Stumbling At Startup

1997ThunderbirdLXV6

1997ThunderbirdLXV6

PostWhore
Joined
Sep 22, 2023
Messages
1,922
Location
Richmond, VA
Country flag
Hello All,

This isn't a new problem, but one that occurred today for the first time in a while, potentially because it was the first warmer day in a while.

After much reading, I have an idea what might be going on, but I wanted to pass it by you all.

Situation:
  • I'm running several shorter errands around town; engine is warm; time between drives is anywhere between 10 to 20 minutes.
  • Tank is almost full; 30 miles since last fill-up.
  • At startup of the warm engine, I get significant stumbling/sputtering accompanied by a slight whooshing sound for about 15 seconds (best guess), which can be shortened by revving the engine a bit; then the idle gradually normalizes.
  • Today I actually turned the engine back off, and then I cycled the ignition a few times; each time the fuel pump primed, I could hear the same whooshing sound.
  • When driving off, everything turns back to normal, except during the first few seconds of initial acceleration, when I'm hearing a sound akin to tiny rocks traveling through a pipe; that sounds comes from the right side and seems to travel backwards (as if through the fuel return line?).

All this leads me to the conclusion that there's some sort of fuel vapor condition. There are no visible leaks anywhere in the engine compartment nor under the car, nor any fuel smells that I can tell.

Any thoughts or advice what I can do to alleviate this?
 
My 96 would stumble at startup for a few seconds randomly. Came and went over the course of a few months. Seemed to get better after a snap of the throttle, though not every time.

After a while the OG fuel pump died. Might not be a bad idea to check your fuel pressure just to give some peace of mind - bonus points if you can verify fuel pressure while it's doing its "dance".

Normal fuel pressure is 39 PSI less manifold vacuum pressure; at idle that would be in the neighborhood of 29-31 PSI.
 
O'Reilly's has them as a loan a tool. I've had mixed results from them though, many times they don't fit on the schrader valve well and either leak or won't read pressure.
 
1997ThunderbirdLXV6 said:
Fuel pressure gauge, is that something you can get as a loaner from the parts store?
Click to expand...
If you do get a loaner, be sure it has the schrader valve fitting. I bought this on Amazon ($25) and it comes with the Ford schrader valve fitting.

Actron CP7818 Fuel Pressure Tester Kit (currenlty out of stock)​


I bought another brand on Amazon and it did not have the fitting, had to return it. It was crap anyway. So be sure that if you rent or buy, it has the Ford fitting or you will need to go find one.
 
1997ThunderbirdLXV6 said:
  • When driving off, everything turns back to normal, except during the first few seconds of initial acceleration, when I'm hearing a sound akin to tiny rocks traveling through a pipe; that sounds comes from the right side and seems to travel backwards (as if through the fuel return line?).
Click to expand...

Is this a misfire sound?
 
Old thread reawakening. With ambient temperatures rising, this symptom is resurfacing.

I just got a loaner fuel pressure tester from Autozone. So correct me if I'm wrong, but I check for:
  • Pressure at idle around 30 psi?
  • Pressure at X rpm around Y psi? Please specify.
  • Pressure maintained after engine shutoff for Z minutes/hours?
 
1997ThunderbirdLXV6 said:
Alright...wtf.
The Schrader adapter from the test kit fits over the valve, but for some reason it doesn't catch the little pin. Unable to use this kit.
Click to expand...
Same issue I’ve had with those rentals. You can try another kit. I’ve had at least one work for me, but others not.
 
With our model of Ford, you will need the Ford fitting for the fuel pressure valve.

1744073046707.png

If I recall, the auto store loaners may not have that fitting and may not work on our model of Ford.
 
1997ThunderbirdLXV6 said:
The kit  did have that fitting, specifically designated for Ford. Still didn't work.
Click to expand...
:2eek:

Whaaaattt???? Get the f out of dodge....You do need to screw on pretty far to get a reading. And if my memory servers me, 9-10 people complained that the fitting broke either the first time or a few times after using it. So, it could have been a bad fitting. May want to give it another try from another store (if available) or just buy the tool. You can always use a fuel pressure regulator... :P

I know it pisses me off when I rent a tool and some SOB before me either broke the dang thing or left if filthy and it sucks to work with dirty tools.
 
I rented one from another Autozone today, and same thing. No reading. The kit looked new.

I was starting to wonder if the Schrader valve was stuck. So I attached the tester to my bicycle tire, and again no reading.

I'm just puzzled. I screwed it on as far as possible by hand. I don't want to use a tool; don't want to break anything.


Bottom line, I believe that there's something not entirely right. I'm not sure if it's the pressure regulator because there are no drivability issues at all. I'm more inclined to question whatever check valve exists in the pump.

When I turn off the car, I can hear noises from the fuel lines as if something trickles through for maybe 10 seconds.
 
You must log in or register to reply here.

Similar threads

Back
Top