Idle drop while coasting

slo984now · 03-06-2008, 01:04 AM

I got stuck in traffic the other day while coming down a hill. Since I was able to just let off the brake to move forward, that's all I did for about a half mile. Every time I let off the brake my idle would flucuate between about 200 and 800rpm. As soon as I stopped it would idle normally though. I just dropped off my son and did the same thing. As soon as I start rolling the idle flucuates and as soon as I stop it goes back to normal. I was thinking it might be something in the tune. But someone suggested the power steering pump might be changing on the engine. Any other ideas?

STAMPEDE3 · 03-06-2008, 08:41 AM

Clean the IAC first.

01 Cobra · 03-06-2008, 08:59 AM

Quote:

Originally Posted by STAMPEDE3

Clean the IAC first.

+1 made a world of difference on mine.

eddieveddie85 · 03-06-2008, 02:52 PM

Mine does the same thing i'm also curious to know.

tcchubb · 03-06-2008, 02:55 PM

hey mine was doing the same thing. what my problem was is the Mas air came lose. i got it all back together and have not had the problem since. hope it helps

SVECobraR · 03-06-2008, 03:19 PM

Quote:

Originally Posted by tcchubb

hey mine was doing the same thing. what my problem was is the Mas air came lose. i got it all back together and have not had the problem since. hope it helps

did this work for the op and second poster?

eddieveddie85 · 03-06-2008, 03:20 PM

no i havent corrected this problem

grey01cobra · 03-06-2008, 03:26 PM

same problem here. Replaced Iac and cleaned maf with no luck.

slo984now · 03-06-2008, 05:38 PM

Quote:

Originally Posted by STAMPEDE3

Clean the IAC first.

It's already been cleaned.

Quote:

Originally Posted by tcchubb

hey mine was doing the same thing. what my problem was is the Mas air came lose. i got it all back together and have not had the problem since. hope it helps

I checked that too. My MAF sensor is actually mounted in the blower pipe. So it's really in there good.

It's just weird that it only does it when I'm rolling. As long as I'm sitting still it idles perfect.

cobraetti · 03-06-2008, 05:43 PM

check for codes, its the best way I know if you have a tuner or go to a auto parts store

slo984now · 03-06-2008, 06:25 PM

I have a tuner. The only code is the P1000.

STAMPEDE3 · 03-06-2008, 07:26 PM

Quote:

Originally Posted by slo984now

It's just weird that it only does it when I'm rolling. As long as I'm sitting still it idles perfect.

Check voltage on TPS, if it is at .99 or so lower it to about
.97 and give it a shot.

darksidestalion · 03-06-2008, 07:33 PM

I noticed the same thing when i first got my cobra, But is has a hydraulic booster so its going the fluctuate when appling and letting off the brake pedal

STAMPEDE3 · 03-06-2008, 07:47 PM

Quote:

Originally Posted by darksidestalion

I noticed the same thing when i first got my cobra, But is has a hydraulic booster so its going the fluctuate when appling and letting off the brake pedal

It shouldn't and if it did it for sure shouldn't go from 200-800RPMs.

It is searching for idle.

However, there is a mode called dashpot mode which raises the idle when coasting with the clutch in if over
3mph is read by the VSS and the TPS is at idle position.

The TPS is supposed to be at the factory spec of .99
Sometimes lowering it a bit will cure this.

wallie40 · 03-06-2008, 07:59 PM

Maybe have your tuner check the dashpot decay.

no_slow_svt · 03-06-2008, 08:08 PM

whats p1000? random misfire?

when is the last time you changed your plugs?

slo984now · 03-06-2008, 09:24 PM

Quote:

Originally Posted by no_slow_svt

whats p1000? random misfire?

when is the last time you changed your plugs?

P1000 is an emissions code. I'm sure they're due for changing. But this is something that's been going on for awhile. I was just able to put the two together finally.

Quote:

Originally Posted by wallie40

Maybe have your tuner check the dashpot decay.

I am the tuner.

I actually have it pretty dialed in except for this one thing.

slo984now · 03-07-2008, 01:08 PM

I checked my records and the plugs have 11K on them. I picked up some new ones anyway.

qwik01cobra · 03-07-2008, 01:16 PM

My car does this and even stalls out when I put the clutch in and start slowing to a stop. IDK its pretty scary when your comming up to a stop sign or light and suprise you have no power steering or brakes lol

tcchubb · 03-07-2008, 01:35 PM

dang man hope you get this fixed.

slo984now · 03-07-2008, 04:03 PM

Mine has stalled a couple times when rolling up to a stop. But it's roughly once every couple months.

DarkMesa8 · 10-26-2009, 05:26 PM

Pulling this one from the past, and I've been fighting the problem for a while.

2001 Cobra, V2-SQ on a Lightning MAF draw through, with baffle installed away from MAF.

Cleaned MAF
New Plugs
8 New Ford COPS
Cleaned IAC
New DPFE

??? Stumped! It'll happen when crawling in traffic like described, and sometimes dies going slow in parking lots (power steering strain), and sometimes dies when coming to the light.

no_slow_svt · 10-26-2009, 06:31 PM

Quote:

Originally Posted by DarkMesa8

Pulling this one from the past, and I've been fighting the problem for a while.

2001 Cobra, V2-SQ on a Lightning MAF draw through, with baffle installed away from MAF.

Cleaned MAF
New Plugs
8 New Ford COPS
Cleaned IAC
New DPFE

??? Stumped! It'll happen when crawling in traffic like described, and sometimes dies going slow in parking lots (power steering strain), and sometimes dies when coming to the light.

its something in the tune.
ive been to different tuners and had multiple set ups on my car, with the same problem since the day i put a blower on it and dyno tune.
it never once did it with a stock tune in it.

DarkMesa8 · 10-26-2009, 07:23 PM

Its pretty embarassing having to restart your car AFTER coming to a stop.

I've been battling this off and on for almost 2 years now. Its liveable, but annoying.

no_slow_svt · 10-26-2009, 07:37 PM

yes it is annoying as hell,
it stalls when you coming down to a stop and when you push in the clutch, it dies like you turned the key off. and restarts with no issues.

i feel your pain. you want to know how i fixed mine?....lol I put an automatic in it. now it keeps that load on the motor, and it doesnt ever stall