Unknown rough idle and bottom

[russ2606]

I have a 99 tahoe 4dr with the 5.7 and it runs super rough. It used to be only going up hill from time to time, but now it’s constant. I fixed the p0102 with a new MAF
And p0440 with a new EGR. I also replaced the pcv valve and canister pressure relief valve. I’m at my wits end. It feels like a vacuum leak bou I can’t find it anywhere. I checked the T body, intake manifold, and all vacuum lines. I need help on this it’s my daily driver with all my tools for work.
Please help

 

[wjburken]

Welcome to the forum from Iowa.

Im not 100% familiar with the 5.7, but there are some basics that you should look at.

Have you changed or checked your plugs? What about your plug wires? What about your distributor cap? Do you still have your cat? Have you checked to see if it’s plugged?

Others will likely have other things to look at but those would be where I would start.

 

[OR VietVet]

Welcome to the forum from Oregon.

Seems like every time I turn around we see people with problems with the spider fuel injection system, like this: https://www.rockauto.com/en/moreinfo.php?pk=984604&cc=1353721&jsn=929

The checks that @wjburken has suggested should be done as well. The cap and rotor combo need to be looked at real good for any problems with moisture, cracks and corrosion. If unsure post some pics for us to see. Make sure the wiring inside the cap has no breaks or rub throughs. Any work done recently with the cam and crank sensors?


We recommend that you put all your rig(s) info in your signature so we all don’t have to guess at year, make, model, engine size, trans, rear axle locker…….etc. While you may have posted pertinent info in your first post, you may forget to do it again and the info is needed by us anyway. Makes it way easier on all members that attempt to help, to have that info right up front. It is also recommended that you take a pic of your RPO codes, on the inside cover of the glove box, and post that image in your signature. All this info will greatly help those that will try to help with a problem.


If there is any other info, like upgrades, mods or recent mechanical/maintenance work done, that would be helpful in any post as well. Too many times a question is asked by the poster and after about 10 responses we find out that the poster has done recent work to attempt to fix the problem or work that was done that SEEMS not related to the problem.

 

[avalonandl]

Check color on your plugs , 10 is good, if it’s oil filed or rich then they’ll be wet iand Black

 

[avalonandl]

Thats dupposed to be tan no ten

 

[OR VietVet]

Thats dupposed to be tan no ten

I was wondering what that "10" rating meant.

 

[Fless]

Check and monitor your long- and short-term fuel trims, see what they look like at idle and maybe 2500 rpm or so.

 

[96-2D-Hoe]

Have you changed the fuel filter?
Have you checked fuel pump pressure?
Have you cleaned up the battery terminals, cables and other ground points. Especially two grounds on the thermostat housing?
There's a vacuum line that controls the heater valve that if missing/damaged will create a vacuum leak when the AC is on.
There's vacuum lines / EVAP hoses running to the gas tank and back and also the gas cap if it's a smog truck like mine.

 

[Doubeleive]

what brand egr valve did you use?

 

[russ2606]

I was told by a Chevy tech to do what he called hard reset to drain the capacitors and it worked like a charm not a single issue anymore, runs like a champ now. But that scares me even more I’m not an electrically savvy