Getting really frustrated with this one! For about 2 years now, my 1988 F150 4x4 4.9 six has had an engine stall problem. This will happen when it`s 10 degree`s or 100 degree`s, usually after about 2-3 miles of driving. This always happen`s when de-accelerating, and doesn`t matter if I`m going 55 mph or 10 mph. Engine light will flicker on occaisionally also but will go out. If I give it gas, it will fire again and run smooth. Whenever I come to a stop sign, I can watch the tach go down as engine stalls, then give it gas and it pops right back up to normal. If I can keep the engine running till I`m stopped, it will sit and idle fine(about 650 rpm`s) although lately its beggining to idle rough! I have taken it to the ford mechanic 3 times and they cannot find anything wrong. The codes are always OK when they check them and the darn thing always runs fine for them!!
I did get a recall notice on the TFI module that states that the truck may stall at times but after reading more about it, it seams that this only happens when engine is very warm and if it does stall, it won`t start until engine cools down totally!! Mine will start up immediately after it stalls, even going down the highway at 55 mph. I just throw it in nuetral and fire it back up!! I cannot understand why no one can diagnose this problem?? I put a new EGR valve on it. I took the throttle body off and the gasket was just totally shot so put a new one of those on. Thought sure that would fix it but nothing. New plugs, wires,cap, rotor! HELP!!!!!!!!!!!!!!!!!!!!!!!

 

Have you ever cleaned the Air Bypass Valve , Its what controls the engine idle speed ? When you release the throttle it allows air to flow around the throttle plates . Since you have no DTCodes thats the first place to look when someone mentions a problem like you describe . It sits on top of the throttle body , Its a round cylindrical part that has a control solenoid , they periodically need cleaning with some type of throttle body cleaner .

 

Been a busy weekend. I will try this and let you know how it turns out.
Thank you......................

 

I'm not sure if the IAB is the same as on the 5.0L, but there is a adjusment plat that you can put in between the IAB and the TB which will allow you to adjust it if needed.

 

Well, I took the air bypass valve off yesterday and sprayed the heck out of it with throttle body cleaner. Also sprayed out the throttle body itself. Seemed fine last night. No problems!! Thought, cool, it`s fixed!! This afternoon, after work, I drove across town to pick my daughter up at school and my problem with stalling re-appeared. I would come up to a stop light and it would just cut out. I could give it gas, quick, and it would clunk and fire up again but if I didn`t give it any gas, it would die! This truck has an automatic transmission also so when it does die, I have to quick throw it in nuetral to start it again which is a pain. Any other idea`s???
Thanks,
oldenginejim

 

If it ain't broke.....change stuff till it is!


Take the Throttle Body off and clean it with carb. spray. also take and clean the idle bypass sensor out. you may also want to look at replacing the Throttle Position Sensor. It could be faulty and sending a wrong message to the computer. Try these and get back to us.

 

OK, I know it`s been a while but I am still having the same problem! Here is what I have done so far.
1. New EGR valve
2. New EVP sensor
3. Removed and sprayed the heck out of the AIR BYPASS valve with carb and choke cleaner.
4. New IDLE AIR CONTROL VALVE sensor.
5. New THROTTLE POSITION sensor.
6. New plugs, wires, cap rotor, belts, hoses,ball joints, tie rod ends,OIL PAN!!!!!(ok, I guess this stuff wouldn`t matter!)
How much more do I have to do? How much more money do I pour into this to make it run right? There has to be someone that has had this same problem somewhere!! I can`t get half way through town(2 miles) without it stalling everytime I let off the gas and start coming to a stop! I watch the tach go down, as soon as I see it start going down, I give it gas quick(with my foot on the brake of course) and it clunks hard and like it fires back up.
I let off again and it stalls. I put it in nuetral quick and it starts back up right away!!
I keep sticking the money into this truck because it is in such nice shape, it rides really nice, it`s quiet,it takes me anywhere, everythings nice and tight but this stalling thing is killing me!!!!
A mechanic friend still thinks it is something in the EGR ! Since it is a new valve and sensor, could it be plugged somewhere down below?? Man, any help in the right direction would be very, very appreciated!!!
Thanks...........
Frustrated oldenginejim

 

I had the same problem with my old engine. Could be one of a couple things, you might be getting too much backpressure... I had to cut my caty off on my '83 to get it to idle at all. Also, check your manifold. Friend of mine had a cracked intake and it caused it to run rough as hell, was putting to much gas into the motor and it washed all the oil off, not a pretty sight...

 

Hang in there, you'll find the problem. I would try the catalytic converter since you've done most of the other suspect parts. Have it tested (free) at a reputable muffler shop. Even if it checks out okay, I would try cutting the pipe BEFORE the cats and see how it runs. If problem disappears, time for a new cat...or you can just cut them off rod them out and then put them back on for appearance sake at inspection time.
Does it only die in gear? Doesn't act up idling in the driveway? Some folks have had missing/etc. problems due to the EGR system. You can always pull the EGR valve, fab up a plate to cover the fitting, bolt the plate on and see if the problem disappears.
Paying someone to pull codes is a b***h. Go to this site:
http://www.dalidesign.com/hbook/eectest.html
It will show you how to run your own code read out through your check engine light, using only a jumper wire. Invaluable information.
You may want to pull the codes right after it acts up. The ECM is supposed to store codes in memory, but I'd pull them right after the problem occurs. Also remember that after you find and fix the problem, you need to disconnect the battery cables for about 15 minutes to clear old codes from the ECM. Otherwise it may not realize that the problem is solved and still keep trying to compensate.
Another option is your ground wires. Find them and wiggle each one while the truck is sitting in the driveway idling. If it stumbles doing this, you may just have a bad ground.
I've run out of might be's. Good luck and keep us posted.

 

I keep reading this problem in differant forms. I would look at the Vaccum control valve. I found this to be the problem on my 4.9! It was causing the EGR to open at the WRONG times (Verry bad times)!

 

just food for thought, but i was told by my dad that when i start my truck whens its sittin for a while even 3 hours, i would have to left it idle for a while so the computer can get set. because if not the truck will stall if drivin even a few blocks. i dont know if this will help u, but who knows.....ive also been havin a problem with the vacum valve thingy 2...

"if its to loud, then ur to old"