Tried replacing my IAC, and my starting problems are now noticeably worse, which is... interesting. Now the car will stall out completely without throttle input upon startup. Any idea what this could mean?
Interesting, I didn't know about that. Guess it wouldn't be too hard to take a look, although my car is a 1993 so you would figure that Ford would have fixed issues like that by then.It can cause all kinds of weird problems.
I will try this as well.With the engine running, Unplug the IAC. Does the engine stall?
If so, the throttle blade is too far closed. Need to open the set screw a bit and perform an idle relearn procedure. Sometimes when the IAC is being called on to 100% manage idle due to the blade being closed too much) you get a surge on startup. The car should be able to idle somewhat (although at a low rpm) on it's own with the IAC unplugged.
The thing that is really throwing me for a loop is that the car behaves so well once it's done having it's little hissy fit upon start up. I feel like that would rule out something like a vacuum leak or fuel pressure problems. I will look anyway though. I also doubt that air flow to the MAF could be disturbed since it has a stock airbox and stock intake tubing.Vacuum leak
Low fuel pressure
air flow disturbed going through MAF
mis matched MAF/injectors
improper reset procedure
wrong/mismatched/worn parts
wiring issues
ignition switch
I have a factory A9L and factory tune, it even still has the little "do not remove or it will void your warranty" sticker over the opening.I'm not sure if this has been asked yet. I did a quick browse of the comments. Do you have a stock computer with a 4 bank chip?
Any corrosion on the MAF Connector pins? And maybe the IAC Connector since I saw you ran into an issue with that? If no corrosion is present, the terminal ends could just be spread from being removed numerous times (being 30 years old doesn’t help either, if the harness is stock)After further diagnosis I am pretty convinced that there is something wrong with the MAF circuit. I can unplug basically every sensor or combination of sensors and it doesn't change the starting condition except if I unplug the MAF, at which point the car starts and idles rough (as you would expect to happen when unplugging the MAF) but the engine is stable and does not surge. Since the MAF is new and I tested two different new sensors, I think I can conclude that the sensor itself is not the problem.
Now I am wondering if there are any common failure points in the MAF circuit that I should look for, such as the connector, somewhere a wire could become worn, or if the ECM could have issues. I will test all the wires but it's kind of a PITA so I was just hoping to be pointed in the right direction.