1998 Ranger v6 4.0L Weird running problem.

Ok, so I'm in the military and luckily we have a shop where we can do car work ourselves for very cheap. Lifts and such like that. One of my Staff Sgt's has a 1998 Ranger. He fills up the gas in the morning when he gets on base. Goes to work and parks it. At lunch time, he goes to start it up and it will turn over but it would die after about 4 seconds. First thing that comes to my mind is fuel filter. So I changed it. Wasn't it.

I then change the fuel pump. That wasn't it either, but now...It will turn over and stay running but it will run at an insanely low rpm. Really rough like. The engine will shake and such. Now I don't know what to do. I'm lost. I mean, I would have bet money that it was something with the fuel line, but now I don't think it is. But why would it all of a sudden start running (so to speak) after changing the pump?

Also, the gas pedal will not do anything to help it. It's almost as if the gas pedal is non-existent. It won't speed up the RPM but it will kill the engine by pressing it down all the way.

Please Help!

Marine19e3

Are there any engine codes?

Have you inspected/cleaned the IAC?

Well, there were no codes that came off, but when we hooked up a diagnostic computer, it immediately said that the mass airflow sensor was out of range. So we replaced it and sure enough, it runs like a champ. That was going to be my next step anyway. I've been reading posts on here and it seems to be a trend that 98 rangers have a sensor problem around this period in it's life. Oh well, it's fixed now.

Marine19e3

I have an 86 ranger 2.9 doing almost the same thing, but according to autozone at least it doesn't have an MAF sensor. I've already changed the fuel filter, and there's plenty of fuel pressure at the fuel rail. TPS seems fine, at least by this test: http://www.ford-trucks.com/article/idx/7/034/article/Testing_the_TPS_throttle_position_sensor_ECM_code_ 124.html. (http://www.ford-trucks.com/article/idx/7/034/article/Testing_the_TPS_throttle_position_sensor_ECM_code_ 124.html)
How do you clean the IAC? Is there anything else I can try before I give up and tow it to a mechanic?

You can check for trouble codes, only the OBD-II+ (95/96+) needs to have a special scanner. http://www.troublecodes.net

No, that engine is MAP with EGR. They made 2.9Ls MAF from 1990+ Califorina, 88+ MAP w/ no EGR, and 86-87 w/ MAP and EGR. I've converted my 88' MAP to 90' MAF.

You will not be able to go through the CEL method of the procedure, because I believe that model was not equipped with a check engine light. You will need a test light or an analog volt meter. There's better detail for that in a Hayes/Chilton's manual, but it's a simple process.

Your IAC is located on the top passenger side of the upper intake manifold "2.9L Electronic Fuel Injection". That's that cylinder shaped sensor, maybe about 4-5" long, should be the only sensor on that side of the intake, with a few wires running into the back of it. Get some break cleaner, spray into the sensor, shake it around, dump it out. Repeat until no black stuff comes out anymore. I've cleaned a few, it usually doesn't make a difference, but it's something to try. Run those codes before dumping any money into it.

Pete

Earlier today I found a howto for cleaning the IAC so I tried that, but it didn't help any. Where are the test connectors located on an 86? I have a haynes manual, but if it says anything about reading the codes I can't find it. I found a site when I first got the truck that said how to decode the light flashes, but I couldn't find where to find the connectors on anything older than an 88.