New to the group! Working on a 91 3.0 v6 ranger. While idling its smooth and does great, but once driving it pulls good for a few seconds and then its starts to sputter and cut out real bad. I don't have throttle response during that, but I can pat the throttle and evenutally clear out for a few seconds. Any ideas of the problem?

 

Welcome to the forum

With symptoms provided, it reads like either a clogged fuel filter or failing fuel pump

Could also be partially blocked exhaust(collapsed Cat or muffler), similar symptoms

If you can test fuel pressure that could tell you if its a fuel flow issue, 1991 expected running pressure is 30-35psi, raise RPMs to about 2,000 and hold if pressure starts to drop then its a fuel flow issue

Use vacuum gauge to test exhaust, should see 17"-20" of vacuum at idle, raise RPM just a bit and hold, if vacuum starts to drop after holding then clogged exhaust

 

Well the kid i got it from straight piped it which I hate and going to fix. And the fuel pressure is a 33psi during idle and at steady 2000rpm its reading 30psi.

 

With a matter of 30 seconds of pulling out the driveway it starts and comes to a point to where it dont want to go anywhere. Once stopped you can pat the throttle and there's no response. Its like it burns all the fuel out the rail and then once it fills back up it will do fine for the next 30 seconds

 

With a matter of 30 seconds of pulling out the driveway it starts and comes to a point to where it dont want to go anywhere. Once stopped you can pat the throttle and there's no response. Its like it burns all the fuel out the rail and then once it fills back up it will do fine for the next 30 seconds. I'm also looking for a cluster layout so I can tell what lights are on..

 

That would show up on fuel pressure test, so not a fuel issue

And with fuel injection you need to think a little differently, there is no "gas" pedal, its an air pedal, so when you 'feather' the "gas" pedal you are adding more air not more fuel
Fuel injection doesn't have an accelerator pump like a carb did, which did pump extra gas in when you pressed the gas pedal

There is a TPS(throttle position sensor), which "kind of" does the same job, it gives the computer a "heads up" that driver wants to accelerate
An issue with the TPS would set a code, and CEL(check engine light) would be on, which you don't mention

So what you are saying is that it ONLY does it under Load?
So you can REV engine as much as you want in the driveway but once engine needs to pull a load(vehicle) is when it stumbles?
Manual or automatic trans?

 

Its manual trans and I do have a light that comes on evenutally but not sure if its the CEL because the cluster labels have been taken out. When its just sitting and at idle I can give it all the pedal I want and it does fine, just when its under a load.

 

What do your spark plugs look like ?

Many years ago I had a van that behaved exactly like that, $500 in parts later and still not getting any better, I checked the plugs, I should have checked them first, I would have saved a lot of money and time.

 

The cap,button, plugs and wires are new as of yesterday.

 

OK, then

CEL should come on with key on, far left bulb in 1994, not sure on '91, amber color
But it will go OFF when cranking engine over
Once engine starts if there are codes in memory it will come back on again

In 1991 you should be able to read codes by counting flashing CEL with jumper wire in place in engine bay OBD1 connector

Instructions here: https://www.therangerstation.com/tec...ry/OBD_I.shtml

CEL is also called MIL(malfunction indicator lamp)
You don't need the volt meter

Key off, install jumper as shown
In cab have pencil and paper ready
Turn on the key, engine off

1991 3.0l should use 3 digit codes
A 1 1 1 code means system is OK but wait to see if there are an memory codes

If 1 1 1 repeats then no codes

If you pull out the jumper wire with key still on it will clear all codes if there were any
If you turn off the key and pull jumper it will retain the codes

 

Just put a tps sensor on and made no difference. No CEL either. Will the enertia switch show signs or will it just go bad?

 

Inertia switch is an on/off switch and can't reset itself, so no can't cause an issue like you describe

 

Didn't think so. Could the computer possibly be bad?

 

Sure, almost 30 years old

Pull it out and open it up
There are 3 capacitors that can leak and cause fuel pump and running issues
Just had to change the 3 in my 1994, costs less than $5

There is no "must be computer" issues, but if you have tried pretty much everything else.........................then why not have a look

 

Was able to check the codes and what im getting is code 15, 41, and 95.. all related to fuel. Where should I start?

 

You should post the code definitions as well, first because no one has them ALL memorized, lol, and second so we can see that you are using the correct definitions

Ford 2 digit list here: https://www.therangerstation.com/tec...gitcodes.shtml

15 No Keep Alive Memory power to PCM pin 1
41 System lean - Fuel control
95 Fuel pump: open, bad ground or always on - Power / Fuel Pump Circuits

15 just means you have unhook a battery cable at some point in the past few weeks, or you have a bad battery cable

41 means the computer is having to open the fuel injectors longer than it calculated to get O2 sensor in the correct range
Engine is not actually running Lean
This code can also be from misfires in the engine, rough running

95 is the concern at this time, and it can cause the code 41 as well
The computers pin 8 is spliced to the Fuel Pumps 12volt wire, when key is turned on the fuel pump should run for 2 seconds and then turn off, when its off pin 8 should show a GROUND coming from/thru the Fuel Pumps motor, and its not, so code 95
So at some point the fuel pump is turning off because of the lack of a good ground, or fuel pump itself is failing

So I think you will need to lift/move the bed and get at the fuel pump wiring, there are 4 wires at the tank
pink/black and black are fuel pump, pink is the 12v wire and Black is the ground
Yellow/white and black/yellow is for fuel level sender(float) yellow goes to gauge, black/yellow is ground

The black and black/yellow are spliced together and then grounded
You will need to test the black wire for a good ground or run a new ground from frame and splice it to that black wire to make sure its a good ground full time

Also test the tank wires to the pump with OHM meter, should see under 10 ohms, if higher pump motor is failing

 

How many O2 sensors and cats should it have? Who I purchased from has it straight piped with no O2 sensors or cats. Will this cause the lean code?

 

1991 3.0l Ranger would have/need two O2 sensors, one near each exhaust manifold, so one on each side of the engine

There was no downstream O2 used on Rangers until 1995 and up, so not having Cats wouldn't effect computer or set codes, just illegal, lol, federal illegal

Not having BOTH Upstream O2 sensors would set codes, 41 and maybe 43

EDIT:
1991 3.0l may only have 1 O2 sensor just after "Y" exhaust pipe comes together, so it gets/"sees" exhaust from both sides of engine
Same codes apply

 

Does anyone have a diagram or a picture of the gauge cluster on a 91 3.0 xlt? Mine has the bulbs but not the picture to identify the light.

 

Don't have an owners manual for a 1991 Ranger and didn't see a downloadable one

There are some for sale on ebay, or check local wrecking yards they will sometimes save owners manuals in a pile

But a member here may have a 1991 and can get what you need

 

Thanks ill look into that.