97 Vortec 454 is due for a Tune-Up - Anyone have surging at idle? slight power loss?

[JScott23]

To all Vortec 454 owners! Now my 97 is a Vortec 454/4L80E, just hit 203k.

It's all original, only thing i've replaced is spark plugs, filters and the water pump. Now lately i've noticed it's been running a little rough, a little less power, and it's been surging at idle...

The fuel pump, cap, rotor, and plug wires haven't been touched... i haven't had a chance to hook it up to the scanner... no SES light has EVER come on.. Anyone seen this? For 203k miles i'm pleased that i haven't had to do a whole lot of maintance on it..

My big issues is the loss of power, which isn't terrible, just makes it annoying because i wouldn't feel comfortable towing heavy with it right now, and the surging at idle, other than that the truck starts right up, warm and cold starts, and i've never had any issues.

 

[someotherguy]

It was due for wires, cap, and rotor long ago. Buy only high quality parts. The crossfire style caps on Vortecs are notoriously crappy these days. Be sure to re-use your old cap screws, especially if the new ones have thread locker on them. Plastic distributor body on these are crazy easy to break the tabs off where the screws go. So that's why I say re-use the old ones and tighten them gently.

Remember while you're doing wires that they are NOT in numerical order. They're close, but not exact. The numbers are stamped on the cap so use it as a reference.

While you have the cap off try moving the rotor from side to side. If it doesn't budge, turn it, it may pop up a little, then try side to side again. If you get much movement at all, the distributor is worn and will need replacing. You need a scan tool capable of reading the cam retard angle, in order to set the new distributor properly - a timing light will not help you. Be sure to make 2 marks - distributor body AND rotor position, before removing the old one, so you can get the new one in as near as humanly possible to same position.

Your original injectors and fuel pressure regulator are likely shot but since that's a $400+ job just in parts, best to take care of the ignition first and see how it responds.

Richard

 

[JScott23]

You think it's cap/rotor/plugs/wires? Thats what my dad thought as well...

I do agree with him that if the fuel system is working, and the truck is never having hard start issues to just leave it alone...

 

[JScott23]

and i only plan on using AC Delco parts, i've heard that anything other than AC Delco is a bad idea

 

[JScott23]

Okay so i changed spark plugs, rotor and distributor cap... runs a little better still has no power...

I still think it's fuel related, possibly the MAF sensor? o2's? for what it's worth it cackles really bad when i'm up past 2500rpm... and you have to dang near floor it to get it to go past 2500 rpm... otherwise it runs through all the gears without going past 2500rpm.

 

[someotherguy]

So what's your fuel pressure look like?

Richard

 

[east302]

for what it's worth it cackles really bad when i'm up past 2500rpm... and you have to dang near floor it to get it to go past 2500 rpm... otherwise it runs through all the gears without going past 2500rpm.

Clogged cats?

 

[JScott23]

I'm gonna test the fuel pressure and run the diagnostic with our scanner over the weekend... Also cats could be getting clogged..

I'm thinking

1. Cats are Clogged
2. MAF leaning out the A/F Mixture
3. Bad o2s

or a combination of all three.

 

[JScott23]

So what's your fuel pressure look like?

Richard

I think i found the problem... fuel pressure is 40 PSI, and drops to 30, then creeps back up to 40 at acceleration. It's starving for fuel... pump is suppose to put out 60 PSI..

The cats potentially could be clogged as well, but a definite fuel issue.