I have a 97 F150 Flairside with 171000 on a 4.6. Recently I was getting the Excesive EGR codes (intermitent) for which I did not immediately take it to Ford to fix. I was getting ready to do the EGR tests when the truck started to stall at stops (foot off gas, in drive and max air conditioning on). I also noticed that the truck would buck every now and then. This typically would occur on hot days, either at stop or coasting to stop. The truck would just die like someone turned the key off. If I tried to re-start right away it would not start for about 30 second (just cranking over). I took it to Ford and they said I had a bad DPFE (accounts for the 402 code) and that the IAC was sticking. After paying $450 which included diagnostics ($98.00 an hour), I picked up my truck. The next day it stalled. I brought it back to Ford and they could not get it to stall. I picked it up and drove it home. The next day it stalled 2 times. I took it back to Ford and they still could not get it to stall (however, they went back into the cpu and removed the previous 402 code that they were suppose to do). I picked it up and latter that day it stalled again. I took it back to Ford and this time it stalled in the service line while the service tech was moving it to the back. Yea verified that it still stalled (obviously not the IAC). This time they said that the CPU was loosing the signal. They said I needed a new CPU and garaunteed that if it still stalled that I would not pay for the CPU or labor. I authorized and the next day I picked it up. First day did not stall, however, the second day stalled twice. I took it back and it has been there at Ford for three days (they once again can not verify the stall). So until they verify the stall I don't get my money back for the new CPU that I don't need. The stalling occurs without warning at stops or coasting to a stop, when stalled the truck won't start for 30 or more seconds unless I turn the ignition off and then restart. I also still now and then feel the hard bucking. Not the fuel filter, changed it two weeks ago. Any other suggestions, anyone else see this problem, no codes generated. Ford has done complete diags and no codes. No codes generated when it stalls. I suspect fuel flow problem (pump, fuel cutoff, pressure regulater, etc). I have asked them to test for that; however, not getting any answers. This is the first bad issue I have had with the truck..

 

Just wanted to add the mods that I have had done to the truck...

Modified the exhaust - Converted to 3'' pipe from cats with a magnaflow truck muffler...like the sound - added 4 months ago

K&N Filter - I keep the MAF clean - Added over two years ago

Also, the switch on the master cylinder that is controled by the cruise control (controls the breaks when in cruise mode, I believe). Located on front of master cylinder. This switch leaked and shorted the connector. This also caused the break light fuse to blow and the truck would not start. Ford replaced the switch and said the connector was ok to continue to use. I just noticed that my cruise control does not come on at all.

I also noticed that a sensor at the rear of the transmission (next to the drive line connection) is oily and that none of the other sensors are oily. Suspect the sensor is leaking and I believe this is the speed sensor (Ford said this will not cause stalling).

Just some added info....

 

When was the last time you checked your upper intake plenum and throttle body for deposits?

http://www.fordf150.net/howto/throttlebodyclean.php

 

Have not had the assembly off in a long time; however, do keep it cleaned with Throtle Body cleaner and Injecter cleaner in gas... I have also used the Sea Foam in the gas.. Ford has recommended that the body be cleaned and the injectors cleaned; however, they apparently do not think that this is the problem as they replaced the IAC and the Computer. I would think that they would have said that it has to be done before they go any further, especially if they are to guarentee my money back if the computer did not correct the stalling.....

 

Hello, I would suspect the fuel pump.I had one on a Mustang that had an intermittent fault. It would just dye going down the road,it would also start back up and run for who knows how long and just die again. It got progressively worse where it wouldn't start (no fuel)I figured out that if i would bang on the tank close to the fuel pump the thing came on.Thats how i found my little problem. Wes.

 

dsanbeck,

Have them check the TPS (throttle position sensor). Check the voltage through its entire range. A bad or burnt spot on it could be causing your problem.

Good Luck,

Bill

 

Thanks for the feedback. I keep asking them if they have checked the fuel pressure and get the answer that they have completed full diag tests on the engine. They say they have completed all pin out tests (which I would assume TPS as well). Anyone from Ford out there that knows the procedure for a complete test (engine diagnostics). Would the TPS be checked and would the fuel pressure be checked? Again they are no codes produced even when it stalls....

 

I'd run it down the road with the WDS connected making a recording until it acted up. That should be part of their $98/hr (holy shi...er...money bags, Batman) diagnosis fee. Monitoring things like short and long term fuel trims, IAC activity, fuel pressure, injector pulse width, and fuel pump duty cycle.

 

Here is a post of possibilitys for the P0402 code...

https://www.f150online.com/forums/sh...ighlight=p0402

I will again tell you that the 4.6L engine is know to have deposits form in the intake plenum that can completely close off the ports to the EGR and PCV lines. You have a lot of miles on your engine so I would say to check the intake plenum for deposits just as a maintenance measure. I also agree with Wes that it could be a fuel pump problem.

 

Well,

They had it for three days - They said they road tested every day and it did not stall. I went and picked it up and drove one block and it stalled. Went back and this time the shop supervisor went with me...without the flight recorder. It stalled three times during our test drive. The supervisor got out and pressed on the fuel pressure relief valve and only a dribble of gas came out. He mentioned something about a fuel relay (not sure where this would be...on fuel pump maybe?). We went back to the shop and there it sits again. They are supplying me with a rental. So it is not the IAC for which I paid for. Not the computer for which I paid for and they now will have to reimburse me. How much does it cost to have the fuel pump replaced?

 

Ford called me back and say now that it is the Crank Position Sensor loosing a pip signal. Not sure what a pip signal is. They said that the loss of the signal should produce a code;however, on rare occasions it doe not. This would cause the stall at idle (lack of RPMs) and bucking at higher speeds (RPMs keep it going). $39.00 part with 2 hours labor. They are also putting my old computer back in and refunding my costs for the computer replacement (with a warning that it might go out because they found it to be a problem; however, it did not cause any problems as the stalling still occured). Will follow-up after I drive it for a day or two. It still could be wiring and not the sensor. This time they gave me no money back guarantee...

 

PIP...

"On pre-OBD II Ford applications, a code 14 is generated if there’s no crank position sensor signal, which Ford calls a "PIP" (Profile Ignition Pick-up) signal."

http://www.babcox.com/editorial/us/us80124.htm

 

We replace the Crank Position Sensor on my friends 5.4 in about 20 minutes and that included removing the fan belt because it was in the way. The sensor on the 5.4 was on the front side of the engine.

 

Looks like the sensor was the problem. Did not stall or buck all weekend, even when pulling my trailer. Noticed a sizable increase in power and cleaner shifting. Hopefully, this fix will last a while.