I just had the heads rebuildt and a new more aggressive cam installed at a reputable shop in houston. The engine is running great but every once in a while the engine will stumble at a idle and the check engine light will come on. It is pulling codes P1171 and P1174. I have new plugs, new 8mm wires, and a new coil pack on it. The shop told me that they thought it was the MAF but the one in the truck only has 5,000 miles on it. I know the new cam increase the valve lap but the shop I bought it from told me he had installed a good number of these and it didn't require a ECU reprogram.

After I drove the truck a few hundred miles I went back to the shop and he reset the computer but it still is kicking the codes. I had to drive the truck home to NC this week and only got 11MPG while towing a small trailer with about 500 lbs in it. Before the codes pop I get great power but afterwards it seams to lag alot. Aspecially when going up hills,

I am going to check for vacumme leaks tomorrow and will let you know what I find. The truck has 170K on it but I have invested a huge amount of money in it keeping it running. Basically everything is new under the hood. Radiator, hoses, MAF, heads, O2 sensors, All gaskets, rear main seal, water pump, plugs, wires, coil pack, and timing chain.

 

I'm not sure there was a question in there.

But you are getting codes saying that you're running too lean after having someone put another cam in the truck. Sure, you can and probably should go through and check the pressure at the fuel rail, etc but.....why? Bring it back and tell the guy he did it wrong.

 

So, both banks are running lean. When you installed the new MAF, did you buy another Bosch with matching part numbers or an after market one, what sort of air filter are you using, paper of K&N type and have you checked to se if the o-ring is still attached to the MAF?
If you don't find it soon, have your shop do a smoke test to find a vacuum leak.

 

Checked for vacumme leaks last night and didn't find any. The MAF is a OEM unit from AB, checked the O ring and all of the connections and they are good. The Air filter is a papper one from AB also.

 

My money is still on a vacuum leak.

 

Ok, maybe I didn't check the right places.I hit all of the intake connections. And the two hoses that come off the left of the intake. Where else should I check. Additionally I noticed the shop removed and blocked the two coolant hoses that go to the intake. Is that a good or bad thing?

 

The shop by-passing your throttle body heater without your permission is a bad thing.
The throttle body heater is there for a reason, it is also a known common leak but is cheap to DIY repair.
That will not have a effect on anything except the engine in the winter time if you live in the cold.
The valley pan gasket is a place to check for a vacuum leak.

 

Is there a way to check the valley pan basket without taking the top of the motor off?

 

Yes and no, with the engine running and using a can of carb cleaner spray around the valley gasket and see what happens to the rpm, they should increase when it sucks in the cleaner.
You can also use a spray bottle with water, if the rpms drop it sucked in the water.
If you use the water method dont worry, you wont suck in enough water to hurt anything, as long as you use a spray bottle that is, like a Windex bottle or your kids squirt gun, not a Super Soaker though, just a standard cheap squirt gun.

 

OK guys, I went all around the valley gasket with a can of carb cleaner with a nossel extender so I could be around the upper pendullem. I saw not change in the RPM. What else can I check?