Still losing idle

[jaycin]

Hello again folks,

After letting the 93 XLT sit for a week or so because I couldn't get it to idle (it would start and hunt for a few seconds and die), I tried again yesterday and it idled for 30 seconds or so before conking out. I'm on a very slight incline when parked but the tank is 2/3 full.

I went out again today and it started and idled for 90 seconds or so. Am I correct to assume the pump is probably OK? Then I checked the throttlebody. Very clean. I pushed the flap to see if it was stuck --- not stuck but extremely hard to move open.

Started up again and it ran at 900 rpm for 5 or 6 minutes. But died again. While it was running for this period I could here a clicking sound similar to an A/C compressor low on freon but not near as loud.

I'm going to check the IAC valve tomorrow. Could it be making the sound here? Would appreciate your input if you think it might be something else I should check. THANKS.

 

[MrShorty]

Am I correct to assume the pump is probably OK?

Based solely on what you've given here, I don't think I'd make that assumption, yet. Put a fuel pressure gauge on it and see what the fuel system is doing when it won't start/conds out. If the fuel pressure is above 25-30 psi when it conks out, then I'd say the pump is probably ok. If the fuel pressure is dropping off when it conks out, then the pump might be suspect. The symptoms you describe sound like what my pump does when it gets too hot.

 

[Roadrunner777]

Agreed, a fuel pressure test is really about as easy as it gets, and a basic gauge is under $20.

 

[jaycin]

MrShorty

What about the throttle? Does it open and close with acceleration? Should it be so stiff when pushed with your finger? I tried to take the controller off to exam it but the phillips screws are rusted and difficult to loosen. I'll try WD40 or something.

I appreciate your inputs.

 

[MrShorty]

[/quote]Does it open and close with acceleration?[/quote] If I understand correctly, then, yes, the throttle plate should open and cause the engine to run faster.

Should it be so stiff when pushed with your finger?

I don't know how stiff "so stiff" is. It should open fairly easily, but the springs on it should offer some resistance and should pull it back closed readily.

In addition to fuel delivery problems, I could see your symptoms being caused by a dirty throttle body or a bad throttle position sensor (TPS). Are you getting any TPS (or other fuel control) codes from the computer? TPS is a basic potentiometer and can easily be tested in the vehicle with an ohmmeter and a wiring diagram.

 

[jaycin]

Roadrunner777

I attempted to get on the fuel regulator today to test the psi. But I couldn't locate it. Please tell me precisly where to look and exactly how to test it. Thanks.

 

[Roadrunner777]

I'm assuming you found a gauge, you can call a shop and ask for a pressure gauge for fuel injection. The port: stand front center in front of the open hood. The large silvery casting on top is, of course, the upper intake manifold. Now, look down below the left edge for a metal pipe about 1/4" diameter coming out of that side and going nowhere. It may have a cap on it, it may not. That is your fuel injection test port.

The port has a shraeder valve, like a tire, so when you connect to it, you automatically open the port to the fuel rail. The system can be pressurized when you do this, you may get fuel spray/leaks, so be careful. Turn key to on, no start, and note reading. Run the engine for a while and note the reading. Post back here. I forget what spec is for this, I'm going to go look for it.

The fuel pressure regulator is back under the intake manifold. I'm not sure it is even visible without crawling around on top of the engine. The test point is not there, so you may not need to deal with it.

By the way, have you tried resetting the engine computer? If not then disconnect the battery for 30 minutes, reconnect, and drive a variety of conditions for 15 minutes. This will cause the engine to relearn the idle points.

I was looking for a spec and found a complete thread with pictures of the port and everything. Go here please:

http://www.explorerforum.com/forums/showthread.php?t=170334

One thing, the write-up is for a year 2000, which uses higher pressure. Yours should be 30-40 psi.

 

[MrShorty]

Here's the thread for the older fuel systems (it is also a sticky in the under the hood forum) http://www.explorerforum.com/forums/showthread.php?t=142801

 

[jaycin]

Thanks to both of you. I got to look for the fuel test port today but could not locate the tube you referred to, Roadrunner777. So I followed MrShortys' suggestion and read the 142801 pages. Great stuff. Then I went back to the xlt and there was this small (1 1/2in) straight port with a schraeder cap right next to the regulator.That tells me that is the pressure port.Too dark now but I expect to see a bicycal valve there tomorrow. Appreciate your time.

 

[jaycin]

I'm slow to fix this. Glad I have another source for transport.

I connected the gauge to the fuel pressure port. One turn of the ignition key shows 38 psi. Since I replased the o2 sensors last year, I am now examining the IAC. The ohmic value across the pins of yhe iac shows zero (KO). I have a similar iac valve (E715) that shows 20 ohms but its from a mercury. I think since both are E715 part numbers the ohmic value should be the same. Your thoughts please.

 

[Roadrunner777]

IAC troubles can be mechanical, that is, the valve itself is clogged up with junk. I would suggest removing the IAC (2 easy bolts) and inspecting the inside for grime. Also, be sure the valve shaft moves back and forth (opening and closing the valve). If you decide to clean it, they say to keep the solvent out of the electronic half.

I cross checked the Explorer IAC to one from a Mercury Sable and it did not match. I would suggest going to a site for auto parts and looking up both, see if they end up being the same part number.

 

[jaycin]

The IAC is very clean and the shaft moves quite easily. I know that selinoids (sp?) have very low resistance but I'd like to know what I should expect from a working IAC.

BTW, I cleaned the MAF about two years ago. Do you think that these idling problems I've been having since then might have dirtied the MAF again?

 

[Roadrunner777]

Somebody asked me to try something last week, and it might help here too. Try running with the IAC connected and disconnected. See if there is a difference.

You could look at the MAF, it's a 2 minute deal...