Idle drops off to stall

[F23A1AT]

I need some help guys, I can't figure out whats going on. This has been happening to me for a while off and on but tonight it really had me worried. The engines revs drop off so far the engine will stall or come way to close to doing so <250rpm. There is no CEL and the issue is random. Sometimes it happens within 30secs of starting the engine and sometimes it can be as late as 20 mins later. This only happens between shifts if I take too long or when I'm approaching a stop light/sign and drop the clutch pedal to coast.


BTW the maintenance is completely up to date. Plugs 4k ago, oil yesterday, air filter cleaned a few weeks ago.


I am absolutely lost as to what this is. Please help.

 

[001Stunna]

Not sure if this would apply to you but on my car i had a similar issue...even though im Auto. When coming to a stop, and after fulling stopping in traffic the cars idle would go pretty damn low to the point where itd start shaking. The same would happen in neutral sometimes when switching from R-D or D-R. After cleaning the IACV, TB, TPS, MAP sensor the issue went away.

Other things it could be is possibly a weak alternator, but id say check TPS/MAP sensor voltages first.

 

[BadgerType]

what kind of acc are on? a/c? subs?

 

[F23A1AT]

Not sure if this would apply to you but on my car i had a similar issue...even though im Auto. When coming to a stop, and after fulling stopping in traffic the cars idle would go pretty damn low to the point where itd start shaking. The same would happen in neutral sometimes when switching from R-D or D-R. After cleaning the IACV, TB, TPS, MAP sensor the issue went away.

Other things it could be is possibly a weak alternator, but id say check TPS/MAP sensor voltages first.

I've been wanting to get another upper intake with all sensors for a while now I think maybe something is going bad. This one has an unknown number of miles on it but its probably in excess of 200k.

what kind of acc are on? a/c? subs?

Do you mean things that are turned on? I thought it may have had something to do with power consumption I turned the lights/a/c/radio off and the anomaly continued.

 

[001Stunna]

I've been wanting to get another upper intake with all sensors for a while now I think maybe something is going bad. This one has an unknown number of miles on it but its probably in excess of 200k.



Do you mean things that are turned on? I thought it may have had something to do with power consumption I turned the lights/a/c/radio off and the anomaly continued.

Just clean the throttle body, TPS, MAP, IACV and see if it makes a difference. Your only cost to you will be a can of electrical contact cleaner, can of TB cleaner and possibly some gaskets.

Also, test to see the voltage your battery shows on idle? at idle with accesories on(highbeams, stereo, a/c)? at 3000rpm? at 3000rpm with accessories on?
...simply to get an idea if your alternator is actually doing its work or not?

Edit: after cleaning the MAP/TPS...allow them to air dry(not using compressed air) and try not to touch the contacts too much.

 

[acedomain]

I have the same problem. I do know I need a new map sensor and probably a good cleaning to my throttle body but I also agree with 001stunta^^ check your sensors and clean them if needed I have to do the same

 

[F23A1AT]

I'll clean them out Tuesday, hopefully that will solve it.

I don't think the problem could be alternator associated because it is about a year and a half old. But that doesn't mean it couldn't be.

 

[kn0x47]

vacuum leak? my gf's cg would drop down to 250rpm at idle for a long time now. i recently just found the vacuum hose going to the IACV was cracked

 

[acedomain]

Another problem I had in the winter was the idle going up High like 1500 -2000 rpm and staying there and eventually dropping an sometime bouncing back and forth in between 800 to 2500 rpm an sometimes it was my map sensor came loose or acting up because I need a new one the clip on mine is broken so it slips out here and there. The other day it rained and some how got wet I think and my car was acting crazy it kept losing acceleration and I realized it was disconnected with all these symptoms I believe the map my be the cause of it all

 

[F23A1AT]

Something I forgot to mention before was when I kicked the gas pedal to keep it from stalling on me was that it would jump up to around 1400 hundred, hover then drop back sown really low again. I'm definitely going to check for vacuum leaks on it too. I had an issue a few times now where I'd get the surging associated with a vacuum leak.