Engine Trouble

RonneyJAyala · Dec 6, 2015

Sooooo have I got something to say. This weekend was my Fiancé and my 3rd anniversary. We decided to go play up in the snow in my 92 Ranger v6 4.0 efi. Well truck is doing fine till we start heading back up the trail we were on

Just for a reference on how rough the trail was. In total we heading back and I start going up the hill, mind you I'm in 4 low, 2nd gear cruising, so I'm going up this hill 2nd to 3rd fine get near the top start pulling 2,600 RPMs doing fine, hit 3k and bam it starts sputtering away at me. My truck will not go past 3k RPMs now? Even in gear or in neutral. It just sputters and the tac gauge goes crazy. My question is, what the hell is wrong? Going up to this spot it was sort of doing the same thing, going up hills it would sputter pulling higher the 3 grand. I'm a decent DIY kind of guy, but I can't figure this out, and I need help haha. Anything would be greatly appreciated!

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RonD · Dec 7, 2015

Could be running out of fuel pressure, higher RPMs = higher demand of fuel
How old is fuel filter?
'92 should have 35-40psi pressure at the fuel rail, if you put a gauge on it run RPMs up to 2,500 and hold it there, see if pressure is starting to drop.
At idle remove vacuum line on fuel pressure regulator, pressure should go up to 40-45psi and hold there.

Could be TPS(throttle position sensor), this is like a light dimmer or volume control, a variable resistor, so can get "dead spots".
It has 3 wires
Top wire has 5volts from computer
Center wire sends voltage back to computer
Lower wire is Ground.

Key on engine off, with throttle closed
Center wire should have under 1volt, .7-.9volts is spec
As you manually open throttle, voltage should increase steadily no jumping around
When you get to wide open throttle voltage should be above 4.5volts.

TPS is the only sensor the computer has for driver input on how fast you want to go, lol.
If it is only going up to 3volts, for example, computer is feeding limited amount of fuel into engine for that voltage, throttle plate is open more but computer doesn't know that, so fuel mix is lean.
I would expect CEL(check engine light) to come on because of this, MAF(air flow) sensor and TPS are compared and computer should set a code that they don't match.
Does your CEL come on with the key and then go off after starting engine?

I don't think 1992 computer had a REV Limiter, it could have, 1995 and up next generation computers have that.
REV limiters would cut in around 3,000rpm, but only if clutch pedal was in, auto was in Park/Neutral and speedo was below 5MPH

adsm08 · Dec 7, 2015

I'd suspect the fuel pump as well. That's about the speed I'd expect it to start having issues keeping up.

A 92 should not have a rev limiter.

RonneyJAyala · Dec 7, 2015

My CEL comes on when the key is on and goes away when the truck is started. I don't recall when my fuel filter was last replaced due to I just got the truck a year a go from a family member who took great care of the rig. I'll call them tonight and ask, but the fuel pressure is what I was thinking as well. Another possibility from the guys I work with is my truck is in a "Safe"/"Limp" mode? Any word on that?

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RonD · Dec 7, 2015

Open Loop is what the truck starts off in every day when coolant is cold, and no that won't effect maximum RPM.

After warm up of coolant, and O2 sensors, computer goes into Closed Loop.

If a main sensors fails outright computer will go back to Open Loop, which is what some people call Limp Mode.
Computer has parameters in memory for all the sensors, if a sensor is consistently sending data back that is outside the parameters in memory then computer will assume it has failed and relay on factory settings at that point, Open Loop.

Open Loop is when computer is running the engine based on factory pre-set mix and operation numbers, performance is basic, MPG is not as good as Closed Loop.

People might associate a failed part and it has causes engine to run poorly with Limp Mode designation, i.e. the engine is running like sh!t so computer must be in Limp Mode, lol, engine is in Limp Mode yes computer is in Open Loop most likely.

Limp mode can also refer to automatic transmissions that are computer controlled.
If transmission feed back isn't within parameters computer may switch to basic shift points ignoring other sensors, so you can Limp Home.

But if Open Loop or Limp Mode happens when engine coolant is warmed up, computer will set a code and turn on the CEL.
If CEL is Flashing that means "Danger Will Robinson", usually a misfire that is detected by Crank Sensor(CKP), or feedback on coil pack, or extreme Lean condition that can't be compensated for.
CKP measures the power added each time a cylinder fires, by counting pulses and the time between them, power added means time is less, if misfires are adding time between pulses this could damage engine so CEL will Flash.
Feed back on Coil means possible spark plug melting causing damage, Lean condition can cause total melt down of pistons.

