Howdy all! Per my last post, I finally got my rear end all buttoned up and got my vehicle aligned and took it on the first real joyride since getting my transmission rebuilt and finishing the the complete front and rear end suspension replacement. The truck seems to accelerate fine at street speeds, a bit slower than I was originally hoping for, but once I hit the freeway I can only get to 70-80 MPH by fully depressing the accelerator pedal and even then the engine doesn't want to rev past 2200-2400 RPM. I did some reading on older posts regarding lack of power/low RPMs and know I've addressed many of the potential issues as the following parts have been replaced and components verified:

1. Accelerator cable was just replaced and confirmed that it actuates the throttle body ~90* from full close to full throttle.
2. Throttle body was thoroughly cleaned and checked for operation prior to installation ~2 months ago (new Fel-Pro gasket installed at the same time)
3. Installed a plenum upgrade kit from Hughes engines on the intake manifold ~6 months ago
4. Confirmed there was no oil (plenum leak) in the bottom of the intake manifold via an endoscope ~2 months ago
5. Replaced fuel pump assembly including filter ~6 months ago
6. Confirmed that fuel pressure at the fuel rail was within specifications ~6 months ago
7. Fuel injectors were thoroughly cleaned with fuel system cleaner and thus should be free of debris ~6 months ago
8. Oxygen sensors were replaced with OEM NTK ones and are operating correctly and not throwing any codes ~2 months ago
9. The vehicle has no stored or pending codes and passed CA smog ~2 months ago
10. The catalytic converters were completely replaced ~6 months ago
11. Vacuum lines and all associated components replaced ~6 months ago
12. When the transmission was rebuilt a new throttle control cable to the tranny was installed ~1 month ago
    1. As a note: It seems the trans likes to shift into 3rd gear at relatively high RPMS (2500-3000) and when it does it's rather rough, moreso than I'd expect from a freshly rebuilt transmission.
13. Quite literally everything else besides the driveshaft, rear differential, ABS control module, fuel line, brake lines, auxiliary power steering cooler, and brake booster have been replaced on this truck within the last year as I worked on it in my spare time.

However, after messing with the rear end and accidentally tugging on the ABS and parking brake wires a bit too hard moving the axle around, I do now have an ABS and parking brake light illuminated on the dashboard. I'm not sure if perhaps some safety system is kicking in and not allowing me to utilize the engine's full power as the computer thinks I don't have ABS (I do, I tested functionality last night so it is likely the rear speed sensor or the wiring, both of which I'll be able to verify tonight after work). Otherwise my only thought is that somehow I have clogged cats since I am more than able to rev the engine up to 4,500 RPM when in idle and the transmission in park, but they're brand spanking new and maybe have a cumulative 200 miles on them, in addition to the dozen or so times I started the engine during my original troubleshooting phase chasing down my emissions related engine codes which ended up being related to the oxygen sensors (note to anyone reading this in the future, just bite the bullet and buy the correct OEM NTK ones. Every single one on Rockauto does not like to work with these trucks). My other inkling of an idea is that it might have something to do with the freshly rebuilt transmission as I am able to get the engine to high RPM's while it isn't engaged, so perhaps a torque converter issue? Does anyone have any suggestions on what it might be?

 

Verify that you can fully open the throttle with the pedal. If the tv cable is adjusted to tight, you won't get full travel on the throttle cable. (from the pedal.) That's gonna require two folks, unless you have REALLY long legs.

Aside from that, I would suggest removing the front O2 sensor(s?), and going for a drive. (physically take them out of the exhaust pipe.) Go for a drive. Run better? More power? That would be clogged cats. And yeah, the may not be very old..... still need to check.

 

I checked that I got full travel on the throttle body by precariously placing my phone in the engine compartment and believe I have full range of motion. I'll have to try removing the O2 sensors tomorrow as the truck won't be cool enough to work on when I get back from work. In the event that it is indeed clogged cats, is there any remedy to unclogging them or do I have to go out and buy a brand new set? I just can't imagine that they've failed after such a short time on the vehicle, and they were extremely expensive (yay California!) to boot. Would clogged cats be the only real culprit?

 

I would wanna look down the throttle bores, and verify the butterflies are opening all the way.

I have to admit, clogged cats does seem kinda unlikely, given they haven't been on there long.... but, stranger things have happened. and your symptoms go well with clogged cats....

 

I peered down there the other month when I was messing with the throttle body and they appeared to open all the way (roughly 80* of movement or so, they weren't directly vertical but close).

In the event that it is indeed clogged cats, I imagine trying some cat cleaner/fuel additive would be my first step and then removing and cleaning (with compressed air/pressure washer?) would be the next prior to complete replacement? Thanks for all the assistance!

 

Depends on how bad they are. If they melted down, no amount of cleaning will fix that. And, if that's the case, I would be REAL curious WHY they melted down.... Did you see any oil in the intake when you looked??

 

No oil whatsoever, it looked as clean as the day I installed it on the engine.

I couldn't find the photo I took of the inside of the intake but I did find one from when I had to take the heads off to remove debris from a broken spark plug that fell into cylinder #1. There was a lot of carbon buildup considering this was only from the dozen times I started the engine and got to temp while trying to diagnose some engine codes. I forgot how bad they looked considering the lack of engine time so perhaps my cats are bungled afterall

 

That is running EXCESSIVELY rich..... either that, or burning a lot of oil. Either condition would eat your cats in short order. But, I would also expect either condition to set a couple codes.....

 

I believe it was a rich condition caused by multiple O2 sensor problems and subsequent codes; prior to swapping in the NTK's my exhaust smelled like raw fuel and the truck barely ran. Based on the fact that my oil level has remained consistent and the engine was remanufactured and installed with upgraded gaskets/seals I don't think it's oil. There was also a distinct lack of smoke coming out of the exhaust during this time.

I knew it could've damaged the cats I just didn't for one second imagine that less than half an hour of engine time could actually foul them up.

 

You wouldn't think so.....

Do you have a scanner that can read live data? Would be interesting to see what is going on when you try and accelerate at freeway speeds.