Mustang dies at Highway speeds!!

[kylebgt]

This is really getting on my nerves because of how dangerous it is. Basically, my car will try to kill itself when I push the clutch in and roll to a stop in neutral. I have seen sooo many people complaining about this and all everyone says is "its the IAC" well I replaced that and it is still doing it This CANNOT be good for the engine. When I am coming to a stop the revs will drop and hold at 1k like normal, then down to 700< ok little low but still ok then it will nose dive to 500 and all the way down to 100 at this point the power steering basically shuts off and half the time the engine stalls. If I do come to a stop without it dying the revs will bounce between 100-500 continuesly for about 10 seconds and then eventually find its way back up to 750. What could this be!!!! fuel filter, spark plug wires, mafs???? it is complete and if my car keeps on doing I might be forced to sell it

 

[the98stang]

Did you replace it with a motorcraft IAC? Did you reset the PCM? If yes, trying cleaning the MAF.

 

[03ghoststang]

my car did something similar when it was new ended up being a connector by the battery junction box

 

[fast97gt]

did you disconnect the battery for a few mins. if you didnt do it, and always do it after and during installing new parts. but i would check the connections on the maf sensor, and clean it with carb cleaner

 

[BennyBlown2v]

did you disconnect the battery for a few mins. if you didnt do it, and always do it after and during installing new parts. but i would check the connections on the maf sensor, and clean it with carb cleaner

They make MAF cleaner, carb cleaner can eat away at the some of the coatings and plastics used in maf sensor assemblies.

I have this same problem with my car...I replaced the IAC with a new ford one, messed with everything I possibly could think of...and still not fixed. My guess is its an IAC tuning issue, one which it seems like a lot of people (modularpowerhouse included...) have trouble tuning out.

 

[the98stang]

could be IAC/dashpot tuning issue as well

 

[kylebgt]

Yeah I have disconnected the battery numerous times. Defiantly not a problem with the ECU. I am starting to the that whoever programmed the Engine Control Unit for Ford did a ****ty job and the computer isnt telling the IAC how to function properly. I have searched and searched but cannot find an answer. I think that I may change the fuel filter next, hopefully thats what it is

 

[[BlackDiamond]]

I hear a lot about this problem but never had it... why would some people have it and some never?

 

[jstreet0204]

There are many things that effect idle problems like this, that is why they are hard to troubleshoot. Fuel trims, IAC, TPS, Battery voltage, vacuum leaks, fuel filter, etc. Datalogging the issue will greatly improve your chances of fixing the problem without throwing parts at it. So if you don't have the ability to do it yourself, you may want to take it to a shop.

On another note, when it happens while rolling, and you lose power steering, just let out on the clutch to start it back up.

 

[fast97gt]

They make MAF cleaner, carb cleaner can eat away at the some of the coatings and plastics used in maf sensor assemblies.

I have this same problem with my car...I replaced the IAC with a new ford one, messed with everything I possibly could think of...and still not fixed. My guess is its an IAC tuning issue, one which it seems like a lot of people (modularpowerhouse included...) have trouble tuning out.

i did not know this about the maf cleaner made specifficly for this application think you for correcting me, by the wayive not had this problem yet

 

[hotmustang331]

They make MAF cleaner, carb cleaner can eat away at the some of the coatings and plastics used in maf sensor assemblies.

I have this same problem with my car...I replaced the IAC with a new ford one, messed with everything I possibly could think of...and still not fixed. My guess is its an IAC tuning issue, one which it seems like a lot of people (modularpowerhouse included...) have trouble tuning out.

That shouldnt be hard to take car of. Like 98stang said, it looks like a dashpot tuning issue. Raising the idle RPM for dashpot mode (or inotherwords, while "moving" over XX set MPH) SHOULD take care of this issue. Ill take a look to see exactly what can be done...I havnt opened the PR software in about 3 weeks

 

[cooper]

my car did this too. iac , and optima batery change helped some. Do NOT try to clean the MAF or IAC with spray cleaner this will f it up. Im not sure of a fix ,cause my car still some times stoping at a light the rpm's will drop to 400, untill a compleat stop and will regain normal 800-875 idle, but it dosent die .

 

[Chris00GT]

I've seem this problem sometimes being caused by cold air kits. I'd remove it and re-install the stock setup and see if it helps.