Gents,

I've been battling the classic 'start then die' problem for over a year. I've replaced the IAC (about 6 months ago) the fuel filter, and the air filter.

The truck ran good for awhile, but it has started to die again right after starting. It's also running a bit rough at idle. There are no engine codes.

I removed the IAC and it looked pretty good. So after spraying it out, I re-installed it. I wonder how often these things go bad? Should I go buy another new one?

Next step is to clean out the throttle body and the MAF, but I'm open to suggestions. There's only a NAPA here, no Ford dealer or high tech auto shops. I'm a mechanic, but this crazy new stuff is impossible to troubleshoot without expensive equipment.

Thanks for any help offered.

 

Well ever since I got my truck I have talked to many different people about the IAC. As for me I think around 70,000 mi is when mine started to die when starting. I took the IAC off and cleaned it really really really well. Im talking better than I brush my teeth (Well you know) . I posted a thread not too long ago when mine started to do it.

Read: http://www.fordtrucks.com/forums/sho...d.php?t=252879

Some people tell me that when they clean their IAC it doesn't help and then they bought a new one and it made all the difference in the world.

On that link I gave you, at the bottom of the post I wrote out exactly what I did when I cleaned the IAC.

What I would do is try cleaning the IAC again (with brush, let is soak for a while in TB cleaner), clean the Trottle Body, basically everything from the IAC towards the air filter including the MAF. Don't forget about checking for any vacum lines that might have come off. They are very easy to miss.

Thats what I would do.

Bryan

 

I would clean the MAF first.

 

Well, I thought I had it fixed. I cleaned the MAF, and removed and cleaned out the throttle body. The MAF area looked clean to begin with, but the throttle body was full of carbon. The rest of the intake past there is bad too, but I didn't clean that part.

The truck does run better, and started just fine about a half dozen times. Then, it did the old 'start and stall' routine.

All the vacuum lines looked good. As did the elbow on the rear of the intake (from the PVC valve) which I also replaced a few months back.

Any more suggestions? Or, should I just replace the IAV again?

Thanks for the help.

 

Well, it would be a good place to start. Maybe you just got ahold of a bad IAC.

 

Well, I replaced the Idle Air Control Valve again, and the truck still dies at start up. I'm out of ideas...

 

is this a 5.4 or 4.6 ? what yr ?
if you feather the pedal can you keep it running?
How many miles on it ?
when you start it do all the lights light up on the dash (chk eng,abs,etc.) How did you chk for codes ?
If you have a scanner ,did you look to see if the Throttle pos sensor is changing as you open the throttle?
I've seen thottle pos sensors cause this ! but they usually throw a code ,thats why I asked if the light(chk eng light )was working

Rich

 

Hello,

The engine is the 5.4 liter version. Feathering the throttle doesn't seem to help at all. The truck will simply rev higher at first, then still die.

All the lights work at start up, so the 'check engine' light isn't coming on, but a broken bulb hiding the problem.

I haven't drawn any codes, as the CEL hasn't illuminated. I'd have to call around and see if a local shop has a code reader. There's no dealer, or Auto Zone in my town.

Is there anything I can check on the TPS physically, other than the connector?

Thanks!

 

I failed to mention that a stuck egr valve will do the same thing!
i believe you can measure 5volts with the key on at the connector for the tps
let me chk and get back to you.

Rich

 

At idle position, the TPS should have about .99v. 5V wide open.

 

Sitka (Gravis?),

I agree with FortyFords. If the EGR is stuck open (feeding exhaust gas into the intake at idle) it could cause a stall. Do a search on .... EGR* ....to find how to clean or replace it.

The TPS voltage would have to be WAYYY off to cause the stalling. With Key On Engine Off (aka KOEO) the TPS voltage should be between .985v and .999v. Under .98v or over 1.0v (+ or - .5v) is usually associated with hesitation on acceleration rather than engine stalling.

Good Luck,
Bill

 

Gents,

A new EGR valve is on order through NAPA. I'll be gone for a couple weeks so I won't be able to replace it till near the end of the month. I'll let you know how it goes...

Thanks

 

Say, during my research on EGR valves, I read about applying a vacuum to the valve with the truck running, and listening to see of the engine would bog down or die. So I did that, and the engine did in fact bog down.

I assume that means the valve is good and replacing it would be a waste of money and time. If that is right, should I look elsewhere?

Thanks

 

Sounds like it is working. It might be worth having the dealer hook it up to their WDS tool and driving the truck. It gives real live data as to what is actually happening. I may run about $80, but it's better than throwing parts at it.