Put on a new map sensor-4.1litre FWD fleetwood. Runs better without map hooked up but still dies when vac plugged into new map sensor. Barely drives. Any ideas?

When cold start is on will make more fuel to the engine for warm up. Only makes sense that even after warm up it's still putting the extra fuel into the engine that a heat sensor is bad. Namely the one connected to the MAP. Use your head, not the mechanics with all they're test equipment that are checking the wrong thing. You've put out a lot of cash because they don't know what to check for and are putting YOU through this. They're in it for the money pal. Not to help fix your problem.

Try Maf sensor,(Mass air flow)
Then try tps sensor, (throttle position sensor)
Unable to answer exactly without looking up codes

The map sensor measures engine vac. Can you tee the line on the sensor into a vac hose instead of mounting it ?

For this vehicle its one or the other you are equipt with a MAF (Mass airflow meter) and a MAP(manifold air pressure) you problem will be one of these sensor, Start with the mass air flow disconnect this sensor its at the air cleaner air duct with this disconnected you should be able to accelerate(but not that good) if you can then this is the problem and a replacement is in order, Now here the tricky part the MAP is a back up just incase the MAF fails it monitor the EGR, If you disconnect the maf and it runs better you will need a maf sensor.if you replace it with a known working one and there is no difference you have a MAP problem.

time to buy a new van.. umm what about the alternator?

you need to check the fuel pressure and the volume!!! next you need to find the tan and black timing est wire disconnect it if it runs better you need to replace the dist pickup coil

the power control module ( engine computer ) the ignition module, the rpm gauge if its an option on your dash gauge, ignition switch is all connected to the distributor.. In your car you will not have one for yours is a 4.5 fwd which did not have one. In fact 1985 on up were all electronic and were all distributor less. A coil pack sets onto a module which takes the place of the distributor. The camshaft and crankshaft runs off sensors that tell the computer what signal to send to the module when to have the coil add spark to the cylinders spark plug

Try checking Throttle position sensor with an ohm meter. Remove connection, put probes on pins (hit & miss on which ones, but you'll find 2 that give you a reading that increases as throttle is opened) and read meter as you open throttle all the way open & all the way back slowly & smoothly. The reading should go smooth up & down, If it jumps, or doesn't move at all in some spots, it's probably faulty. Have you tried to get any fault codes yet?

Its on the intake manifold, Click on this links and see a picture of the actual sensor. http://shop.advanceautoparts.com/ProductList.aspx?parttype=414&ptset=A&searchfor=MAP-BARO+Sensor Its has a 3 pin plug and a singe vaccum hose goes to it . Good Luck Sorry I didn't get back to you sooner,thanks for using FIX YA

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