Help chasing down vacuum leak

[Bruce1978]

I have a 2000 ranger with a 4.0 ohv that I just replaced both heads due to cracks. Other than throwing 171 and 174 codes, and an occasional misfire, engine ran relatively fine, except for the cracked head symptoms (burned spark plug, losing coolant, etc). Truck has 159,000 miles. Used oem head and intake gaskets during reassembly, and tightened bolts according to sequence and torque specs. I read in some places people said to torque heads and lower intake together and others said that wasn't necessary. I tightened heads to spec then installed lower intake. Truck started right up but runs very rough. Frequent misfires during idle and sputtering and popping during a few short test drives. Also, didn't have much power. Hooked my code scanner to it and recorded live data, imported into excel and created a graph. Bank 1 short term fuel trim looks ok, but bank 2 is very high. Both long term trims look too high and have a large gap. Checked all of the vacuum lines and everything looks proper.

Someone on another forum suggest it could be the lower intake gaskets, which I considered my worst case scenario. Before I tear it back down, would like to rule out other possibilities. Was unable to attach the graph, but would like to hear any opinions. Thanks.

 

[ranger7ltr]

Simple question...

Are the spark plug wires on the correct plugs??? Are the plugs new and have you checked to see if you have a "dead hole"???And the injector plugs on the correct injector???

If you had a vacuum leak you would most likely hear the wheezing of extra air being sucked into the engine...

And I would probably check cylinder compression to make sure I had a functioning engine after the head swap...Leaky valves or rockers not opening or letting valves close would play into the issues you are having...

If you have an air compressor you can do a cylinder leakdown test to see if air or compression is not staying where it should...

 

[Bruce1978]

Ranger7ltr, new motorcraft plugs and wires. Wires are on correct places on the coil, according to the label on the coil. I labeled the injector plugs, so they are in the right places. Also forgot to mention I have new sealed power rocker arms and push rods. Good idea on the compression test. I'll give that a try.

 

[koda2000]

Todays vehicles have sooo many vacuum lines/hoses, vacuum motors and vacuum dependent emissions devices that it can be near impossible to find vacuum leaks without using a pressurized smoke test. If you want to find the source of your vacuum leak I suggest you take it to a good mechanic and pay his diagnostic fee.