My ever so trusty '90 3.0 went on a trip from Huntsville, Al to Nashville, TN and back today. Didnt miss a beat the whole way...Set the cruise on 70 and cranked up the tunes. Only problem is that gas cost me $45!!!! It doesnt matter what I do, all i seem to get is around 10 mpg out of it...highway or city, easing on it or pedal to the floor...it doesnt matter. I have changed out the O2, the IAC valve, the TPS, it doesnt have a maf to change. The plugs and wires are fairly new, however the plugs are some cheap autolites..and the wires are autozone brand. Would these cause my crappy mileage? Or is there something else to suspect? The van runs VERY VERY strong and doesnt miss at all at any range..the idle is a little lumpy sometimes but it never stalls. The only code that pops is System lean right side...I only have one O2 so I guess that means that the engine is running lean. But how can it be running lean when it is sucking down so much gas? I havent changed out the fuel pressure regulator but the pressure is a steady 35 I believe. And there is no gas in the line. Any help is greatly appreciated. With the rising price of gas and my wallet being steadily depleated I would love to resolve the case of the missing gas. Also, what mileage is to be expected from my 3.0? Highway and city please...thanks alot.

-John

 

I'd be checking that fuel pressure. Just because there isn't fuel in the vaccum line doesn't mean it's not bad. Also check for vacuum leaks.

 

From your narative, it sounds as if the engine is staying in the cold start up mode, which permits a rich mixture and the poor mileage. Since you have already replaced the most common culprits the only two remaining sensors that would cause this would be either the engine coolant temperature (ECT) sensor or the air charge temperature (ACT) sensor. Both are fairly inexpensive to replace. Be aware there are two coolant sensors, one for the dashboard gauge (single wire) and the actual ECT which will have a two wire connector. The ACT is found on the intake manifold and looks very much like the ECT. The ECT fails more often than the ACT. Could also be either of those two sensor connections are loose, broken or disconnected. Since you have codes stored, don't forget to disconnect the battery for 5-10 minutes to clear the memory.

 

I would do a compression check also. Just because it runs steady does not mean a Valve or ring is not stuck..

 

Well, a single valve or ring could not cause that bad of mileage, unless there were other problems present. I'm thinking coolant temp sensor.

 

It has been stated here by myself, and others, that the Aerostar 3.0 V6 seems to run at peak effiency with factory Motorcraft plug wires, cap and rotor. Also, a good elctrical test might be in order, to determine the alternator is putting out peak power, Many poor mpg woes can be detected to poor spark at the cylinders. Plugs, either Motorcraft or Autolite platinums (same plug really) are recomended. Battery cables okay? if original, 1990, these might need attention. I replaced my original 4 guage cables with 2 guage cables with excellent results. Vacuum lines important. At the age of your van, from high heat conditions, cause them to either crack, become brittle, or soft. Soft hoses cause them to "suck in" causing a blockage condition. Then, with the engine off, they look normal. It's like sqeezing the vacuum hose with pliers, which cause performance problems. Just some ideas, good luck. With your front end properly aligned, tire pressures at optimum pressure, front and rear brakes properly released at factory specs (the front calipers fully released from the rotors. There is some "drag", designed in, but there is a fine line, if you understand what I'm saying) you should at least get 15-17 mpg with your Aerostar, at highway cruising speeds, generally flat terrain, IMO. ED

 

15-17 would be typical. If you lost one cylinder, due to misfire or something, you will probably get 14. Getting 10 could be a bad temp sensor. I doubt vacuum lines, unless they are "sucking in" at idle. However, vacuum lines are very inexpensive to replace, and frankly, I'd replace them anyway. If that coolant temp sensor has failed, the computer will stay in closed loop mode, and consume a lot of fuel as a result. It can be tested quite easily. And check the spark plugs, and make sure they look good. You could have a bad cap and rotor as well.

 

When my "93 3.0L O2 sensor failed, it indicated a lean condition. As a result, the PCM tried to compensate by pumping more and more gas into the engine, and the O2 sensor still reads "lean." Well, to make a long story short, it fouled up the plug, and I ended up replacing both the O2 sensor and the plugs.

 

I have a 93 3.0 ext 250 thousand on it just made a trip around 500 miles,made 24 against the wind and 27 with the wind

 

I would check the 02 again. ChinaZone , and the rest sell cheap 50% will fail junk!

I use Factory 02's that last another 10 years and are metering right!


One reason I rebuild with factory parts. I don't need to replace my starter or Alt or anything else every year.

 

Muffinman, right on! That's it in a nutshell, and the other responses were excellent. I also might add, if the 3.0 V6 Aerostar motor has run through several warm-up cycles running in a rich condition (faulty o2 or temp sensor) that will cause the cat convertor to overheat. When they overheat, more often than not, they melt inside (for lack of the exact technical wording) and cause a restriction on the exhaust. So what happens, is you think the engine is running fine, with new 02, temp sensor, new cap, plugs and wires, yet the engine is still working needlessly harder to overcome an exhaust restriction in the Cat. Point being, don't operate the Aerostar 3.0 too long, running rich, or cat damage can occur, especially in a higher mileage van. ED
PS 25+ mpg in an Aerostar is excellent!! I never have come close to that figure in my van, the most I ever saw was 17 - 18.5 highway (1987 XLT 3.0V6 CA Certified Van, which is probably THE reason right there! )

 

My 1989 EB 3.0 was getting 24MPG with 180k miles on it. Normal city driving was around 19mpg.

When my 02 went bad it ran fine and the only reason I found it fast was the computer showed a lean condtion and the roof mounted computer MPG went too 15 in just a few seconds.

 

I would repalce the 02 sensors as often as the maintenance schedule suggests, regardless of how long it is supposed to last. The cat is at stake here, and I'd rather keep it running in top condition.

 

I have a solid 35psi fuel pressure. The o2 was replaced less than 10,000 miles ago. I believe it is a bosch sensor. As for the cats, they are not a problem as i removed both of them a while ago.

 

Is this the same van the overdrive does not engage as per your earlier post?