2007 hummer h3x with about 53000 miles

I know I should go to a shop, but I am trying to see if anyone here might have a better idea of what is going on. I had been getting the catalyst system efficiency below threshold code. Ignored it for a little bit..Got some random misfire code, then a month ago as I was driving home on the interstate, I lost power and I drove to the side of the road. Cut it off and couldnt get it to really go over 35 mph. Basically was going 35mph at 5 rpm. for about 7 miles to be able to make it home.

I bought a magnaflow exhaust manifold, walker secondary cat pipe, 2 new o2 sensors, properly gapped the NGK Iridium IX Spark Plugs and also installed brand new coil packs as well. Just got it all installed and went for a test drive.. as soon as I got down the road and got closer to 35/40 mph it started to lose its power again and just rev.(it wouldnt go any faster and was just revving)

Does anyone here have any ideas on what this issue could be? Any help is def appreciated.

 

What do you mean by lost power? Are you getting the a "Reduced Power" message in the DIC? or........

are you pressing on the accelerator and the motor revs but the truck does not go?

If it is the second, your transmission is slipping, check the fluid level, color and smell. Might be time for a rebuild.

 

no message on the DIC. I am pressing the accelerator and its getting gas. I am getting up to around 35 mph..3 rpm i guess and then its just reving as I give it gas and not going faster than that. back in may I changed the transmission oil

Bad fuel injectors wouldnt cause this would it?

 

Remote Mount : 15 Row Atomic Cool Plate & Fin Remote Transmission Cooler Kit, -6AN

I did install this transmission cooler kit months ago too, but all has been fine with that.

 

The trans oil is down to the cold line at about 180 degrees

 

Symptoms sound like a clogged catalytic converter to me. The "walker secondary cat pipe"...I'm not clear on what you mean by that. Did you replace the catalytic converter, or just the pipe? The "honeycomb" internals of the catalytic converter can break apart, and then the pieces shift position and clog the exhaust flow. No matter how much throttle you give it, you wo't be able to get more than 2-3K rpms out of it. Take a block of wood and bang on the catalytic converter; if you can hear pieces loose inside, that's your problem.

 

the "Walker secondary cat pipe" this is the pipe that meets the exhaust manifold. I changed the exhaust manifold/cat and the pipe with cat after it.

 

I agree with Hawk on the symptom diagnosis. A quick way to tell if a cat has caused a restriction problem is to remove the primary oxygen sensor (the one closest to the engine). If the exhaust is badly plugged there will be an increase in performance. If the exhaust is partially restricted there should be nearly full performance restored. Your misfire code could have been caused by the cat starting to restrict flow. Also check your air filter. If you vacuumed up a leaf pile or other debris there won't be enough air flow. I'm not sure if there would be other codes with this or not but, it's an easy check.

 

I understand what you guys are saying. but thats what I am getting at. I changed all those parts days ago. I do see that the transmission fluid is down to the cold line when hot. and its a little bit darker in color. I had changed the fluid just months ago and I added an aftermarket trans oil cooler. Going to be my next step I guess in double checking all that.

 

My trans fluid took around 4 quarts to bring it up to the hot line. MAYBE after installing that new aftermarket trans oil cooler the fluids had to work their way throughout the system and it just wasnt enough.