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

[Joeyatwell5]

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

 

[movietvet]

Welcome to the forum from Oregon.

Sounds like you addressed the ignition parts and as long as you used good quality components, you should be fine there.

Sounds like the loss of power could be fuel pressure related. It also sounds like you have no idea of components or filters age. I would replace the fuel filter. Could be restricted and robbing pressure from the fuel system. A clogged fuel filter can also make a fuel pump work too hard and cause failure prematurely. Do the fuel filter and get a fuel pressure test done and reports results here. Get the pressure at start up and idle, as it warms up and while driving under a load.

 

[registered-bum]

" but it gradually gets worse"
... as in sputters and stumbles?
... as in idle speed slows until it stalls?

 

[movietvet]

" but it gradually gets worse"
... as in sputters and stumbles?
... as in idle speed slows until it stalls?

As in losing fuel pressure...
I see what you are saying though. Just sitting there idling or while driving?

 

[Joeyatwell5]

As in losing fuel pressure...
I see what you are saying though. Just sitting there idling or while driving?

Just sitting there idling, I’ll throw the parking brake on and put it in gear and it does the same thing

 

[Joeyatwell5]

" but it gradually gets worse"
... as in sputters and stumbles?
... as in idle speed slows until it stalls?

Yes, it will start to sputter and then stall

 

[movietvet]

Only in gear or will it do it idling in neutral or park?

 

[movietvet]

Pull the IAC valve and clean port and pintle.

 

[PAIRA90S]

Vacuum leaks? I've experienced a higher idle(cold eng.) overcomes them and they become create issues as it warms up.

 

[Joeyatwell5]

Pull the IAC valve and clean port and pintle.

I bought a new IAC and that didn’t seem to fix the problem