Idle gets gradually worse after replacing distributor cap, rotor, plugs, and plug wires

[udidwht]

Vacuum leak/s. Confirm you have none otherwise, you'll be chasing your tail around.

 

[udidwht]

I’m not really sure where I would be looking for the vacuum leaks

The base gasket for the TBI is a common culprit. Also, check the throttle ends. Have you confirmed you fuel pressure?

 

[Scooterwrench]

OK,you were down on power but the truck was running until you change plugs, wires, cap and rotor. Now the truck won't run. Check to make sure you put the plug wires on in the correct order. If you bought the cheapest bargain basement parts you could buy then you probably got what you paid for.

 

[Erik the Awful]

Now it will start and sound like it’s running good but it gradually gets worse

Most likely a vacuum leak. Your fuel mixture is enrichened when the engine is cold, covering up the vacuum leak, but as it warms up the ECM turns the fuel mixture leaner, and it starts running like crap.

Change the distributor. Cheap fix. Distributors are notorious for internal corrosion due to lack of ventilation. Check for excessive rotor movement.

Not good advice. Yes, the distributors are old and can have issues, but the original distributors - if aluminum and not plastic - are better that what's avaialble now. Also, diagnose the problem before throwing parts at it.

 

[Sabinoerc]

2nd post was suggestion to check your fuel pressure. I didn’t see that it’s been checked?
marginal fuel pressure can cause all sorts of problems, including idle problems.
My view - I wouldn’t do anything else until getting a fuel pressure reading - between the fuel filter and the TBI.

 

[Selrahc360]

I’ve got a 91’ k2500 with a 5.7, 350 tbi and was experiencing loss of power while driving home from work, asked a buddy who’s a mechanic and he said it sounded like the distributor cap so I pulled that off and it was all corroded as was the rotor. After replacing those I tried to start it, it started and was running rough, so I decided to pull the plugs and they were covered with soot and replaced those and for the hell of it I replaced the wires. Now it will start and sound like it’s running good but it gradually gets worse, I’m stumped here and just looking for more input on what I should check to solve this issue

Check the gear on the end of the distributor for wear