Suburban miss fires after going up a hill?

[99subhelp]

I have a 99 chevy sub with the 5.7 and I had the seal replaced under the intake manifold and now it miss fires when I climb a hill and get to peak it will missfire badly. It will never do it when your climbing the hill or on flat ground but only when the engine has been enganged on the hill and then comes off of a little. It only happens at speeds over 50 MPH. I have replaced the plugs, wires, cap & rotor, and the fuel filter. The dealer wants to replace all these parts again and charge me 500 for it. I need some Ideas. I took it to another mechanic and he sees it misfire with the scope while driving but can't pinpoint it.

Thanks

Tony

[shearing]

Wow! you described your problem as if you have been driving my '99. I plan on cleaning the EGR valve via some shade tree advice this weekend. I will let you know what happens.

[ntwperformance]

what kind of wires did you buy? if you replaced them with the ones from advance or autozone take them back also check all the plugs to see if the porcelin is loose at the point where it meets the nut.i own a automotive shop i have had some bad experiance with advane and autozone wires.always use standard ignition or borg warner wires. the plug situation is somthing a ran across an a 1994 chevy truck a couple of weeks ago. i did a quick tune up on it and it ran worse i found the #3 plug missfiring around the porcelin.

[back2life]

guess where i got my wires from? its been missing since i bought it and the engines been rebuilt still the same but worse ive put plugs(ac delco),cap , rotor, wires, fuel filter on 3 times! oh yeh 1 o2 sensor still the same problem the longer i drive the more it stumbles and it has strong exhaust and ive checked egr valve seems to be working .

[RJN]

I have just experienced the same problem with my '96, 5.7 Sub.
I too just had the intake manifold seal replaced about 1,500 miles ago--seems like a pattern is forming. My Sub now skips, jerks and seems like it will stall (but never has) when going up even the smallest incline, and at acceleration when over 50 mph.
Has anyone in this thread, or otherwise, nailed down the cause?
Thanks in advance.
RJN

[ntwperformance]

do any of you have a check engine light?

[back2life]

i do not have a check engine light on nor do i have any codes shown.runs fine while driving just stumbles while idling or at a light.replaced my iac a few weeks ago it stopped working.seems to drag taking off ,maybe slow shifting trans originally suspected trans problem but some said engine was bogging down after having it rebuilt had the same miss as before and still shifts slow, goes into 2nd at 15mph or more depending on how fast i take off, 30 mph on 3rd.oh ive heard a rumor about cleaning up under the throttle body could this be true?have no vacuum leaks that i could find

[RJN]

Re: Check Engine Lights
Concurrent with the my sputtering/acceleration problem, my "Service Engine Soon" light came on and has stayed on since. I assume that the stealership will be able to track down an engine fault code; however, it is my hope that someone here will have some good insight for all of us.

I too have been told that it is likely the EGR valve. If so (and forgive my novice), but where is it located? I understand that giving the EGR a gentle knock may dislodge the carbon that is potentially clogging it.
Any thoughts?
Thanks in advance
RJN

[back2life]

it should be located to the left rear of the throttle body sort of circular in shape with a vac line going to it. ive already removed my and cleaned and reinstalled with new gasket still no change in performance. next project will be to remove throttle body and injectors and clean them but guess what ? the gasket set is kinda expensive to be so small! i wonder if it could be the fuel regulator anybody know how to check it? btw already replaced fuel filter twice

[matchew]

Well, this sounds too familiar too me as well and I have been told "sticky fuel injectors" I had them cleaned and it seemed to help for a while, but true to its nature the problem came back. $474 dollars down the tubes. It missfires as I crest a hill and will eventually go away, check engine light comes on and reads "random misfire" code. I would love to hear of any solutions as well, I am a thrifty Do it yourself mechanic, but this one is kicking my but. this is the first time in 15 years I have gone to a mechanic only to get what I thought, money taken problem still there.

[back2life]

i know what u mean,i very seldom pay someone else to fix my vehicles! damn near never only when i cant figure it out

[MSpring]

I have been having the same problem with my 1996 5.7 and changed all of the o2 sensors and it was still giving a code but no as often. I brought it to the dealer and they told me that it was a clogged cat. This is a normal problem because there is a federally mandated warranty for 8 years or 80,ooo miles and mine had 82,000 on mine. Guess what no warranty so I bouht mine at napa for 290.00 instead of 651.00 from the dealer.

[back2life]

Originally Posted by MSpring

I have been having the same problem with my 1996 5.7 and changed all of the o2 sensors and it was still giving a code but no as often. I brought it to the dealer and they told me that it was a clogged cat. This is a normal problem because there is a federally mandated warranty for 8 years or 80,ooo miles and mine had 82,000 on mine. Guess what no warranty so I bouht mine at napa for 290.00 instead of 651.00 from the dealer.

what did they do to it to determine it was clogged?

[Redonthehead]

Have ya'all tried a $5 can of Seafoam? Seems its a miracle tonic for all that ails an engine.

[back2life]

whats that ive never heard of it before?