Solved My 1996 3.0L Aerostar drives like it's running out of gas.

[rv4fun]

My '96 Aerostar 3.0L is acting like it's running out of gas - threw a code claiming it was running "Lean." But I put a fuel pressure gauge on the fuel rail and it shows 30 psi at idle and when I press on the gas pedal, it goes up closer to 40 psi. It's so bad, I had trouble getting it back home from a block away! It was stumbling so bad, my speed dropped to almost nothing and I was afraid it wouldn't be able to make the slight rise on my street even at a crawl - then all of a sudden it caught and whipped my head back and seemed to be running great. That didn't last long though and now I'm having trouble trying to get over 20 mph. I haven't driven it much in the past 6-8 months and I have to take it for a state safety/emissions inspection before the end of the month to renew the plates.

If it's not the fuel pump, what else could it be?

 

[BrooklynBay]

What was the code number?

 

[rv4fun]

I can't remember the code and I've erased it now. It was something about running too lean which is exactly the way it acts - like it's not getting enough gas. As I drove up and down the street today with a pressure gauge tapped into the fuel rail, I noticed every time I pushed down on the gas, it acted like it wasn't getting enough gas and the pressure climbed from near 30 psi to almost 40 psi. Sometimes it can barely idle and other times it idles fine. Even though it wasn't running smoothly and stumbled badly whenever I tried to give it more gas. I'm worried about getting too far from the house and it getting as bad as it was last week when I started out to have it inspected. I guess I keep driving back and forth on my street (it's fairly level) and see if it will code again if necessary.

For some reason that I don't understand it's not getting enough gas. It hadn't been that many miles since I changed the fuel filter but I changed it anyway thinking maybe there might be some water causing problems. None came out of the old filter.

 

[BrooklynBay]

Clean the mass air flow sensor & check the coolant temperature sensor. Make sure that there are no vacuum leaks.

 

[Macgiobuin]

Forward Catalytic converter (one of them) maybe broke down and got blown down to the common downstream catalytic converter. After it stalls and then cools, or even unpredictably random, the powdered ceramic material falls down and suddenly you can run again. Separate the input pipe that goes into the downstream (common) converter, and if the downstream common converter is full of cat junk, that's your problem. But which one upstream failed? And why did it fail? Possibly a bad fuel injector, either stuck open (causing a rich condition, which the computer tries to fix by starving all 3 cylinders on that bank of fuel), or stuck closed, (causing the computer to think it is a lean running bank of cylinders, and tries to fix by richening up all 3 cylinders on that bank, which leaves 2 cylinders running real rich, causing the cat on that side to burn up and disintegrate.)

 

[rv4fun]

I think I'll start with the mass air flow sensor and the coolant temperature sensor. There may be a vacuum leak - after starts, it idles at a pretty high RPM for awhile before settling down. I've already replace the tubing to the charcoal canister under the air filter box. I'm busier than I want to be and don't know when I'll get to it. As a last resort, I may have to break down and take it to a local garage. Thanks for the advice!

 

[rv4fun]

BrooklynBay you nailed it right on the head! I bought a can of the CRC MAF Sensor Cleaner, gave it several good shots and blew it off with a little air to dry up the cleaner before reassembly. It started a little rough and threw a code P0171 "Lean Bank 1" before settling down. I let it run while putting everything away and then took it for a run up and down the street - WOW!!!!! I floored it several times and it never missed a beat! Seems like it's running like a champ again! I owe you a BIG THANKS! for your suggestion and if I ever see you, I'll buy all the beer you care drink!

Time to make another appointment for the inspections.

 

[BrooklynBay]

Thanks for the update! I'm glad that it was so easy to fix, and didn't require any major parts or labor. I'm not a beer drinker, but I'll take a can of soda instead. I'm going to mark this thread solved in green letters. Check the sticky thread on maintenance: http://www.explorerforum.com/forums/showthread.php?t=259038