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AMEDEE
AMEDEE, CHEVY TECHNICIAN
Category: Chevy
Satisfied Customers: 25432
Experience:  ASE certified tech ADVANCED LEVEL SPECIALIST. Wisconsin certified emissions state inspector
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I have a 1993 Chevy K1500 with a 350 engine.

Customer Question

I have a 1993 Chevy K1500 with a 350 engine. When it is cold it runs fine in neutral or park, I can rev it up and it sounds good although if I leave it idle it will sometimes die. As soon as I put it in gear and try to drive it, it runs really rough and almost dies. This continues as I go down the road and gets worse as the engine gets warmer. What I found out is that if I put it in neutral turn off the ignition and coast and restart the engine it will run better for a minute or so before it starts sputtering and running rough again. I have changed the fuel filter, oxygen sensor, throttle position sensor, egr solenoid and ignition module. There don't seem to be any vacuum leaks.
Submitted: 6 years ago.
Category: Chevy
Expert:  AMEDEE replied 6 years ago.
Hello!

Have you checked the computer for codes?

Does the engine actually misfire or just idle rough?
Customer: replied 6 years ago.

The check engine light does not come on so I haven't checked for codes. The engine will misfire but only after it has been running rough for a while and is fully warm. It acts like it is getting too much or not enough fuel. When I look into the throttle body it seems to be getting plenty so I'm guessing it is getting too much.

 

Expert:  AMEDEE replied 6 years ago.
Does it do this at idle or under a load?

Did you say the tune up parts were replaced or not?
Customer: replied 6 years ago.
Under a load. The spark plugs are fairly new, I replaced them a few months ago. The cap rotor and wires are not new but are not super old.
Expert:  AMEDEE replied 6 years ago.
From what you are telling me, it sounds like you might just need a tune up. No, not just plugs, but a full tune up! The whole nine yards! Any part of the secondary ignition will do this including the ignition coil or coils! This sounds like a classic ignition misfire! They usually go bad under a load like under acceleration, but can be noticeable at any time. It is very important to have your engine equipped with good tune up parts or you may be causing damage to other components of you car like the catalytic converter which can be expensive!

Possible causes:

Ignition misfire causes by any bad tune up part and or ignition coil or coils.
Bad spark plugs, spark plug wires and cap and rotor (if equipped)
Wrong tune up parts spark plug, wires etc...

Insulator cracks.
Wear.
Improper gap.
Burned electrodes.
Heavy deposits.

The quickest way to check the ignition components, is by looking closely for leaking secondary voltage. Visual look at all the tune up parts to see if you can see any sparks coming from any of the wires or coil (or coils) when the vehicle is running. If not, you can put your hand on the coil/coils and wires when the engine is running and see if you feel any small voltage leaking form the tune up parts. Check spark plug wires by connecting ohmmeter to ends of each wire in question. If meter reads over 30,000 ohms, replace wire(s).
ALso, with engine running, spray coils and plug wires with fine water mist to check for shorts.

It will leak secondary ignition voltage from the tune up parts caused by high resistance from carbon tracking if they are bad. This is very common if the tune up parts are not changed regularly!

If any is found, the tune up parts are simple bad an will need to be replaced! If none is found than you can spray a mist of water on the tune up parts when the engine is running and see if that causes the engine to stumble or run rough at all. Again, if it does, the tune up parts are bad and will need to be replaced!
Customer: replied 6 years ago.
I will check those things again, but the thing that puzzles me is that if I turn off and then restart the engine as I am going down the road it makes it run better for a while. What explains that?
Expert:  AMEDEE replied 6 years ago.
It could be a bad pickup inside the distributor...

Also, be sure the fuel pressure is up to par.
AMEDEE and 5 other Chevy Specialists are ready to help you
Customer: replied 6 years ago.

Since it went from running great to running bad all at once, it seems unlikely that it is worn tune up parts, but I will check to see when they were replaced and will check them out. Since it gets better when I restart the engine, even when it is warm, it seems unlikely that it is the pick up in the distributer. If you have any more ideas, let me know, otherwise I'll get back to you after I check these things out.

 

Expert:  AMEDEE replied 6 years ago.
If you disconnect the egr valve, does this problem get any better?
Customer: replied 6 years ago.
It turned out to be the fuel pump. Your answers were pretty random and not very well thought through before you would jump to a conclusion. It would have cost me quite a bit of money to follow your advice for parts that were unnecessary. I appreciate your willingness to help, but you should think through your answers before to give them.
Expert:  AMEDEE replied 6 years ago.
Hello!

Thanks for the accept!

My recommendation is to check every component to be sure it is bad before replacing it. I do apologies.. maybe I was not clear.

I am just bring up some possibilities to help you.