I am trying to track down a vacuum leak that has been causing me to get P1171 and P1174 for quite some time. After a cigar smoke test I saw smoke coming consistently up from underneath my plenum and approximately in the space in between the banks. I couldn't see any specific exit point of the thick smoke.

If you look in the picture, it seemed that it was coming from behind the sensor with the two green dots in the center of the shot. This leads me to believe it is coming from somewhere beneath the IM...

Any thoughts? I appreciate the help in advance.

 

Use Brake Kleen and a straw to spray your injectors while it is running. Be very deliberate with your sprays you should be able to hit 1-4 . See if it causes your engine to idle down. If so it is likely the injector orings which seal the injectors in their ports. Had a month long battle with these codes and after doing O2 sensors, maf, purge valve and inspecting and resealing valley gasket this is what I came up with.

 

Hey DiscoDubs,

I just tried the brake clean technique. I never heard the engine actually idle down, but after I did it twice (I wanted to make sure that I hit the injectors) the exhaust became very acrid, thicker and more white than normal (reminded me of a mini seafoaming).

... I would think that this implicates that the brake cleaner seeped into the cylinders around the injectors and that my injector o rings are faulty and need replacing... What is your opinion?

 

New injector o-rings sound like a good place to start. Its hard to tell in the picture where the leak is, but your valve cover gasket might be leaking or the 2 inside valve cover bolts may have come loose a bit.

Things to think about:
1)You might want to just get a new plenum gasket and throttle body heater gasket while you have the upper intake manifold off if they have not been replaced before.
2) If you have SAI then it makes the job 3 times more difficult. (a crowfoot wrench is your best friend)

good luck

 

It seems as though the orings may be the culprit but as mentioned replace
Some of those other gaskets while you have it all apart. The hardest part is prying the two SAI brackets off the side of the plenum. They are also an issue putting it back together and lining everything up. The injectors are easy to remove once plenum is off, just 4 screws and unplug from wire harness. No need to disconnect fuel there is enough play. I cut the olds off with exacto. Slide a towel under the fuel rail to cover the ports so you don't drop anything in there. Then just reseat the injectors once replaced. It was night and day on mine.

 

You should do wired and plugs also while it is apart. All together it's about 3 hours for your first time doing it.

 

Thanks for the great info.

Luckily:
1) I don't have SAI.
2) I already replaced wires and plugs
3) I have replaced the throttle heater plate and its gasket recently.
4) I already have the 12 pt 8mm 1/4in drive ratchet fitting

So, I will need new valve cover gaskets, a new plenum gasket (is this the same thing as the intake manifold gasket...?) and new injector O-rings.

Anything else I should replace or clean while in there?

Thanks again!

 

I had a vacuum leak in the same area that was from the injector O-rings. Gold coast Rovers had a great deal on the replacement O-ring (.58) vs. the other vendors which were like $6.00 each.

 

Your so lucky not to have the SAI. That should really shave time and effort off the job. Have you done head gaskets on the truck yet? If so that upper intake manifold (between plenum and upper intake) and valve cover gaskets would have probably been done then. I almost wouldn't worry about valve cover gaskets unless they appear to be leaking. Even so, the loose bolts are most often the problem as opposed to bad gasket. There is like 3 other owners posting problems with the same codes right now, let us know how it turns out.