While driving on the freeway my 2000 explorer with the SOHC started cutting out. It finally died. I could restart it but it would not idle. Once I got it home I had codes P1131 and 1151 lean condition on the upstream o2 sensors. I erased the codes. Thinking that the fuel pump was shot I tested pressure and successfully pulled 65psi at idle. So far I have cleaned the IAC and the MAF sensor. It seemed fine for awhile but it started cutting out again in stop and go traffic. However, this time I did not get a check engine light. I noticed that my air cleaner box is slightly warped leaving a 1/16" gap about halfway down the right side of the filter. I am wondering if I am taking it too much air or contaminants from this gap. After applying a piece of duct tape over the gap and reassembling the air cleaner I went for a test drive on surface streets and the freeway. It ran fine without issue. I will take a short freeway trip tomorrow to see if it happens again. Will call AAA again if I have to. Anybody else experience anything like this? Need a solution since now I don't trust it and my 94 F150 only gets 10MPG around town...

 

It does sound like you probably have a vacuum leak. Even if the gap isn't the source of the hesitation, you don't want to be taking in air that is bypassing the air filter. Since that gap is before the MAF sensor it may not be the source of the issue, but certainly worth looking in to. Since it seems like the issue happens more once the engine is up to temperature, I'd be more inclined to thing you have a leak somewhere that heats up and cools down with engine temperature, such as the intake manifold gaskets, vacuum hose, or the PCV elbow.

-Rod

 

I agree that any intake leaks before the MAP will not cause any running problems but should be repaired. I just dealt with the vacuum leak problem. The PCV hose was rotten and the intake gaskets were leaking. I do not think these are your problems if it is happening after warm up and not when cold. That is exactly opposite of how those problems manifest themselves.

Your symptoms sound more like an EGR problem to me.

 

I have no problems starting it when cold. I replaced the upper and lower intake o-rings some time ago and have not had a problem with the cold-start vacuum leak since. I'll try testing the EGR. If I recall correctly the engine should quit when I apply vacuum to it.

 

Yep, the EGR should be closed at idle and if you apply vacuum to the EGR diaphragm, the engine should sputter and/or stall.

-Rod

 

So I decided to take it on a short 35-mile round trip. Started up in sub-40 degree weather: no problems at startup or idling. Went to Costco, ran great. Thinking about it during the drive I remembered filling a dry tank with cheap gas last week. The way it died previously on the freeway I think would be indicative of water in the fuel. That or I sucked up some gunk from the bottom of the tank. So with about a quarter-tank of the "bad" gas remaining I topped off with a bottle of Lucas fuel system cleaner and Chevron premium. Ran great on the way on the way home. Took it back out again on the freeway without issue. I'll drive it to work next week and see what happens.