'98 Windstar 3.8 Won't accellerate past 40

Had the transmission replaced about 2 weeks ago, and the manual lever position sensor replaced a week ago. New battery, tight connections, fresh fuel. The van sat idle for about 18 months waiting the cash for the transmission, but was started, limped around the block a couple of times and run at idle 15 to 20 minutes once per week. 141,000 miles on the odometer.

When cold the van drives fine, good accelleration, up to freeway speed, no hesitation, good shifting, maintains speed, averaging 20 to 23 mpg.

Once warmed up, 30 to 40 miles of continuous driving, accelleration drops off and the van won't get above 40 mph. Accelleration from a stop is long and slow.

One mechanic suggested a blocked catalyst, another a bad fuel pump. At one point we had the IRMC codes but they haven't reappeared since the transmission repair and I have driven it about 700 miles before this new problem appeared. No CEL, but the battery light has been coming on when the accelleration problem appears.

I'm soliciting ideas and suggestions. I am considering new plugs and wires and a new fuel filter (if it is easy to get to). Easy fixes first please, its still winter in Utah's mountains and I don't have a shop, or even a garage.

If the battery light is comming on, that is very likely a a connection to the problem.
Alternator, connection? etc.
I would get an "electrical system check", some auto part stores my do this for free.
YES....it is possible to buy a defective battery, and alternators can find strange ways to fail.
Another possibility is that something else is causing a serious load......problem is....things will likely check just fine, until the problem comes up.

The problem continues.

Replaced the fuel filter, poured in some injector cleaner as well. The van ran fine for about 35 miles and then while trying to accellerate up an on ramp it wouldn't go past 40 mph and then began to lose speed. With gentle pedal pressure the van eventually got up to about 60 mph. No CEL or other warnings. Accelleration is soft, shifting ok on surface streets after the van goes into this mode.

Checked the fuel pressure after replacing the fuel filter. All readings were within range, but on the low side, about 31-32 psi while idling and 41 psi idling with the fuel pressure regulator vacuum line disconnected.

Ideas? I really want to get this van running well after spending $2800 on a new transmission.

Latest up date: My son is driving the van about town at the moment and called to report that it has been stumbling/hesitating then died while at a stop light. Apparently on restart everything was going OK.:shakehead

More update: The van died 9 times in 40 miles, mostly highway driving. My son pulled over, turned off the engine, restarted and was able to proceed another 3 or 4 miles before the RPMs would drop off from 2,000 to 1,000 (or lower) and then the engine would die. Apparently the on/off cycle is resetting something that takes a few minutes before it kills the engine. Still no CEL.

So I'm thinking fuel delivery, air intake or exhaust systems, perhaps the Throttle Position Sensor? But why run fine for 30 or 40 miles from cold and then start acting up, and after getting the problem reset with an on/off cycle? :banghead:

Over the weekend I pulled the upper intake manifold to clean the EGR ports. I couldn't even see the ports, although I knew where they should be. Also noted that the lower intake showed the following: Starting from the passenger side, side toward radiator, the first two secondary ports showed rust scale, third port was just dirty, primary ports quite dirty with carbon build up. On the firewall side starting from the passenger side, the first primary port was heavy with wet carbon, the second port heavy with dry carbon, third port dirty. The upper intake manifold primary ports were all caked with carbon/ grease up to 1/8" deep in spots.

I spent several hours cleaning everything until it was factory bright. Before I put it all back together I plan to replace the plugs and wires as the back side is much easier to get to with the upper intake off.

Several questions:
1. With an engine this dirty (140,000 miles) what else most likely needs cleaned and replaced due to fouling, etc.?
2. Is the rust scale inside the secondary ports indicative of a gasket leak? No indication of the van using excessive water, no water in oil, no oil in water.
3. Will my efforts improve the drivability?

Thanks folks.

I have a 98 windstar with 142000 on it and several months back I had the same symptoms your son was having. It started dying after driving several miles....A new fuel pump solved the problem. Apparantly the fuel pump will also affect several other things cause the Dealer let me know that the MAF was reading bad. That cleared up after the fuel pump was replaced. My transmission was shifting hard, that also went away after the fuel pump was replaced.....don't ask me why it solved these problems, but at least I killed 3 birds with the same stone......

Sounds like it is clogged cat converter or a bad fuel pump. Since it happens after the van is running, it could be a bad fuel pump or a clogged fuel filter ... or a combination of both.

I'd look into a new fuel pump and a new fuel filter.

Thanks for the replies. A new fuel filter is in place, a new pump coming within the next couple of paydays (the van repair has to work around the payments for the new Corolla). :lol:

Hi,Replace the fuel pump .......Bye...