RPMs dropping and stalling at stoplights

[mr_manny]

Have you verified your fuel pressure?
You can hookup a fuel pressure tester at the fuel filter easy enough.

I'm running an adapter at the fuel rail, that lets me utilize a water filled mechanical gauge. Peace of mind that simply requires you to pop the hood to verify.

 

[keel]

Okay I've been driving the truck to work for a couple of days now after replacing the IAC and oxygen sensor + resetting the computer by disconnecting the battery and no more stalling or falling RPM issues, engine idles nice and smooth. I think ultimately it was the IAC that solved my problem.

Thanks for the help everyone.

The tachometer is still wildly inaccurate though so I'm still taking suggestions about that.

 

[PetroleumJunkie412]

Good to hear.

Hall effect controls tach IIRC, along with ecm and gage cluster.

Thwres a wiring diagram around here somewhere

@pjtoledo

 

[RangerNumber3]

Get some throttle body cleaner. Works wonders for rough idle and stalls when stopped.

 

[keel]

Hall effect controls tach IIRC, along with ecm and gage cluster.

If the hall effect sensor was bad wouldn't the engine also run poorly/not run at all though? Since it acts as a crank position sensor for the ECU.

 

[PetroleumJunkie412]

If the hall effect sensor was bad wouldn't the engine also run poorly/not run at all though? Since it acts as a crank position sensor for the ECU.

Theoretically, yes.

Obd1 is weird tho. Prone to electrical ghosts.

Need to look up tach signal diagram again...

 

[85_Ranger4x4]

And old gauges do old gauge things...

 

[Kenobi77]

Okay I've been driving the truck to work for a couple of days now after replacing the IAC and oxygen sensor + resetting the computer by disconnecting the battery and no more stalling or falling RPM issues, engine idles nice and smooth. I think ultimately it was the IAC that solved my problem.

Thanks for the help everyone.

The tachometer is still wildly inaccurate though so I'm still taking suggestions about that.

Try replacing your coil. I was chasing symptoms like yours a few weeks ago that ended up being my ECU. In the process, I swapped three coils to rule them out. One of them made the tach bounce all over the place.

 

[keel]

Try replacing your coil. I was chasing symptoms like yours a few weeks ago that ended up being my ECU. In the process, I swapped three coils to rule them out. One of them made the tach bounce all over the place.

Okay I think my Mustang uses the same coil pack so I will try swapping that on.