Engine Surging idle only on start up
- Thread starter keel
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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.
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.
I will try this as well.
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.
I at least know that the MAF and injectors and any other electronic sensors are correct parts because it is all OEM equipment (or an OEM equivalent replacement).
Could it be O2 sensors? I will say that I have Bosch O2 sensors and they have always been a little problematic and I have been considering switching to Motorcraft ones. My impression on how they work though is that the computer doesn't take inputs from them until reaching operating temp so I don't know how they would affect the engine start.
I want to say the Motorcraft units are just reboxed Bosch. I have run Bosch units for years and zero issues. If you are not getting a rich or lean code pointing to the O2's then I would say they are fine.
I replaced the switch in my 93 years ago as it fell apart but I caught it and was able to run two zip ties until I got a new switch and was able to install it over a weekend. This was back when I was driving the car everyday.
I replaced the switch in my 93 years ago as it fell apart but I caught it and was able to run two zip ties until I got a new switch and was able to install it over a weekend. This was back when I was driving the car everyday.
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.
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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.
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.
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