1998 E-250 P1506, P1537, P1131, P1151, P0340, P0171, P0174

Van started very rough idle, very cyclic in sound. A few good strokes, then idles down (almost cuts of), then RPMs increase to normal for a few strokes. Scanner pulled 8 codes:

P0340-Camshaft position sensor A bank 1
P1506-Idle Air Control Overspeed error
P1537-Intake Manifold Runner Switch Open Bank 1
P0401-EGR Flow Insufficient
P1131-Insufficient Switching Control Valve Sensor/Lean
P1151-HO2S Bank 2 Sen1 Insuff. switching Lean Mean
P0171-System Too Lean Bank 1
P0174-System Too Lean Bank 2

Where would be the best place to start. Replace O2 Sensors, Clean MAF Sensor? EGR?

I assume this is a 4.2 engine having the P1537 code? Or is it a 5.4? As far as the p1506,1131,1151.171,174 I would check for a vacuum leak depending on what engine is in it is to the location of the leak. The MOST common place is the on both engines is the PCV hose elbow. Has the light been on for a while because the P1537,401 and 340 are not related to the others. If it's a 4.2 then once you remove the doghouse you should see a box with two rods one going to each side of the lower intake and probably will see one of then hanging down because the bushing is broke. Best to replace both of them.(THIS IS FOR THE 4.2 ENGINE ONLY) and this is for the P1537. The P0401 is MOST of the time a bad DPFE sensor or clogged passages. Again on the 4.2 engine for the P0340 the Cam sensor syncronizer are bad about seizing up and breaking the cam sensor and disrupting the signal.

Yes, it is the 4.2 Okay, I removed the air filter assembly and the MAF sensor. I cleaned the MAF sensor, since I had it off. I found a hole in the hose going from the air intake hose to the gasket cover on the right side of the engine. I replaced the hose and put every thing back together and got rid of the 1506, 0401, 0171, 0174. The rough idle is still there, I'll try to track down the broken brushings tomorrow. Thanks for your help asecmt.

Ok the 401 will come back that has nothing to do with a vacuum leak or the other codes. The DPFE is probably no good. If it still runs rough, look under the throttle body and you will see the elbow for the PCV hose and if the PCV valve is heated look at the right rear corner of the plenumn for hole in the line. What I am saying go over the PCV hoses with a fine tooth comb these are bad about spliting and is very hard to see. All the codes listed are very common on ford products. You still my have a problem with the cam sensor(P0340) and syncronizer. This will also cause it to run rough and stall. (no fun to get to either)

I will take a closer look at the PCV hoses while I'm in there tomorrow. I couldn't sit still tonight and went back out in the cold to see if I could locate the box with two rods, I couldn't. Can you offer a little more info on the location. I have the haynes repair manual and the photo of the cam sensor is unclear, it sounds like you have had to get to one of those before, where is it? I really appreciate the help.

On the rear of the intake you should see two bubble looking actuators. They should each have a rod coming off them and going to the intake. The bushings that attach the rods to the intake are bad about breaking, the rod may be gone but usually just the bushing fails. Easy to see with the "doghouse" removed. I said box earlier as ford makes a couple different styles of this setup. As far as the cam sensor goes its in front, on top of the timing cover under a water pipe, get my drift about fun to get too. It is a flat sensor that is attached to the syncronizer and this looks like the lower half of a dist. Yes I have done my fair share of all this you are doing..