Rebootdc

I have a 2000 3.8L V6 Windstar, that gave me the following error codes: P0171 & P0174. I have read the threads about the codes. I have replaced all 4 of my O2 sensors, new EGR Valve & Gasket, new fuel filter, but to no resolve with my problem. I even bought a new MAF sensor but when I installed it, it did not resolve my issue so I took it bakc for a refund. (those things are expensive). The van idles fine but when you engage it on drive it bucks like a horse and even backfires. I don't know what else to do. There are no visible leaks, I'm thinking a vacumm hose that I can't see is loose or something. Any help is greatly appreciated. Fellow Air Force member.

Tony.

LunaticSVT

I would take a look at your intake manifold gaskets as the source of the vac. leak. The 3.8L is notorious for this problem.

Unregistered

I have had those codes and fixed the problem. I have pictures of the whole procedure and the OSB that was sent to the dealer.

Unregistered

Those codes indicate a lean condition and when both codes are present, means that the O2 sensors are not at fault. Two sensors are not likely to fail at the same time. On my 98 Windstar, 3.8, the rubber boot on a vacuum line, on the top of the plastic intake plenum had cracked. That allowed enough air to cause the fuel air trim values to go out of range (At idle). At larger throttle openings, this leak was not a major problem. The engine ran well. If yours runs poorly when the revs are up, I would suspect a larger intake air leak.

mmcavinue

Does the engine idle if you disconnect the wiring connector to MAF? If so I would suspect a vacuum leak. I had the same problem with my 95 Windstar with the 3.8 engine. I too suspected a bad MAF and replaced it but no change. I found that the o-rings on the fuel injectors had dried out and were leaking vacuum directly into the cylinders. You can test this by taking a rubber hose (heater hose) and hold it near the injector and listen to it with the engine running. If it's leaking you'll hear it hissing like a banshi. To replace the o-rings you need to pull the upper intake manifold. Good luck!