So I have a 2001 ranger 4.0l. It’s been misfiring for a while but now that we’re getting into the colder months here it’s getting a lotttt worse. The colder the temperature the worse it gets. The only codes I’m getting are, running rich on bank 1&2, and insufficient coolant temp for closed loop fuel control. No misfiring codes. So far I have changed plugs, plug wires, new o2 sensors, new maf sensor, new thermostat housing and new 192 degree thermostat, new fuel pump and filter and it has an aftermarket intake but it was misfiring before the intake. I’m completely stumped on what this could be I feel like I’ve gone through most things that could cause this. Any help is appreciated thank you.

 

forgot to mention when it’s the worst. It idles fine and does ok if you’re super light on the throttle but as soon as you get over 1/4 throttle it just misses and bucks super bad.

 

Good to post the actual codes

Are these the only codes
P0172 System too Rich (Bank 1)
P0175 System too Rich (Bank 2)

For coolant temp what was the code?
P0115 Engine Coolant Temperature Circuit Malfunction
P0116 Engine Coolant Temperature Circuit Range/Performance Problem
P0117 Engine Coolant Temperature Circuit Low Input
P0118 Engine Coolant Temperature Circuit High Input
P0119 Engine Coolant Temperature Circuit Intermittent
or
P0125 Insufficient Coolant Temperature for Closed Loop Fuel Control
P0126 Insufficient Coolant Temperature for Stable Operation

Any P1XXX codes?


Rich codes are fairly rare compared to Lean codes
Rich and Lean codes don't mean the engine is actually running Rich or Lean, these code are set by the computer because its Fuel Injector OPEN TIMES are more than 15% off its original calculations, in the case of Rich codes it means computer is adding LESS gasoline than it calculated
If an engine is actually running Lean it will ping/knock
If an engine is actually running Rich you will have smoke out the tail pipe, and blacken spark plug tips, MPG in the toilet

When you changed spark plugs what did the tips of old spark plugs look like?

Could be you have clogged exhaust, idles OK but misfires as RPMs(outflow) increase quickly
You can test for that with Vacuum gauge, $10 tool, great for engine diagnostics

 

Yes those were the only codes and the other one was a p0125. I’m just stumped about why the colder the outside temperature is, the worst it runs and so far everything I have done has not been helping. The spark plugs didn’t look too hateful, a brownish tan color. When I put the new plugs in it seemed to help a little bit for a couple weeks then it started to get bad again.

 

Fan clutch locked up ?

 

could possibly be I’ll check that. One thing I forgot to mention was that I did hook a live data scanner up to it, and the hottest the engine got to was 170 degrees. That was just letting it idle as soon as you start driving it cools down to about 155-160. Not sure if it’s an accurate reading or If it’s just not getging up to temp. It has a brand new 192 degree thermostat in it. so maybe ect sensor is bad?

 

What does the dash temp gauge show?
They use two different temp sensing devices, 5 volt ECT sensor for computer
And 12 volt Temp Sender for dash gauge

Just under 1/2 on gauge is about 190degF, normal operating temp, 1/2 way on gauge is 205deg

 

Temp is reading just under half on the gauge and it stays consistent on the gauge the whole time.

 

Yes, replace ECT sensor

 

Did replacing the ECT sensor resolve the issue?