I noticed fuel milage going down and an occasional stumble for a while but now im getting some black smoke more when I let off the throttle than when I going down the road if I rev the truck get all kind of black soot all over the floor otherwise runs fine idles fine the iac has been replaced air filter replaced check the fuel pressure regulator for any gas leaking into the vaccum line and its clean. any ideas? thanks guys

 

If it's blowing Black smoke out the exhaust, something is corrupting fuel trim & you should have a lit CEL & a trouble code clue/s stored in memory, so use your ELM scan tool to look for trouble codes & post up All code Number clues as they can help focus a trouble shoot. If you don't have a scan tool, or code reader, most autoparts stores will scan the computer at no cost if the CEL is lit, or we're having problems. Post All code Numbers found.
DON'T continue to drive it like this, as the extra rich fuel mixture will over heat the cat converters & cause them to melt down inside & restrict exhaust flow, cut power & cause the engine to over heat, all a vicious circle, so tend to this problem without delay.

 

I would put a gauge on the fuel pressure regulator. If it died, it may have jammed in the full on position, allowing full pressure. If it does, your fuel economy will be cut about in half. The regulator on the 90 Aerostar 4.0 was not an inexpensive part, and was hecho in Germany, to boot. Malfunctioning, 10mpg was it. Repaired, mpg went back up to near 20.
tom

 

I had an extra coil pack left over from the engine swap put it on yesterday and seems to be running better still get some black smoke when reving engine but no where near what i was getting .Maybe clearing converter? Pulled the cables to clear the cel and it hasn't come back on yet Still goin to shop tomorrow but maybe that fixed it. I'll post what I find out. Thanks guys

 

no scan codes ?????

 

No I don't own a scanner. I'm gonna have my mechanic scan it tomorrow

 

If you like performing your own diagnostics & turning our own repair wrenches, maybe consider coming by the inexpensive ELM scan tool running FOEScan or the like software on the viewing device of your choice as discussed here https://www.ford-trucks.com/forums/1...-scantool.html & have it scan All of the vehicle computer/controllers & post up All code Number clues it finds, as they can help focus a trouble shoot. It's Way less than most shops charge to do a scan.

 

OT, perhaps...

Pawpaw, you refer to that post regularly, but I have gone to various vendors on the web looking at their wares, and have heard of 'clones' that talks the talk, but do not deliver.
In short, could someone who has made a purchase from amongst the herd suggest a vendor that has a good tool. I think the item referenced is no longer available. Annnnd, the ELM chip maker has made a new chip with more 'features', though I do not have them in my brain to list. Not a complaint, but a request...
tom

 

Deeper into that thread I posted that seller BAFX on Amazon is recommended by the TCCA folks & a member here/in that thread, posted he has purchased from Amazon seller BAFX, after querying them about after sale support in case he had problems & they stepped up to the plate with an "E"mail reply, but I don't know if they sell all models, ie, WiFi, Bluetooth, corded UHB????.
If no replies here, the FORScan site has a forum you could query about known good sellers/brands members there have used.

 

When you removed the battery cables to turn the CEL off, it wiped the code clues stored in the computer memory.

 

Light came back on drivin to the mechanic he said the fuel pressure regulator was putting out around 65 and falling to around 35 after running for about 15 minutes so he's replacing it and the o2 sensors weren't reading right either I'll know tomorrow if it's fixed I'll post again when I get the truck back thanks for all the info

 

Make sure your mechanic understands the following:

1998+ Rangers utilize what is called a "returnless" fuel system. These returnless fuel systems have the following characteristics:

(1) there is no return line running back to the fuel tank from the fuel rail;

(2) they are designed to operate at higher fuel pressure...64psi (+/-8psi);

(3) the fuel pressure regulator and check valve are now located in the fuel tank with the pump assembly, not on the fuel rail.


So, the 65psi fuel pressure reading is good for your '98 4.0L. It shouldn't deviate from that number all that much, even at different RPMS.

Also on your '98 4.0L there is a something called a "pulse damper", located on the fuel rail, which reduces fuel system noise caused by the pulsing of the fuel injectors. The pulse damper is often mistaken for a traditional fuel pressure regulator, but it has nothing to do with controlling fuel pressure.

 

I think he wants to replace it because of the pressure drop after it warms up

 

The 15 min run period before fuel pressure dropped is about the right amount of time for a faulty non venting gas cap to have the fuel pump remove enough tank fuel to run the engine & pull enough vacuum on the fuel tank that the pump can't over come.
To test, run the engine until it stops, jump out & loosen the fuel cap to equalize tank pressure & see if the engine will immediately start & run. If so, put the fuel cap high up on your suspect list. It seems to take about 15-20 minutes of driving for an engine to use enough fuel to stall, If the fuel tank gas cap is faulty & not venting. Only requires 15-20 minutes of your time to run the test. More thoughts for consideration, let us know what you find.

 

Quick update on my ranger it turned out to be fuel pressure regulator and O2 sensors just got it back today went through 6 fpr's before they finally had to get the casting # off the old one and order one from ford running great now. I do have another question tho has anyone ever had trouble with a bad wobble for few miles after the truck has been off the ground it's a 4 wheel drive it does straighten out after a few miles