Howdy folks.. me again.

About 4 months ago, I replaced head gaskets (and even gasket-matched, opened up all the ports, cleaned everything for 3 weeks, made everything pretty) and everything was running beautifully for about 5 weeks. Then changed out all 4 shocks. After changing the rears, I drove it around the block, turned it around and backed it into the garage to change fronts.

All I removed was the air box, MAF, and purge valve. That's all! Changed the shocks, put everything back together exactly. Truck hasn't been running right ever since. It struggles to get started, especially when hot. But then runs just fine in Drive. Smells really rich though. And always in closed loop after warm-up.

I'm getting 1179,1177, 0300, 1316, 0420, and 0430 consistently. Just recently changed the plug wires, again, for the 4th time in 2 years. Replaced breather hoses also.

I bought all 4 o2 sensors and a new y-pipe w/ Davico cats from rockauto[com]. Delivered yesterday. I know I'm not supposed to replace the cats unless all other issues are resolved. But with these codes, I'm not sure exactly what's wrong.

Can someone please, help shed some light?

Thanks,
Robert

 

Double check all the sensors and plugs related to the MAF, air box, and Purge Valve. Maybe you lost the O-ring for the MAF?

 

Good point fish, but yes I already checked all those. Even popped the rivets on the MAF, pulled it out carefully, cleaned it real good with sensor cleaner, replaced o-ring with new one, and then sealed it back with machine screws.

Short of replacing the MAF all together, any other suggestions I could look into?

Thanks again!

(EDIT: I checked fuel pressure today, when running it was steady 28 lbs.. turned off motor, and it immediately dropped to zero. UH OHH.. is this my fuel injectors or pressure regulator? I struggled finding a good fitting hose after head gasket job until recently.)

 

Check fuel pressure regulator vacuum line. Check intake manifold bolts are still to spec.

 

Thank you ihscouts, that line is brand new and fits perfectly.

But something to note as well, when I took the top end all apart, there were no gaskets between upper/lower intake and plenum chamber. Is there supposed to be one?

I found this gasket. It goes between the lower and upper stacks, correct? But what about between the upper and the plenum chamber cover?

 

I found the thread about rebuilding the VSS. Did that yesterday. Oh it was an EASY fix. Codes P0300 and P1316 went away!

Still have 1177, 1179, 0420 and 0430 though. I don't want to replace the y-pipe just yet until I know all other issues are resolved first.

Thanks everyone for any and all replies and suggestions.

 

I believe he meant the large diameter o-ring between the maf and airbox.

 

Oh! Umm, I had no idea there was supposed to be an o-ring there. Never saw one in the 300 times I've taken that thing apart..

It does sound like there is vacuum leak when I crank the truck up until about 30 seconds later it smooths out.

And another note... p1177 and p1179 codes came back the next day

 

Then again, it shouldn't matter since the leak would be before the MAF and would only introduce dirty air, not un-metered air.

It really does sound like your CATs are bad. I'd try replacing the O2 sensors first since you already ordered them. In some areas you can just remove the CATs and weld in some pipe, but you already ordered those too.

 

Thanks Eric... I found an o-ring that fit. The cold crank "whistle" is now gone. Hmmm...

Yes, I have all four o2 sensors and the new cats. I will change all those out this weekend. And also, I think I have an exhaust leak as well. Right before the muffler, around the weld, there's a bunch of soot built up. Could be half my problem, too?