In continuation of my previous thread, (https://www.ford-trucks.com/forums/1...ntly-dies.html) my issues with the truck stalling are still present.

Here's what I've done so far with success:

• Replaced 90* PCV elbow on back of manifold. Elbow was dry-rotted and collapsing and created a vacuum leak that made the truck idle high.
• Replaced IAC valve. Valve was not functioning as the truck would not and could not hold and idle when started. It would start and immediately die.

The issue I am still experiencing is a random/intermittent stall out when in Drive and coming to a stop. The issue appears whenever the truck is at operating temperature, moving forward, and then stopped - say at a stop light or stop sign - for a period of time longer than 15-20 seconds. The idle will be holding fine between 600-650 rpm and then just fall down and stall out.



Before replacing the 90* elbow and IAC valve, the truck had a surging idle. The engine would begin to shudder when dropping below 500 rpm and then kick it up. This happened frequently. Now the idle just drops off. One moment I'm at 600 rpm and stopped, the next moment it dies. No shudder and almost no indication it's going to die. It's that quick...


In attempt to help locate and replicate the issue, I sat in the vehicle with it in drive at operating temperature and had my neighbor and father jiggle all of the vacuum connections while I watched the tach for any changes. The only one we could seem to duplicate the issue was by disconnecting the top hose off of the air intake (right before the throttle body and butterfly valve) that connects to the intake manifold right at the IAC valve. I decided to replace the hose section on that line near the rear of the manifold. No luck.



Other than that, the truck does not have any problems cruising down the road. Fuel economy has not changed and it runs like a top when accelerating. No loss of power or any other indications. All other vacuum connections look good.


My next step, and this is where I want/need some input, is to use a can of carb cleaner and start lightly spraying the various vacuum connections and lines to see if I can cause a change in idle that would lead to the source. I realize I might seem convinced it's a vacuum leak, but I believe I'm on the right track to solving the issue.


If it's not a vacuum leak, then I really don't know where to start. I do not have a scanner on hand to monitor the running of the engine which might mean it's time to take it to a shop.


I'm all ears at this point. I'm stumped.

 

Might also spray the intake manifold gaskets.

Be aware that as you spray where there is a vacuum leak, the PCM will try to instantly correct for the extra carb cleaner being injested, so you have to have a keen ear.

Alternate method would be to make or borrow a smoke machine.

 

Regardless of what the shop did or says they did; carefully clean the small wire inside the MAF sensor with carb cleaner. If the wire is broken, or if you break it you will have to replace the MAF sensor.

 

Carb cleaner on the MAF? What about the specific MAF cleaner by CRC?

 

If you want to buy MAF cleaner feel free. I use carb cleaner since it's handy and never had a problem with using it.

 

OK, I was just double-checking. I didn't know if carb cleaner would be too potent/strong for the application.

Thanks

 

Nope, I spray it on, let it sit for half a minute, then blow it clean with compressed air. I keep the air nozzle back a bit to avoid placing too much stress on the MAF wire.

 

Just to run a thought by all of you:

Met a new guy, ASE mech by trade, this evening that had a scanner on hand. Once in the driveway the truck idled real low and the other it died. With the scanner plugged in, we went for a drive and I was able to get the truck to die once. The only thing he could bring up, at the time of stalling out, was a low reading on the MAF sensor. Once back at his place, he disconnected the intake to expose the MAF sensor. A simple jiggle caused the truck to idle low. He then tapped the face of the housing with the handle of the screwdriver and that action caused the truck to flutter and eventually stall.

At this point, is this a good indication of a bad MAF? Or, by exposing the MAF directly to outside air and not through the filter amplify the issue? Just getting some thoughts before making a purchase.

 

Yes a bad MAF or at the very least, the connector going to it is making an intermittent connection.

 

Sounds good. Your guidance and knowledge is appreciated. Will keep everyone posted in a few days.

 

Mine was surging, and would randlomly die at idle. They said it was the aftermarked IAC, and it needed an intake clean. When doing the intake clean they saw the mechanical fuel pressure gauge swing wildly, and now they are saying the fuel pump is bad. I have change the IAC and the MAF and had no change. Sounds like yours is the MAF. But just some info on what I am gong through now...

 

Good news. The issue is finally resolved. It was the MAF sensor overall. In a turn of events, it became clear that my MAF sensor was the culprit when I received a bill from my now ex-mechanic charging me for a MAF sensor replacement and a part number. The MAF is an aftermarket Delphi brand. As it turned out, once I received my Motorcraft MAF from RA, I saw that the resistors in Delphi were larger and the wires thicker than the Motorcraft part. A quick swap of parts and a reset of the PCM by unplugging the battery was all that was needed. The truck finally, after much hassle, runs fine using a Ford part. Go figure!

In summary, my message is simple: use OEM parts. Had I not received that bill with part number on it, I would have never known they swapped the MAF and my headaches would have been greater.

 

97ExpGuy,

Glad you resolved your issue!

Hmmm, maybe a good reason to ALWAYS check the box that says "Return old parts to customer", or at least tell your mechanic you want the old parts just in case.

 

You mean to tell me that guys who can afford to have a mechanic work on their truck get to check a box and have old parts returned?

 

Not only that, but they get to pay some guy 4x as much for something they don't need and get a lollipop too!