Engine RPM slowly drops @ idle! suggestions???

[snb778 5,000+ posts]

how much did your MAF cost?

I don't want to jump to conclusions though

I also noticed the RPM's weren't 100% consistent.. it would fluctuate maybe 25+rpm either direction at idle only though

 

[Walled_Taurus 10+ year member]

My first thought was that the alt is almost shot. And if you get a min when you find out PM me im curious to know what it ends up being. Live in learn you know but if i don't here what the actual problem ends up being I wont learn shit you know.

 

[WOT]

Obviously dont replace the MAF on a whim. Grab some sensor safe cleaner and give it a good cleaning, only takes a couple mins, reset the ecu by disconnecting the battery for a couple hours. And see what happens

I dont think electrical (alt/battery/running voltage) would cause this at all though

 

[whitedragon551 5,000+ posts]

Any carb cleaner or brake parts cleaner will work on the MAF. Just make sure it dries all the way before putting it in. My MAF for my car ran me $40 but thats because I get club and sponsor discounts.

 

[BoxdGM 10+ year member]

wouldn't I have problems getting my car to rev up if it was M.A.F.?
(still no respenses on the ford forum) SO THANKS!

just went to get some food... and i noticed that when i pushed any of the door control buttons, the dash lights flicker real quick, not completely off, just noticeable though... is that normal on older cars? didnt effect the drop in RPM though...

first thing im going to do tomorrow is test the batt voltage, test the ALT voltage, disconnect the - and see if the car stays on, THEN i'll know if its electrical or not for sure

i would try cleaning the battery terminals, take them off and clean the post and terminals good with a wire brush, if your lights flicker when you use any power switches or brake lights etc..

I wouldnt just unhook your battery while its running, on older cars it was ok but it can cause voltage spikes that can harm your cars electronics. i dont do it on my cars personally but to each his own. BTW you would disconnect the +, when you take away the ground it will shut off.

 

[SicAudio 5,000+ posts]

To reset the ecm you disconnect both cables and hold them together for 2-5 minutes to drain the memory caps in the computer, sounds like a vacumn leak, which if it did throw a code takes quite awhile usually. and it will usually be p0171 and / or 174 lean codes, next time it does it see if it dies on its own. if it does it very well could be the IAC (idle air control) valve. the IAC being dirty or going bad will cause that symptom as well, but the vehicle will still idle in limp mode.

make sure the air filter is clean and listen for a vacuumn leak, you should be able to hear it as a loud hiss or sometimes a huffing noise. an alt going bad will cause it as well so the voltage check is a very good idea whoever mentioned it.

if it was the maf the car will show a code within minutes. the computer bases everything fuel and ignition related of of it, so I doubt that is it. and they either work or they don't. but Fords are notorious for iac problems and filthy throttle body assemblies, that both can create this sympton as well.

keep us posted and PM me if you have any ?'s I have Snap-on shopkey software that can assist with weird crap and how to test components ect. It is horrendously expensive but it is what we used at my shop so....

 

[pickup1 5,000+ posts]

might be clogged fuel injectors.

 

[snb778 5,000+ posts]

To reset the ecm you disconnect both cables and hold them together for 2-5 minutes to drain the memory caps in the computer, sounds like a vacumn leak, which if it did throw a code takes quite awhile usually. and it will usually be p0171 and / or 174 lean codes, next time it does it see if it dies on its own. if it does it very well could be the IAC (idle air control) valve. the IAC being dirty or going bad will cause that symptom as well, but the vehicle will still idle in limp mode.make sure the air filter is clean and listen for a vacuumn leak, you should be able to hear it as a loud hiss or sometimes a huffing noise. an alt going bad will cause it as well so the voltage check is a very good idea whoever mentioned it.

if it was the maf the car will show a code within minutes. the computer bases everything fuel and ignition related of of it, so I doubt that is it. and they either work or they don't. but Fords are notorious for iac problems and filthy throttle body assemblies, that both can create this sympton as well.

keep us posted and PM me if you have any ?'s I have Snap-on shopkey software that can assist with weird crap and how to test components ect. It is horrendously expensive but it is what we used at my shop so....

it does sound like I have a mini-turbo in the car when I give it some gas

just went to the car again... resting voltage is 12.15, car on its 14.48!!

 

[snb778 5,000+ posts]

just brought the car to a Mech. had him hook up the computer.... no codes showing up.

he said he could hear what he thought was the car running a self-emissions test....?? what does that mean?

 

[whitedragon551 5,000+ posts]

14.48 volts isnt anything to worry about. Off cars usually are at 12.8v and on they rest at around 14.4v. Your idle voltage is fine.

 

[snb778 5,000+ posts]

i know.. im saying i was impressed with 14.48

 

[snb778 5,000+ posts]

i would try cleaning the battery terminals, take them off and clean the post and terminals good with a wire brush, if your lights flicker when you use any power switches or brake lights etc..
I wouldnt just unhook your battery while its running, on older cars it was ok but it can cause voltage spikes that can harm your cars electronics. i dont do it on my cars personally but to each his own. BTW you would disconnect the +, when you take away the ground it will shut off.

yea but to see if your alt is properly working, dont you disconnect the - terminal

?

 

[SicAudio 5,000+ posts]

never disconnect any terminal running or you can fry the computer

 

[SicAudio 5,000+ posts]

did you buy the car from a dealer? if you did even used, federal law requires that it has to run correctly for emissions reasons, take it back and make them fix it.

if it isnt running right it wont pass emissions it could be a plugged egr valve as well.

 

[snb778 5,000+ posts]

there is no proof though that it didnt happen AFTER i bought the car