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4.0L starts and dies within seconds without riding the accelerator

spirograph

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Vehicle Year
1993
Make / Model
Ford
Transmission
Manual
Edit: Just took the OBD-1 codes.
KOEO readings were:
157 - (R,M) Mass Air Flow signal is/was low or grounded - MAF [Understandable, had the MAFS disconnected to get it started]
543 - (O) Fuel pump monitor circuit shows no power - Power / Fuel Pump Circuits

KOER readings were:
173 - (R,M) Oxygen sensor not switching - system is or was rich - Single, Right or Rear HO2S - Fuel control
(R) Oxygen sensor not switching/system rich Left or Front HO2S - Fuel control

Halp.

___

Hi guys,

First post (translation: I am suuuuuuper stumped.):

I've got a 1993 Ranger with 95k miles on her (thank god for retirees), and over the last month she's become harder and harder to keep running upon starting. The engine turns over OK and fires, but unless I'm riding the gas for the first ten seconds or so (and it's become worse over time, taking more and more to keep it running - at this stage I'm all the way to the floor and it'll still die on occasion), the engine slips into the 100s on the tach, burbles, and dies. If I can keep it going for more than about ten seconds, it idles just fine and is totally driveable.

So for attempted solutions I have:
-Cleaned the old IAC, and then replaced it outright
-Checked the intake for obstructions
-Blasted the MAFS with the appropriate cleaner
-Swapped in a new fuel filter

I have a coolant temp sensor that I'm going to put in as soon as I can find a 25mm crescent wrench (anyone in Seattle wanna let me borrow one? :D ), but I don't think that's it; disconnecting the MAFS entirely has it starting and running perfectly fine (although at that nice high idle). Thoughts? I'm down to bad MAFS or vacuum leak, but I'm honestly a little intimidated by the prospect of tracking that one down.

(Disclaimers: I don't think it's related, but I need to replace the valve cover gaskets; driver side cylinder closest to the firewall is leaking.)
 
Last edited:


enjr44

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02 2X4; 08 FX4
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Ford
Engine Size
4.0 SOHC
Transmission
Automatic
Clean and test the IAC? Pull it off and with connected turn the key to run, should open all the way.

Test the ETS (two wire), it tells the engine how rich it needs to run when cold. Sort of like an old fashion choke.
 

spirograph

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Manual
Update:

Whatever it is has finally crapped out on me :( motor will crank but not fire.

Autozone's fuel pump tester rental doesn't have the right size adapter for the fuel rail pressure port, so I'm going to pull the valve core and see if I can just hose clamp it to check for fuel pressure. Gotta get a friend to come help me check the spark (for ICM, wires, and coil pack), unfortunately. Thoughts on what else that might be?
 

enjr44

Active Member
U.S. Military - Veteran
Joined
Mar 24, 2013
Messages
1,142
Reaction score
9
Points
38
Age
78
Location
Renton, WA
Vehicle Year
02 2X4; 08 FX4
Make / Model
Ford
Engine Size
4.0 SOHC
Transmission
Automatic
Spray some starter fluid into the intake tube (at the air filter end). If it starts or tries to start, it is probably fuel related. If nothing, most likely spark. But, I am leaning toward fuel.

When the fuel pump finally died (almost died and then really died) on my 02 it would start and then die. If I got it above 1k it would stay running and once warm would restart without problem for about an hour. That is until it quit completely. When you turn the key from off to run the fuel pump runs for 2/3 seconds and then shuts down until engine is above 300 rpm. If there isn't enough fuel pressure to get it above that it will run out of fuel really quick because injectors need pressure to operate.

If the check valve in the pump is failing you may not have enough pressure to get it above 300 rpm to turn the pump back on. That is what mine was doing until it died completely. A good check valve will hold 50 psi for months.

First have someone turn key from off to run while you listen with your ear at the fuel filler pipe to see if the pump is turning on. If it is, you will hear it!! If it doesn't turn on come back and we can go through troubleshooting that.

If it does turn on, try this, turn key from off to run for a few seconds, back to off, repeat 3 or 4 times. On last cycle after the 3 seconds try to start it. The pump (a good/new one) can raise the pressure about 15 psi each cycle. If it starts the check valve maybe toast.

Go to Harbor Freight and buy a $30 fuel pressure tester and see what the pressure is really doing. My pump died right in front of my eyes. Then later, you can rent it to your buds for a couple of beers when they need it. High pressure pumps are not going away.

And, IMO, if it is a bad pump, get a good one. Delphi or Motorcraft comes to mind. Those cheap ones are known to last about a year (10 days past the guarantee).
 

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