Stalling on acceleration after stopping.

[mpsjr]

I have a problem with my '99 Eddie Bauer (5.4l). After slowing down, it will usually stall if I try to accelerate before coming to a complete stop. For example, if I am approaching a red light, and slow down to the point where I am about to stop, and the light changes, when I go to speed up, the truck will sometimes stall. It idles fine, and will accelerate without any problems from a dead stop. In fact, if, in the situation I described above, I come to a complete stop, there are no problems with accelerating/stalling whatsoever. There are other times it stalls as well. If I am slowing down because of someone turning in front of me (or if I am slowing down to make a turn), and then go to take off again, it will do the same thing. It will happen very predictably, anytime I slow down to under 10 mph and then accelerate without completely stopping. Very rarely, the engine will die and I have to shift into neutral and crank it back up to get out of the way of traffic. It always cranks right away.

This problem started around October of last year (2011) after I had to replace the fuel pump and filter. I have since installed another new fuel pump thinking that it may have been the problem, but that did not help (the fuel gauge on the new pump was bad anyway so it was a good enough excuse to replace it). It also does this no matter how much/little gas I have in my tank.

At this point, I do not know what the problem is. I would suspect the IAC, but as I said, it idles fine. It also has no problem accelerating from a complete stop. I also thought about the TPS, but did not want to replace it without asking for help here first. With the combination of braking followed by immediate acceleration, I would also suspect a vacuum problem, but have NO IDEA of where to even begin looking for something like that. I figured someone on the board might have experienced similar issues, and it never hurts to ask. Any help you guys can give would be greatly appreciated. TIA.

Matt

 

[DR3W]

That kinda happens to me when im below 1/8 tank. I think iots just my injectors spitting out gunk from bottom of tank when im low. But idk, thats just what mine does..

 

[hahnlsquid]

Fuel picks up from bottom of tank regardless of the amount of fuel in the tank....so IM sure that's not relevant....
I would check all vacume lines and replace the fuel filter as a start....also clean mas and run some seafoam in the gas and break booster lines...if this don't fix it id put a fuel guage on the rail and see how long it will hold fuel pressure after shut down.....might be fuel pump/fpr going bad

 

[DR3W]

I stall below 1/8 tank. Because of no gas! Im empty at 1/8 and dry when lite comes on.. hah

 

[mpsjr]

Fuel picks up from bottom of tank regardless of the amount of fuel in the tank....so IM sure that's not relevant....
I would check all vacume lines and replace the fuel filter as a start....also clean mas and run some seafoam in the gas and break booster lines...if this don't fix it id put a fuel guage on the rail and see how long it will hold fuel pressure after shut down.....might be fuel pump/fpr going bad

I'm not sure where all of the vacuum lines are. I tried seafoaming my engine after it started doing this and it didn't make a difference. The fuel filter was changed with the new pump, but I ordered a new one yesterday, along with a new TPS (Motorcraft) that I hope will fix the problem. If not, I'm going to change the PCV and possibly the FPR. The MAF is very clean, so I don't think that's the problem.

 

[mrford60]

i guess that you dont have a check engine light on, even tho your maf looks clean if you run a air filter that is oiled (resuable) the oil from that can coat the little wire in the meter and cause problems. there is a spray cleaner for that. also try cleaning out around your throttle blade with carb cleaner and a Q-tip.

 

[02expi]

sounds to me like the trans is not downshifting properly, staying in a higher gear and killing the motor when u take off with a rolling start. just my 2 cents worth.

 

[mpsjr]

i guess that you dont have a check engine light on, even tho your maf looks clean if you run a air filter that is oiled (resuable) the oil from that can coat the little wire in the meter and cause problems. there is a spray cleaner for that. also try cleaning out around your throttle blade with carb cleaner and a Q-tip.

I have a standard filter that is clean as well. I am beginning to suspect the IAC or FPR, but definitely think it is a fuel/air problem. My new TPS and fuel filter should be in by the weekend. Hopefully it fixes the problem.

sounds to me like the trans is not downshifting properly, staying in a higher gear and killing the motor when u take off with a rolling start. just my 2 cents worth.

It will still do the same thing even if I manually shift to 1 and repeat the rolling stop/acceleration sequence, so that can't be it. Thanks for the suggestion though.

I have been trying to pay attention to everything when this happens, checking idle speed, the speed of my truck, etc. There is no significant drop in RPMs prior to it stalling. In fact, when I initially go to accelerate, it actually will for about 1/2 second before stalling, and stalls for about the same time before picking back up.

 

[stamp11127]

Easier to diagnose through elimination instead of throwing parts at it. Do you have access to a fuel pressure gauge and code reader, specifically one that captures data?

 

[mpsjr]

Easier to diagnose through elimination instead of throwing parts at it. Do you have access to a fuel pressure gauge and code reader, specifically one that captures data?

No, I don't have access to either, but wish I did. Despite that, these parts are cheaper than buying diagnostic tools on top of whatever parts might need to be changed. It is my experience with problems like this is that you can take it to a shop and end up doing the same thing (throwing parts at it), while racking up a big repair bill in the process. $55 total for a new Motorcraft TPS and fuel filter is manageable, and is a gamble I am willing to make. $200+ for a code reader and fuel pressure tester without changing any parts isn't. I am willing to spend around $100 total on parts that I can change myself while trying to correct the problem, but that's about it. The truck isn't worth putting a ton of money into anyway.