What sensor is it

BRONCONUT · May 26, 2014

I just finished bolting up new heads on my 4.0 along with new plugs and wires. I also replaced the fuel filter here a few days ago.

When starting it stumbles around for about 10 seconds then idles up and runs smooth. If I put it under load by putting it in gear it stumbles. If I let it idle for a bit it will go in gear fine and drive but if you push the skinny pedal a little to much it stumbles.

I am leaning towards a sensor like o2 or maybe even engine temp. The engine temp sensor likes to peg out but I know its not running hot right after start up. It doesn't stay there either it will come down into normal ranges sometimes.

kimcrwbr1 · May 26, 2014

Sounds like you have a vacuum leak somewhere pull the codes and see if it points you in a direction. A good way to look for vacuum leaks is with a length of vacuum hose. Put one end in your ear and search around all the gaskets and fittings with the other the closer you get the louder the hissing will be. Did you put a new throttle body gasket on when you put it back together?

RonD · May 26, 2014

Computer can't use the O2 sensors until engine warms up a bit, O2 sensors don't work until they are 600degF or higher, so computer ignores them for a few minutes after start up, warm start a minute or so, cold start 5 to 8minutes.

The dash board temp gauge uses a 1 wire SENDER to get coolant temp.
The computer uses a 2 wire SENSOR to get coolant temp, they look similar and are often located near each other, but are not shared.

Cold start on EFI engine should see the idle going up to 1,400rpm then drop to about 1,000, then as engine warms up idle will drop down slowly until it is at 750-800 warm, 650-700 for manual trans.
If idle doesn't do this then could be Temp sensor or IAC valve issue, both can be test.

The computer uses the IAC valve to control the idle, but letting more or less air into intake.
Computer used the CKP(crank position) sensor to get the RPM
Computer uses the ECT "sensor" to get the coolant temp.

After engine warms up, 5 to 8 minutes, it should be idling about 750, unplug the IAC Valve connector, idle should drop to 500 or lower and engine may stall, either is OK.
If idle doesn't drop then you have a vacuum leak.

Vacuum leak causes lean fuel mix, when you open the throttle, adding more air, engine will stumble until mix richens.

Make sure MAF sensor is connected.

BRONCONUT · May 26, 2014

I put on all new gaskets and torqued everything to specs. I also checked for vacuum leaks by spraying ether around the engine compartment and the idle did not change. This is why I am leaning towards a sensor. I am open to try what ever though. I may pull it up in the shop again tomorrow.

1994fordranger · Jun 5, 2014

Mine had that exact problem and it was o2 sensors and idle air control motor

BRONCONUT · Jun 5, 2014

I have replaced the fuel pump and the thermostat today.(for different reasons) I pulled the tank and the pump I had installed a year or so back had all the rubber hoses and little rubber basket thing deteriorated to mush and bits and pieces in the bottom of the tank.

After getting it all buttoned up It started and ran fine for a good 5-10 minutes before I noticed that the temp gage was climbing a little high so I shut it down and felt the upper hose which was under some pressure and was hot enough that the t-stat should have opened. After I replaced it I now have a no start issue again. If I give it a little squirt of throttle body cleaner it will start and run. That tells me its not getting fuel. I took an air line and blew through all the fuel lines after disconnecting them all. What else should I try before pointing at the injectors? is there a good way for me to clean them?

RonD · Jun 5, 2014

Fuel pump will have a check valve which prevents you "blowing it out", and you would need to open the Fuel pressure regulator valve(apply a vacuum to it) to blow that line(and return line) out.

I assume you can hear the new fuel pump start for 2 seconds when key is turned on?

If so, I would check fuel pressure, could be blocked from debris that go in before you cleaned it out.

And then yes you would need to pull the fuel rails and check them and the injectors for debris

BRONCONUT · Jun 5, 2014

I will get back after it tomorrow, I had to walk away from it today. I am going to take the whole fuel system back apart and go from one end to the other. I will check the fuel rail for pressure before doing all the above.

BRONCONUT · Jun 10, 2014

Still not starting. I am about at the end of my rope with this truck. Fuel lines are clear, pump comes on but the gauge I hooked up and wont show pressure. The o ring in it that goes to the shrader valve is coming apart.

BRONCONUT · Jun 10, 2014

still acts like its not getting fuel. After priming the system it still has no pressure wont start it acts like its not getting fuel. I did check and it is getting spark.

BRONCONUT · Jun 14, 2014

A $1.47 piece of hose on the top of the fuel pump with a tear in it caused all the problems. I dropped the tank thinking the pump wasn't working good enough and when I removed it I found a tear in the hose that I did not replace. My pump did not come with it so I just reused the old. I put a new hose on and it runs great.

RonD · Jun 15, 2014

Good work

Thanks for the update and fix

BRONCONUT · Nov 28, 2014

Just to add to this thread on what was wrong, I had left something unplugged. As far as my fuel issue I replaced the fuel pump and the hoses in the tank. The hose I had got with the pump had gotten soft and came apart, I then put on another I bought from autozone that was supposed to be for gas but not for being submerged in it so it basically tore open and was dumping the fuel back in to the tank. Its hard to get the right fuel pressure at the rail with all of these problems. The ranger is now running great.

BTW this happened twice in a few months period.

RonD · Nov 28, 2014

Good work

Thanks for the update

What sensor is it

New Member

Well-Known Member

Official TRS AI

New Member

New Member

New Member

Official TRS AI

New Member

New Member

New Member

New Member

Official TRS AI

New Member

Official TRS AI

Sponsored Ad

Sponsored Ad

Member & Vendor Upgrades

Truck of The Month

Recently Featured

Follow TRS On Instagram

TRS Events

25th Anniversary Sponsors

Check Out The TRS Store

Sponsored Ad

Sponsored Ad

Sponsored Ad

Amazon Deals