Check the vacuum line to the fuel pressure regulator and the regulator itself. Either there is no vacuum at idle or the diaphram in the regulator is bad.

 

I have a 1990 aerostar 4.0 ext. I had not use the van for 6 months.It was stored in an undergorund garage. Today I was ready to use it again(for summer fishing). I started the engine which seems fine to me. Then I drove back home on the highway. After about 30 km, when I exit to city road and stop at a traffic light. The engine start to idle roughly and I try to give it gas but the van won't go. Finally it stalled. I then restart it and the idling is good. Then I drive a little while and the idling was rough again and it stalled finally.
I was about 10km from home so I called my brother to bring me a TPS and a MAF sensor which I got from wreck yard last week. I changed both of them but it didn't help. Then I decided to drive home and hoping to retart the engine as many time as it needs to bring me home.To my surprise, the engine didn't stall all the way except when I got home, I let the engine idle (just to test)and it happened again. I did the code test and i got 11,11,10,11,11. which means there is no fault code. On last December, I had a problem of hestitation during engine is cold. That is why I got those TPS and MAF sensors. I did check the coolant sensor with a ohm meter and it seems good.Please help and thanks in advance.

 

Thank you. I'll check it and post back.

 

Could be that the gas is bad from having sat for an extended period of time. Had the basicly the same problem with a lawn mower engine that had sat for the winter. It might just go away after you fill the tank again.

 

After re-reading the previous post, let me hopefully clarify what you are looking for. There should be vacuum in the line as the engine decelerates back to idle. Steady idle should produce the minimum vacuum reading. You should get the maximum vacuum reading when you suddenly open the throttle or suddenly close the throttle from a steady fast engine speed. So, be sure you check for positive vacuum by opening and closing the throttle, not just when at steady idle.

 

I kind of agree with aerocolorado. It could be a million things. I'm not what method you're going to use to check your fuel pressure regulator, I grabbed a handful of kleenex and when the van is running hold it by your exhaust for a few minutes, until your hand gets hot and then check what color the kleenex is. If it's black, there's a 60% chance it's your regulator. Is your van charging OK? Try resetting your computer. The last resort is to fill up your tank with the best gas and put a little bit of octane boost in it and then you will know if it was just from the gas sitting. Make sure you check your fuel filter. If it's the fuel pressure regulator, make sure you use the proper tool to disconnect the fuel line!!! Please post back when you figure out the problem.

 

[updated:LAST EDITED ON 23-Jun-02 AT 07:35 PM (EST)]Thank you everyone for the response.
Yesterday, i try to locate the fuel pressure regulator but I couldn't find it. May be it is located under the intake manifold on the ignition module side. Can someone tell me the location of the regulator and how to make it easiler to test it. First i will test will a kleenex. Also I call my friend who knows a little bit about car to help me but he does not know much about aerostar. He said usually if the fuel pressure regulator fails, it will give out black smoke because of too rich mixture and the exhaust of my van is not black. So we check something else.I told him what I have done like changing the tps..... He then looked for the MAP sensor but as far as I know, there is no MAP. He said there 's got to be one. After searching all over, we found a device on the firewall which look like a MAP but there is no vacuum hose attached to it. Then I refer to a 3.0 liter aeroster manual and it did look like a MAP. So we run a vacumm hose from the main vacuum to it and try running the engine. Like I mentioned before, it starts ok and idle fine at first. We were surprised that there is a MAP and it was not hooked up. ( I bought the van second hand 2 years ago, may be the previous owner did someting to the MAP or it is not needed for a 4.0 engine, I don't know for sure.) Well after strating the van, i test drive it, idling was a bit rough but it did't stall. I drove for about 20 minutes seems normal and thinking that the problem was fixed. When I got home, let the engine idle a little while to see. idle seems ok. Then somehow we kept the rpm at 1500 for a couple minutes, the engine starts to die. My friend said seem like one cylinder is not functioning (no gas to it)that causing the rough idle. I agree to that. Then seem like another cylinder quit and another and finally it stall. My friend suspect that the ECM is bad , could be the fuel pressure regulator or the igniton coil as well. Well, so much possible problem, I will check them all but which one to check first. I just come home from work. Will start checking after this post. I plan to get a ECM and a fuel pressure regulator from the wreck yard tomorrow. I cannot afford to buy from the dealer. Thank for the patience to read this post. It seems that the problem occurs after the engine is hot. By the way, I remember when I first start the van in the underground garage, the dashboard show CO, I wonder what that means. My van has digital display.

 

The fuel pressure regulator is behind the alternator. You have to take off the alternator, top radiator hose and the hose going from airbox to FI. Might be the oxygen sensor, you have more than one oxygen sensor, I think. Did you check your fuel pump? Fuel filter? Try filling up with premium gas? When you take off your fuel pressure regulator, you'll have fun if it's like mine. I broke mine off and you can't buy the clip for the fuel line without buying the whole fuel line. There is a special tool to take it off.

 

Just finish testing the van. I confirm I had the same problem. I start the engine with no problem, engine cold. Idle is fine. Drive it for 10 minutes and stop at my friend's place. Let it idle then engine start to rough and then stall. Wait about 20 minutes, can start engine and drove home. Got home, let it idle and same problem again. One thing is that after it stall, I turn ignition off and start it again and it will run. My other question is if the fuel pressure regulator is bad, why I can start the engine again after it stall? Getting dark outside, will take out regulator tomorrow morning and pay wreck yard a visit. Thanks.

 

I was just curiuos to see if you figured it out post back just a little tip clean your electrical leads to fuel-injector check your air filter

 

Hi doug:
Thanks for your reply.
I did not post my result yet because I wanted to test my van for a little longer. Last week I went to the junk yard and got a ECM and a ignition module. I try the ecm first because it is easier.It did not help. I didn't try the ignition module because to my experience it should not be it. If it fail, it usually misfire during cruising speed. Then I went to buy a bottle of octane booster and fuel injector cleaner. Put them in the gas and it seems runs better. So I try to run the gas tank empty but it still stalls when there is about 20 litres of gas in the tank. I had no choice rather to fill up the tank with premium gas. Now there is 20 litre of old gas and 60 litrre of new gas mixture in the tank. I also pour in a bottle of fuel infector cleaner. Having driving the van for a week, it does not stall any more.:-) I would say and I hope the old gas is the problem. Now, I had a ECM, an ignition module, a tps and a maf for spare.hehe.

 

I would have tested the fuel pressure first. The fuel pump can get quite variable when it starts to die.

Regards,
Al S.

 

Thanks for the reply. It turned out to be the fuel pressure regulator. The diaphram is broken causing fuel got suck in the manifold through the vacuum line causing rough idle and eventually stall the engine.

 

Did that problem cause your check engine light to come on?

 

Yes. The check engine light came on after the van being driven for about 15 minutes. The fault code is about the O2 sensor. That's why I changed the MAF and TPS sensors., etc. It also caused rough idling. As soon as I replaced the fuel pressure regulator, the idle worked fine and no more check engine light since then.