RPMs Fall During Start-Up

[Art Garcia]

Last night when I got off work. I went to start my truck up and as always usually have to try about two to three times to get it running. This issue I believe is related the the infamous fuel pump problem. Usually if I leave it in the on position for ten seconds it will start right up.



Anyway It started the third time but the RPM fluctuated rapidly from 7500-200 and then it stalled. Could this issue be related to a bad PVC valve?



I have an aftermarket K N Cone filter

 

[Todd Z]

Did the engine actually rev to 7,500 RPM ??? or do you mean 750 ?....



CLEAN or replace IAC motor......Clean MAF and Clean TB



Todd Z

 

[Joe Godbee 2]

Sounds like a bad IAC to me.



Same thing happened to my last 3 Ford trucks. F-150, Ranger and Sport Trac.



I thought for sure it was a clogged filter or bad fuel pump, but after searching found that the IAC was most likely the culprit. Easy fix!



Best of luck.

 

[Richard L]

I agree with Todd Z. It sounds like your IAC needs to be cleaned or replaced. You still may have a bad fuel pump if it truck does not start unless you leave the ignition on for about 10 seconds for it to build up pressure...but once it starts the idle is controlled by the IAC...and I assume you mean 750 RPM and not 7500 RPM.



The oil used on the K&N filters is known to occassionally coat the MAF sensor wires and cause erratic running, but generally not a starting issue. The K&N oil seems to be more of an issue when the filter is over-oiled after cleaning...and that tends to be because of over-cleaning. The filter only needs to be cleaned and re-oiled every 50K miles. Any more often and you are wasting your money, damaging the filter....and perhaps oiling your MAF sensor which is not good.



...Rich

 

[Art Garcia]

I meant 750-2000. Our trucks RPMs only register to 6000.

I know I cleaned my cone filter at 25k. It was my first time doing so and I know for a fact that I over sprayed it with the oil.



I will follow the project on how to do that stuff. I also have to replace my whole thermostat housing, thermostat, and sensors. It started to leak again. Just gonna wait til a mild warm day.