2000 2.5L intermitent start / idle problem

[HD_Slim]

This is a 5spd very basic truck no AC or CC. And it runs fine gets decent gas mileage. Has 113K miles bought it about three years back at 97K miles - at that time did a major tune up plugs - wires - etc.

About a month ago it began having random starting issues. Cranks - tries to start - dies. If I hold the gas pedal down a bit it starts right up. That worked for awhile, now when this happens it starts when I hold the pedal down but will not idle until the engine is totally warmed up. Meaning the temp gauge is sitting at mid position (had the thermostat replaced 6 months ago when it stuck open). And I can swear that a few times when the engine finally warmed up and I'm driving down the road I could feel a slight "snick" occur on the gas pedal as if something just engaged. And then all is fine.

I thought this was a cold sensitive issue but just last Wednesday it was 29 deg in the morning it started and idled just fine. Then I'm leaving work that same day its sunny and almost 50deg - will not start or idle. Very random and even if its not holding an idle it runs just fine no stalling or balking. Except it won't idle and just dies if I don't keep the throttle open. This now getting to be a dangerous way to drive.

I could start changing stuff but I'm a bit baffled. The check engine light is not on ---- I'm debating buying a scanner for $50 -- but if the light is not on would there be any codes ? Thanks in advance for any help. I've done many searches on the net and seen posts with exact issues but they never post on the solution.

 

[tomw]

IAC .. idle air controller. It is the gizmo that 'opens' a little throttle to provide the engine with air for idle speeds. It also bumps the idle for cold temperature conditions until the engine heats up, and kicks the throttle for power steering pump load, and increases idle for A/C compressor load if you had one. If it quits or gets gummed up, you won't get the increased idle rpm for a cold engine, and it will stall readily when cold, and possibly when warm if the throttle stop is backed out too far. Without IAC working properly, the engine idle rpm should be about 500 rpm, barely enough to stay running with any load.
You can test this by disconnecting the IAC and observing engine operation. If it runs exactly the same as before, from a cold start, it is likely inoperative. If instead it stalls more than before, the IAC may not be your culprit. It is controlled by the computer, and most use ECT and ACT sensors for coolant and air temp information to adjust the idle rpm.
tom

 

[PetesPonies]

You can get lots of information from a "good" scanner even though the light might not be on. But a cheapo scanner may just pull codes. You can even watch all the data live on 96-up cars, with a good scanner. But I would clean your TB and IAC well and reset the idle.

 

[HD_Slim]

I thank you much for the replies - time was of the essence as they say so on Sunday I took a shot at asking a certified Ford guy (CanadaFix) for $29 on Just Answer.com

Of course there are many posts on idling issues with recommendations from Idle Air Control - Throttle Position Sensor - MAF - fuel pressure - fuel filters - spark plugs/wires - inertia switch - etc. and I'm sure I missed a few.

He indeed recommended the Idle Air Control as a fix --- but the key info was that while the IAC is certainly controlled by the trucks computer it does not have the ability to trigger a code if it fails. Thus in my case the lack of any CEL even though this failure happened at least once a day for over 3 weeks. He indicated I could try cleaning the IAC but that yields mixed results (as I have seen here as well).

So for $40 at AutoZone I got a new OEM replacement - installed it on Sunday. Truck starts every time and idles stronger and smoother.

Back on the road

 

[PetesPonies]

Well, $70 isn't bad . . but we did say so for nothing