative battery terminal to avoid possible fuel discharge if an accidental attempt is made to start the engine.
    • Loosen fuel filler cap to relieve tank vapor pressure.
  1. Remove fuel pressure gauge.
  2. Install new O-ring on fuel feed line. Reinstall fuel line.
  3. Connect negative battery terminal and START engine and check for fuel leaks.
  4. Install air cleaner assembly.
Customer: replied 4 years ago.

Hi,

 

Thank you for your answer. I will for sure get you paid you deserve it. I wanted to tell you something that I intended to include in my first question. I have a friend that is a mechanic that drove and listened to the truck. He suggested that he believes the miss and knock is being caused by a busted wrist pin. I don't drive this truck too many miles and about a year ago, approx. 8,000 miles ago, I had the truck completely tuned up including plugs, wires, distributor, distributor cap, radiator cap, fuel-oil-air filters, hoses and belts as well as brakes, rotors and front end components.

 

This mechanic friend told me that I shouldn't spend any more money on this motor. He recommended that I have another engine installed. Mind you he isn't doing the work so he has nothing to gain by this advice. He also told me to check on the warranty of the new engine to ensure what the requirements are regarding who installs the engine.

 

Does this information make a difference to you regarding your thoughts on my engine problem? And if so, what recommendations do you have? Again thanks for your help.

 

Expert:  Tim's Auto Repair replied 4 years ago.

well

yes it does...apparently he is hearing a mechanical knock...if this is the case,,it may be a connecting rod,it is unlikely for it to be a wrist pin,but it may be where it is connected to the crank....and he may be right ,,,,though the engine should run fairly smooth,sense your friend can hear it,you may want to take his advise on this one

thanks

Tim's Auto Repair, mechanic
Category: Chevy
Satisfied Customers: 13231
Experience: Have owned a repair shop for 25 yrs.
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Tim's Auto Repair
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Have owned a repair shop for 25 yrs.