I bought a 1994 ranger a couple months ago for driving back and forth to work. I knew it had an ignition problem when buying it, but one thing led to another and it ended up torn all the way down to bare block. It had recently been rebuilt, and I found numerous things wrong, to include the front crankshaft pulley being notched in an attempt to advance the timing. Anyhow I got this thing all put back together, and it runs great when at operating temp. When you first take out driving it will spit and sputter and is extremely low on power until it hits operating temp. I thought this might be a vacuum or intake leak so I performed a smoke test with no luck. I was also pointed towards the ect sensor by a friend but nothing changed when I put a new one in. I also verified the iacv was working and not stuck. Could this be the computer feeding bad fuel rates to the injectors while in open loop before switching to closed loop. I am not sure what to look at at this point besides the computer.

 

Welcome to the forum

There are two temp units on your engine
ECT(engine coolant temp) sensor, used only by the computer, always 2 wire
ECT SENDER, used only by the dash board gauge, can be 1 or 2 wire
These work differently, not interchangeable
Sensor will have cone shaped tip
Sender a cylinder shaped tip

If ECT Sensor is working, then when you Cold Start the engine Computer(PCM) will set Choke mode, part of Open loop.
All gasoline engines need to be "choked" when cold, fuel injection can't change that.

Since there are no "jets" to suck extra fuel from using a "Choke Plate" the PCM must do that, inject extra fuel to run Rich mix until engine warms up.

So Choke mode is high idle, at least 1,100rpms, Rich fuel mix, and advanced spark timing, same as choke plate did on carb engines.

So is your PCM setting Choke Mode?
Are you getting the 1,100+ rpms at cold start, then idle will slowly go down as coolant warms up?


Open Loop means O2 sensors are not hot enough to work, they need to be at/above 650degF to read the Oxygen levels in the exhaust accurately
During open loop PCM uses "tables" in memory for air/fuel mix, these numbers are modify by ECT and IAT(air temp), and these set Choke Mode
If a main sensor like MAF or O2 is disconnected or acting up, PCM will switch to Open Loop but if ECT shows warm engine then no Choke Mode

 

As far as the ect sensors I understand the difference, however both are new bc the sender was bad when I rebuilt the engine and I suspected the 2 wire computer sensor up front to be bad when I started having this problem. I went ahead and switched it out hoping to fix the problem. This brings me back to what I was originally asking I guess...with a known good coolant sensor (assuming the resistance tables I found when testing it are correct) would it more than likely mean I have a messed up computer...i.e. Its never going to open loop and just stays in closed loop from the time I start it? Or am I missing sth obvious

 

Well the high idle on cold start would indicate computer is in open loop, and ect is working

And dropping idle as coolant warms up would indicate computer is seeing higher coolant temp and recognizing it.

Computers do fail, but it is rare, very very last thing on the list.

If the check engine light is working, on with key and then off after engine starts.
Then you could do a sanity check by reading codes
On a 1994 you can do that using check engine light and counting flashes

You read it first then clear it by turning off key while its still flashing

Then unplug MAF sensor or TPS sensor and start engine, wait for CEL to come on because sensor is disconnected and then read codes again to make sure it ID correct problem.

But yes you can just replace computer on speculation, could be the problem

 

There is no high idle at a cold start and it does throw engine codes and will clear them out. As far as the high idle goes when cold tho it would be hard to tell because its sputtering so bad. It does not give me any engine codes while driving but I did unplug the maf sensor the other day to see if it was working and it threw a code and I cleared it successfully...I guess I just dont understand what other sensors to check...ive checked the iacv, maf, tps, and the engine sensor. At the same time idk how to verify the computer is at fault either?

 

Reads like computer is OK

If computer is not going into Choke Mode then engine would barely run until it warmed up a bit.
And you're back to ECT sensor, which sets Choke Mode.