I thought some of the 4.0l and 3.0l with Cam Position Sensors(CPS) would act up pretty bad when this sensor failed, I chalked that up to good planning on the programmers part since CPS drive is also oil pump drive, so lack of CPS signal could mean NO OIL PUMP, destroyed engine mode

RonneyJAyala · Dec 7, 2015

RonD said:
Open Loop is what the truck starts off in every day when coolant is cold, and no that won't effect maximum RPM.

After warm up of coolant, and O2 sensors, computer goes into Closed Loop.

If a main sensors fails outright computer will go back to Open Loop, which is what some people call Limp Mode.
Computer has parameters in memory for all the sensors, if a sensor is consistently sending data back that is outside the parameters in memory then computer will assume it has failed and relay on factory settings at that point, Open Loop.

Open Loop is when computer is running the engine based on factory pre-set mix and operation numbers, performance is basic, MPG is not as good as Closed Loop.

People might associate a failed part and it has causes engine to run poorly with Limp Mode designation, i.e. the engine is running like sh!t so computer must be in Limp Mode, lol, engine is in Limp Mode yes computer is in Open Loop most likely.

Limp mode can also refer to automatic transmissions that are computer controlled.
If transmission feed back isn't within parameters computer may switch to basic shift points ignoring other sensors, so you can Limp Home.

But if Open Loop or Limp Mode happens when engine coolant is warmed up, computer will set a code and turn on the CEL.
If CEL is Flashing that means "Danger Will Robinson", usually a misfire that is detected by Crank Sensor(CKP), or feedback on coil pack, or extreme Lean condition that can't be compensated for.
CKP measures the power added each time a cylinder fires, by counting pulses and the time between them, power added means time is less, if misfires are adding time between pulses this could damage engine so CEL will Flash.
Feed back on Coil means possible spark plug melting causing damage, Lean condition can cause total melt down of pistons.

I thought some of the 4.0l and 3.0l with Cam Position Sensors(CPS) would act up pretty bad when this sensor failed, I chalked that up to good planning on the programmers part since CPS drive is also oil pump drive, so lack of CPS signal could mean NO OIL PUMP, destroyed engine mode

What does this mean for me? My truck isn't sending a check engine code. The only time it'll throw a code is if I make the truck hit above 3k RPMs (down shifting to second going 45mph) But it goes away after it drops back down?

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cp2295 · Dec 8, 2015

That's it saying its misfiring, or as Ron stayed too lean. Could be because fuel pressure isn't high enough (or fuel injector, regulator, or rail is clogged) and causing a lean condition above 3k. If fuel pressure is low replace the pump, strainer and filter. If that doesn't fix it only other thing it could be is the regulator but you can check that by pulling the vacuum line and smelling/looking for an obvious gas leak inside the regulator. (Vacuum line will be wet with fuel).

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RonneyJAyala · Dec 8, 2015

Would that cause a rev limiter type scenario? I'll try to get a video of it doing it

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RonneyJAyala · Dec 8, 2015

Also, where would said vacuum be?

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cp2295 · Dec 8, 2015

It cutting out because There's not enough fuel, regulator is on the fuel rail, vacuum line is on the regylator

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RonneyJAyala · Dec 8, 2015

A guy at my work, which is a mechanic shop just rode with me and he says that's it sounds like my computer is cutting the fuel.

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RonD · Dec 8, 2015

Find your OBD1 connector, it should be in the engine compartment between power booster and fender, some times under battery.

Look here: http://www.therangerstation.com/tech_library/OBD_I.shtml
2nd drawing down is what it looks like.
And Fuel Pump is labelled on that drawing.

With Key ON
Use a short wire and Ground the Fuel Pump slot in that OBD-1 connector.
Fuel pump should come on.

This ground is the same wire computer uses to operate the Fuel Pump relay.
You can leave it connected and go for a drive, see if problem reoccurs.
If it does then could be fuel pump relay or fuel pump itself, but it won't be computer, it is out of the loop with that jumper in place

RonneyJAyala · Dec 8, 2015

Okay here's what happened, I've been asking the guys at my work and stuff and I finally got it to go into the shop. One of the main guys there looked at it off and running and finally concluded that I have a major intake leak on the lower intake gasket. Could that be the problem? He said my motor is running very rich due to this, he also did a fuel pressure test. But since the air is comming in through s leak the computer is trying to compensate by throwing my fuel into the system. So, if I floor it, and the computer reads that it's throwing to much fuel could the computer then stop the fuel at a certain rpm?

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cp2295 · Dec 8, 2015

Yeah definitely fix that before attempting other fixes.

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RonneyJAyala · Dec 8, 2015

Planned on it! Already got the parts on order, gotta pick em' up tomorrow, then fix it on the weekend. Need to have as much time as possible to do it, shouldn't be to hard but from the computer it says it should take about 5 hours for a person who knows how, or has done it. I know how but never have I done it.

I will update you guys if this fixed the problem. If it doesn't, back to square one!

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