ok...narrowed down the rpm drop problem

JonJon · Mar 10, 2004

00VERT GT said:
That's exactly what i didn't want to start doing...replacing things one part at a time.
Sorry for the ignorance but where is the screw that you guys were talking about to adjust idle?

I assume they mean this :

(Thanks MustangWorld)

00VERT GT · Mar 11, 2004

Thanks JonJon i'll try messing with that this weekend and i'll post my results on this thread.

00VERT GT · Mar 15, 2004

yeah um that screw is nowhere to be found on my stock Tb. Anyways isn't the idle all controlled by the computer anyways or even my chip?

Thinking about buying a new MAF anyone know of any good sites that sell them for cheap?

JoeySperz · Mar 15, 2004

My guess would be the alternator or your MAF may not be functioning correctly. The reaon your RPMs drop when you turn your wheel and brake is because the pump is run off of the same belt your alternator is run off of, which is why you will see your lights dim, or in some of your cases, other more important things malfunction. I would get it checked before you jumped the gun and bought the MAF. It would suck if you bought it and that wasn't the problem, huge waste of money. Check out www.kmodifiedracing.com for the MAF sensors, they have some good prices. You probably have to email them at domestics@kmodifiedracing.com because i dont think they are on the site yet. Anyway, GOOD LUCK WITH EVERYTHING!

YardSpecial · Mar 15, 2004

My 02 with only 13K miles on it does the SAME dam thing, insane low idle !

I have a auto also.

GTblack_00 · Mar 15, 2004

I have to post here,

IMHO, ford has the drive idle speed adjusted too low, it is set to 560 while in drive from the factory. If they bumped it up to say another 20-25 r's and played with the dashpot decay settings (the settings that control how fast the r's drop and how it settles to idle), our cars wouldnt do this. It is basically a tuning problem from factory.

00VERT GT · Mar 15, 2004

GTblack_00 said:
I have to post here,

IMHO, ford has the drive idle speed adjusted too low, it is set to 560 while in drive from the factory. If they bumped it up to say another 20-25 r's and played with the dashpot decay settings (the settings that control how fast the r's drop and how it settles to idle), our cars wouldnt do this. It is basically a tuning problem from factory.

Thanks for the advice i think i'll try and get my voltage checked...assuming that would tell me if my alternator was bad?? And your explanation GTBlack is one of the best so far...i just wish Ford would own up to it or at least give us a fix. Going to try Autozone today see if they will check my Alternator.

djtech · Mar 15, 2004

You should check your key on, ignition off TPS voltage.

Carl & everyone you should not have to adjust your idle screw if your computer/tps/iac is working correctly. Going from memory I remember setting my TPS at .98x volts with key ON and motor not running. You should then able able to floor it (just open the butterfly valve) and see your TPS go up to 4.6V's.

If your values are off set the ignition off to .98X and disconnect the battery for 5 mins. Then start the car and let 'er run for a while. Then take her for a spin and see if it makes a diff!

00VERT GT said:
Thanks for the advice i think i'll try and get my voltage checked...assuming that would tell me if my alternator was bad?? And your explanation GTBlack is one of the best so far...i just wish Ford would own up to it or at least give us a fix. Going to try Autozone today see if they will check my Alternator.

00VERT GT · Mar 19, 2004

ok checked alternator...it's fine. So I guess it isn't electrical. THAAAAAAAAAAAAAAAAT's great.

On another note it looks like more people are coming forward with same problem. Hopefully one of us finds a fix.

JonJon · Mar 19, 2004

we need a fix already
My RPM dropping is worse now after 75mm tb... happens more often. I took out the 1/2" intake spacer I had also, made no difference (reset computer).

I've never stalled out, but dropping to 600 and rev'ing up to 1000 randomly is becoming obnoxious. It seems to be getting worse?

YardSpecial · Mar 19, 2004

Will ask my Ford ASE Tech, maybe he knows somthing??

Mine is really low and I don't like it !

Problem raiseing the idle is the car will push the brakes even MORE !!

Stang as really low stall, so that probly why they idle so low??

My truck with same engine and trans does not do that.

hognutz · Mar 19, 2004

I bought a new plenum tb combo off ebay. it came complete with new IAC. I swapped it on and had this same problem. swapped my old IAC on and the problem is gone.

Where did you buy the new IAC valve? I notice that the one that came on my plenum was not the exact same part that was on my car. I dont' know if it was aftermarket or different year.

Jesus · Mar 19, 2004

Not that this helps, but my 2003 5 speed has done this pretty much from day one. It has only completely stalled twice, and that was on the same day quite a while ago. RPMs usually drop to around 500-550 rpm upon breaking before coming back up to like 700 idle.

djtech · Mar 20, 2004

and it's so damn easy to check TPS voltage

00VERT GT said:
ok checked alternator...it's fine. So I guess it isn't electrical. THAAAAAAAAAAAAAAAAT's great.

On another note it looks like more people are coming forward with same problem. Hopefully one of us finds a fix.

00VERT GT · Apr 5, 2004

b-u-m-p

00VERT GT · Apr 26, 2004

forgot to add that sometimes when i hit second and the rpms start dropping i can floor it and the car won't move. It just sits there and coasts like im' not even on the throttle. I asked my mustang shop tech and he said it is a bad maf. Is that possible?? I didn't think the maf had anything to do with the throttle f'n up.

NaplesBill · May 25, 2006

Well, I have an '03 Explorer with the same motor as the 99-04 GT. I had a problem very much like everyone here is describing. It started a couple of days ago and just kept getting worse. Today I had to hold the gas and brake everytime I stopped to prevent the engine from stalling.

I decided to take a look at it tonight. I have an engine cover and when I removed it I kept hearing this sucking sound. It sounded like it was coming from the intake manifold. It turned out that the breather tube that connects from the passenger side valve cover to the intake plenum had a hole in it. I have no idea how the hole got there but I replace the elbow where the hole was and the problem is fixed.

It's the large breather tubing that elbows right at the intake plenum. There are two small cooling lines that connect at the same area on the plenum. It would stand to reason that a smaller whole or leak would cause less severe but similar symptoms.

gtstangau · May 25, 2006

They need to come up with some way to fix it, because mine always does that! It is so annoying hearing it rev up and down like that, or stalling out at redlights and stuff. Seems like alot of people have the same problem, but the only answer I ever hear is replace the IAC. (wich is usually a very short term fix for my car) Is there anything else it could be?

JohnnyG3 · Apr 28, 2018

Anyone have an update on this problem. Having same issue and still can’t figure it out!!

JohnnyG3 · May 16, 2018

You ever solve this?

ok...narrowed down the rpm drop problem

JonJon

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