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3rd gen > all others
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IACV stuck closed? Leaking fuel injector causing it to run rich? Leaving off that hose should make the engine run lean in open loop (cold starting) and not start. Pumping the gas pedal should do nothing on a fuel injected engine. Holding the throttle wide open will shut off the fuel when starting, to clear a "flooded" condition. I think that is why you are having success with leaving the hose off to start it - it lets more air in so the engine isn't flooded when it starts. When the computer goes into closed loop, it can use the sensors to adjust the fuel mixture so that's why it runs fine when warm.

Also, check your fuel injector wiring harness for melted insulation under the black fabric cover. When wires short together, the fuel injectors stay on MUCH longer than they should, creating a "flooded" condition. This just might be your root cause. There is a stickied thread about it at the top of this section of the forum with everything you need to know.
 

3rd gen > all others
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First, does the check engine light come on when you first turn the key to RUN, but not start it (for the bulb check)? The one in my van is burned out, so if I have a code I wouldn't know it. 馃槀 If it does, then diagnostic system is working fine and we have a no code driveability problem.

Since it runs better with the PCV hose disconnected from the plenum, that means the engine is starved for air or running rich. Does it idle fine with the hose connected? If not, the throttle is choking off too much air for the engine to run, or the engine is getting too much fuel for the computer to compensate for. When it started and ran fine for the rest of the day, was that with the PCV hose disconnected as well? Makes me wonder if it just runs rich all the time, which could be a fuel injector stuck open (but would make it hard to start because fuel pressure in the rail would drop) or could be a saturated charcoal canister from overfilling the tank (engine sucks the vapors from this, and too much gas in it will make it run rich).
 

3rd gen > all others
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Does it drive smoother if you just floor the gas pedal? This is usually a quick test to see if the injector harness is shorting. They will run like crap at part throttle, sometimes at idle because the engine is using more gas than it needs due to the injectors shorted together. At WOT (wide open throttle) the computer goes into open loop and just dumps fuel into the engine, and if you're going fast enough when you punch it the WOT mixture is ideal and the engine runs perfect.

I had a friend's van act like this, a 2001 T&C awd Limited with the 3.8L. Their "mechanic" has already replaced the plugs, wires, coil and was stumped. The next thing he wanted to do was tear the engine apart and rebuild the heads! I looked up this problem on this forum many years ago, found out about the harness issue and got a good used harness at the junkyard for $5. Went back and we test drove the van, and it ran like crap except at WOT. I pulled the plenum and power steering reservoir off and replaced the harness. Yup, old one had melted wire insulation way under the black fabric sheathing, and bare wires were touching. Put it together with the new harness, fired it up and it purred. We took it for a test drive and it was back to normal. I told my friend to take the old harness to his "mechanic" and explain how it causes the problem, so that he could be educated and help others.

So we now know your check engine light works perfectly, and there don't seem to be any codes - yet. I think this problem can happen for a while with no codes. I know you said you checked the harness, but maybe it's just bad in a couple of spots and not shorting constantly yet? Something is causing it to dump in way too much fuel, when it's running, and the PCV hose being off is compensating for it by allowing more air into the plenum than the throttle body will allow (bypassing it). If it were a leaking injector, the fuel rail pressure would drop when parked and it would be hard to start without adequate pressure already in the fuel rail. You don't seem to have a hard starting problem, so I'm ruling out a leaking injector.
 

3rd gen > all others
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Did you OPEN THE FUEL INJECTOR WIRE HARNESS SHEATHING and inspect the wires under it, like a foot or so back into the harness (towards the injectors)? That is where the wires melt, out of sight. The proximity to the rear exhaust manifold and crossover tube bake the wire harness until the insulation melts and wires touch together, firing numerous injectors at once. Left alone, this CAN KILL your ECM (engine computer).
 

3rd gen > all others
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I had to re-read the original post - - 32,000 original miles??!! This thing is still a baby! I'm used to trying to diagnose vans with 150,000 miles or more on them. The fuel injector harness theory is looking less likely with that low mileage.

Is this van flex fuel? I think most 3.3L were of that vintage. Maybe something to do with how the engine senses what fuel you're running, and using the wrong tables for it? It takes more E85 to make the same power as unleaded gasoline. Might have something to do with the upper oxygen sensor, in how the computer senses what fuel it is using. I don't have any experience in flex fuel, but if the computer thinks it's running E85 and it's actually running gasoline, it will dump too much gas in.
 

3rd gen > all others
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I know from seeing handicap vans in the junkyards that they usually have custom made fuel tanks made from steel. Those vans are usually side ramp vans though, but maybe the rampway into the rear of the van still necessitated a custom fuel tank? If it is steel it could have rust in it, and it could be plugging a fuel filter intermittently.

I don't know how much I'd trust the onboard computer to keep track of the fuel mileage. It's more of a fun toy than something to use for precise measurement. Then again, if it's in a modified fuel tank...that info wouldn't even be accurate.
 

3rd gen > all others
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I guess I ignored the temperature relation to the starting/running problems. I wonder if the computer is seeing the proper engine temperature? If it thinks it's always cold, it will run too rich all the time and use gas. I can't remember if the instrument cluster and ECU both use the same temperature sensor? If separate, you will see the engine warm up but the computer won't and continue to run with too much gas, even in closed loop. Could be something that a scan tool could look for while running.
 
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