Running Sluggish after Tune-up.

[95TahoePA]

Hows it going?
I have a 95 Tahoe (5.7L) and it recently just started running really weird. Let me start from the beginning: She ran fine since day one of me buying her back in Feb of 2011. Alittle hesitation when first leaving a light, but actually hauled @&!. 2 weeks ago driving home from work I had to speed up a bit to merge with traffic and she started to "pop" real bad like she was missing on at least 4 cylinders. Let off the gas and she was fine when I eased into the throttle. Move any harder then that and she "popped". Ok fine, Plugs, wires, cap & rotor needed to be done so I did them. Plugs gaped all to spec. Now, she has NO power from idle to 2500rpm in all gears... and still she is a bit sluggish.. Also, I full throttle it while moving, she misfires once and takes off like a bat outta hell. If I slowly ease into the gas, she pulls the power like she should. almost like she is being held back or hauling a airsteam trailer behind her. So, naturally, I check the firing order (yes, I know its 18436572) and thats right. Cleaned the EGR Valve (in working order) cleaned the IAC motor (only very minimal carbon on it, still was shiny). Brought the motor to TOP dead center, re-time it as best as I can without a timing light, still runs the same. Replace the fuel filter (gas in old one ran out clean). Even checked the old one with some gas from a gas can to see if it may have poor flow, but it flowed fine... Still replaced it. Checked all lines and injectors for clogs and they were fine. Found a vacuum leak at the throttle body gasket to the intake (TBI stamped on the housing). Replaced the gasket and still runs like she's hauling something. After a few mins of running, she gets worse. No smoke of any color out the tail pipe. Oil is fine & replaced not to long ago (within 5k and 6 months) Trans fluid is fine and not burnt looking or smelling. Deferential fluids are fine. Im at a complete loss!
Any suggestions would be appreciated!

Thanks,
Josh

 

[Donnie Yukonie]

i know it sounds stupid but is everything plugged in? and snug . I.E crank sensor ect..
did you check for spark on all cylnderS? maybe bad gas? throw some fuel additive in there

 

[gpracer1]

Have you ever replaced the O2 sensor?
If over 80K miles, replace it.

How does it drive if you start it cold in the morning and immediately drive without warming up?

 

[95TahoePA]

Body has 249,*** on it. Motor, exhaust and rear replaced/rebuilt at 190K. Trans was done at 170,000 (paperwork & receipts came with the Hoe). Been double and triple checking the plugs all the time just to see if I missed something. O2 was not replaced by me, but was done when the exhaust was done according to the receipt for that.

As for starting cold, or even warm, she starts right up, no issues. Used to idle at about 900-950rpm Idle.. Now idles at 500-600rpm in park. Drops down 400rpm.

 

[Donnie Yukonie]

thats a high idle! did the idle drop when you did the tune up? 5-600 is more like what you should have it

 

[95TahoePA]

thats a high idle! did the idle drop when you did the tune up? 5-600 is more like what you should have it

Yes, the RPM dropped into the 500-600 range when tune-up was done. Before it was around 800-900 when in park warmed up.

I will doublecheck when I get home to make sure im not messing up the RPM speeds.

A quick quote from one of my friends who tried to help out "it sounds flat."..

 

[gpracer1]

Body has 249,*** on it. Motor, exhaust and rear replaced/rebuilt at 190K. Trans was done at 170,000 (paperwork & receipts came with the Hoe). Been double and triple checking the plugs all the time just to see if I missed something. O2 was not replaced by me, but was done when the exhaust was done according to the receipt for that.

As for starting cold, or even warm, she starts right up, no issues. Used to idle at about 900-950rpm Idle.. Now idles at 500-600rpm in park. Drops down 400rpm.

190,000 for an O2 is waaaay too long.

 

[Donnie Yukonie]

190,000 for an O2 is waaaay too long.

lol guess thats next on my list mine are the origionals and im at 193xxx

 

[95TahoePA]

190,000 for an O2 is waaaay too long.

190K is when everything was done including a new O2 when the exhaust from manifold to tip was replaced.. Im sure the O2 sensor was done before hand. She now has about 249,000 on her.

 

[95TahoePA]

Ok.. I went over everything and found that the RPM's where around 600-700RPM's when at idle with the old stuff in. Had to really look at the cluster to get a better idea. But she is now at 500-600rpms in idle in park. Drop it into gear dead at 500. She sometimes will go down to 400.
In park and hitting the gas she sounds fine.. No hesitation so it only is happening when it's under load.
New problem:: leaving a light yesterday, I hit the gas gently and she pretty much stalled out... RPM's dropped to 0-100 heard no noise from motor or from the exhaust (radio was off so I could listen for anything) until I took my foot off the gas and she idled fine! Again, gently got into the gas and she slowly started to go until 2K then she ran fine.
This happens in every gear if she is below 2K there is no power at all.