1990 ford ranger 2.9 sputtering

[pbc243]

Hello, I am new to these forums and in need of some guidance.

I have a 1990 ford ranger with a 2.9l It seems as if once I start driving the truck for a few min til it gets about normal temp it starts to do this "surge" in the rpms. It idles fine far as i can tell at aprox 800rpm. I have replaced the following: all new plugs and wires, new coil pack, new distributor and verified correct firing order, TPS sensor (also adjusted), IAT sensor, new throttle sensor and also a new throttle.

Im kind of lost now, ive been replacing and replacing and everything that ive done has helped performance of the motor for sure but hasnt fixed my main issue of the sputtering.

I made a short video, but you can kinda see what im talking about with the RPMs spiking
https://youtu.be/ZbOM5InNgyQ

 

[adsm08]

Check the oxygen sensor. Just inspect it visually for damaged. It is probably your issue, but sometimes you can be sure of that by finding physical damage.

 

[RonD]

Welcome to TRS

1990 2.9l Rangers used MAP based computer system
MAP is Manifold Absolute Pressure
The computer us what sets the 14.7:1 air:fuel ratio and it does that based on RPM, Throttle position, and MAP pressure.
Computer is programmed for a 2.9 Liter engine, so it "knows" approximately how much air it will be sucking in at any given RPM, i.e. 2.9 Liters at Wide Open Throttle.
The MAP sensor tells it the Vacuum Pressure inside the intake, i..e under load or no load, so it can fine tune the air:fuel mix for best operation.

Check MAP sensors wire connector and its 1 vacuum hose to the intake
MAP sensor is often located on the upper firewall passenger side middle, small black box.

MAP sensors rarely fail, but vacuum hoses and connectors do

 

[pbc243]

Will check both of those out. I did notice awhile ago the air hose has been melted shut going to the MAP sensor which has been replaced. but I will go back outside and piddle around with it and hopefully bring back some good news.

 

[pbc243]

checked everything, far as i can tell map sensor looks good and o2 sensor looks fine. cleaned their connections. no changes. still having issues.

 

[IIBRONCOS]

Have you replaced the ECT (engine coolant temperature) sensor ?

 

[pbc243]

Have you replaced the ECT (engine coolant temperature) sensor ?

So I went outside and just realized that I made a complete idiotic mistake. I put my IAT sensor where the ECT goes and vice versa... Do you think that the IAT sensor will still work or would the antifreeze short it out?