Misfiring, runs like crap in morning

[Cpurp31]

1999 5.7 ppv.
Changed cap and rotor plugs wires and at times it will run like total garbage missing a backfiring.
Other times at 55mph and up it will almost studder or hesitate for a second
Plz help

 

[exp500]

Any codes?

 

[Cpurp31]

I’d say so smh

 

[exp500]

Any P0300's or P1345?
Have you updated the engine grounds? You are running two posts now. Coukd be connected.

 

[Cpurp31]

Sorry I’m a noob but, two posts?

 

[OR VietVet]

Vacuum leaks? Cat convertor problems? O2 sensor problems? Did all those codes come at the same time?

 

[exp500]

Post #5- Not sure that issue fixed yet. Could be connected.

1999 ppv hard for it to turn over/voltage drop

I’ve replaced the started 3 times on this and it is a pain in the ass for it to turn over if I had recently just shut it off and try to start it back up. Also when going around 55mph+ it seems like it misfires or hesitates from time to time. And occasionally when I’m driving it will run like...

www.tahoeyukonforum.com

 

[Cpurp31]

I think it could be connected. Idk if the ppv’s came with a push button start but this one has one. I’ve ran new wires since then. I’m going to check body grounds tonight

 

[Cpurp31]

Vacuum leaks? Cat convertor problems? O2 sensor problems? Did all those codes come at the same time?

Yea all codes came at same time. Could be a vacuum leak. I’m just hoping it doesn’t have anything to do with injectors

 

[exp500]

Add a can or two of berryman. See if it cleans up the injectors. You already have the updated spider.

 

[Cpurp31]

Add a can or two of berryman. See if it cleans up the injectors. You already have the updated spider.

Put some Berryman in. Ran good for a bit then right back to the same thing

 

[exp500]

Do a Live Data scan on a road test, should show you whats goin on. If thats not possible change cap/rotor and coil wire.
P0300 likely. nice to see graphing of codes or fuel trims, other sensors that live scan picks up when missing.

 

[YukonGTmaster]

This may seem like a no brainer, but how does your air filter look? I’ve seen those things soaked in red K&N juice.

 

[Swagfu]

Mine was running so bad that it wouldn't start sometimes. I would go out in the morning and it would crank like crazy and not start. Go out about 1 and it would fire right up. Changed the crank sensor and cam sensor and now it starts right up every time. Was driving me crazy. Maybe something to condiser.

 

[exp500]

Fuel pressure test with long hose.! Key on eng off #/time till it drops 10#. Driving#. And When missing#. Book is 62-66#