Engine, tranny, power, mileage ...

[Moneymaker]

Hey guys, I've read previous post on several of these subjects...
I have been suffering from poor mileage for the last eight months,
I have an air raid staged 2 air intake. I have iridium plugs put in with new O2 sensors. Have a new thermostat. I did a resonator delete with a straight pipe to a duel tip exhaust. Back when I got the truck and have a random misfire code so I clean the throttle body replace the plugs. I just cleaned the throttlebody again and checked cylinders five and six for water condensation on the coil packs.

The engine idols smoothly with no problems. But seems to have lack of power and wants to downshift often.
at times driving down the highway the RPMs jump up and down, Which I've heard could be torque converter related?
The plugs come pre-gaped but after I take the truck in the shop for motor mount and get it scanned again I'm gonna pull all the plugs again and check them along with recapping them.
I did have the small hose under the airbox disconnected for some time along with my air intake gasket slipped off for a few months... Would this Vacuum leak cause my catalytic converter to go bad? I have a California only Cadillac converter and it's $4-$500 to replace is it also possible to clean them out with chemicals in the can?

I'm running 05 Isix LT. 96k. I have 30.5 inch tires on it and just put marks lift on it with new shocks

Thanks a bunch for your help in the past,
Any input would be greatly appreciated
thanks Jeff

 

[gmcman]

How long ago did you install the tires? The tires could easily cost you a MPG or two easy, let alone the lift. Did you perform a TB relearn when you cleaned it? Did you use the AC plugs? Where is your temp needle indicating when hot...straight up at 210 or at the very least 1 tick to the left of straight up?

 

[gmcman]

As far as the sluggishness, could be a slightly plugged cat, a backpressure test can indicate this.

What about this vacuum port here? Does it pull vacuum and is it plugged if it is pulling vacuum?

 

[Wooluf1952]

Welcome


In case you haven't heard:
http://gmtnation.com/forums/topic/218-welcome-to-gmtnationcom-heres-the-story/


When you check and/or re-gap the the plugs, be careful. Those Iridium pieces can crack off.

 

[kkoether]

Cam Position Actuator Solenoid! Pull the plug on it and check for oil in the plug. If it has oil in it replace it. I just went through this on my wife 04 Rainier with an I-6. It was shifting funny, getting poor gas mileage, and the performance was terrible. It wasn't throwing any codes just running like crap. It's relatively easy to replace and around $50.00 from GM Parts Direct.

P.S. I was also thinking plugged CAT. After the new solenoid all is well.

 

[Moneymaker]

Hey thanks for response...

Couple things to get on same page.
My 3inch lift was just put on last week, and these problems have been going on for 8 months. My tires are way older and didn't drop much gas milage when put on.

When I did clean the Throttle body I didn't disconnect the battery. I put a post up and this 6 months ago and got responses saying it was not a big deal and saying to do it again with the battery disconnected.

I have the AC delco plugs and run synthetic oil. I replaced the thermostat. It's just under 210 like it should be.

What's the throttle body relearn?
I will check vacuumed leaks and look up The solenoid.
Mechanic shop was closed this weekend so I didn't get to perform the scan yet but will update you shortly.

 

[Wooluf1952]

I think he meant a PCM relearn that you do when you clean the throttle body.
The PCM resets to factory specs by disconnecting the battery or pulling the fuses while cleaning the t-body. If you cleaned the t-body 6 months ago, the PCM will have reset by now.