Have been absolutely fighting with this 2004 D2. Got the misfires sorted, a new MAF, new upstream o2's, plugs, wires, coils, and new plenum gasket.

Drove it to work today, and have a pending set of codes, as the title suggests. P1171 and p1174.

I spent the better part of an hour looking for vacuum leaks somewhere, just using the old can of brake cleaner and seeing if it idles up. It was Inconclusive.

Unless anyone has any suggestions, I may just break down and take it to a shop for a smoke test. I can't think of anything else that would be the problem at this point, and I have verified that the new sensors are good, as I watch the values in live data, and they are all in spec. O2 sensors and MAF are functioning properly it seems. Good voltage, it goes up and down when it should, etc.

Perhaps of additional noteworthiness, is my short term fuel trims on both banks are full tilt 25%.

I am leaning toward vacuum leak.

Any second opinions?

 

if they are pending codes, then it might just be your ECU relearning metering with all the new parts.

keep driving and see what happens. even if the codes do go active, reset them and drive for a few tanks of fuel.

 

There are some good videos on making your own smoke machine for cheap. I’ve ordered parts to make one but other priorities have gotten in the way for me to put it together.
Vacuum leak sounds like a good place to start looking. 25% sounds like more than a pending code. Is it running in closed loop?

 

Full tilt STFTs at idle (when vacuum is max), then returning closer to normal while accelerating to get on the highway or up an incline (when vacuum is min) do indicate a vacuum leak. Maybe try blocking off the charcoal canister, if that solenoid has failed open it looks like a vacuum leak.

 

So I pulled the upper intake real quick, put some RTV all around, put it back together and it runs better.

But I still have p1171 and p1174 pending, along with now p0171 and p0174, so it is certainly running lean still.

Kind of at a loss now.

Short term fuel trim sits at the full 25% at idle/stand still, but then seems to fluctuate correctly while driving. I will share a video in a moment.

Any suggestions would be great. Thanks guys.

 

Given you had the upper intake off I am guessing it is a hose somewhere - brake booster, sai, evap, iacv, pcv, something. Did you do the pcv mod?

 

I have done no mods thus far. The intake is very well sealed now, with RTV and still have a leak somewhere

 

Video update

 

Did you remove the baffle in the valve cover? Recommend you do the pcv mod regardless of other issues. I can almost guarantee your vacuum leak is a hose- 90% chance. Injector orings really only other possibility assuming yor don't have a wire or folded gasket causing the upper intake to not be sealing

 

Any update? Have you done a smoke test?

You don't need to buy or build a smoke machine. I performed a smoke test many years ago on a friend's '04 DII using a rubber glove to cover the entrance to the throttle body (after the air intake tube was disconnected), a length of black tubing connected to the port at the other end of the upper intake where the SAI system connects, and a cigar.

It worked great, although after this many years I don't recall where the leak was that we found.

And BTW, STFT of +25% is not normal at any time.