Ford Mustang Forum banner

Mustangs stalls when clutch pushed in @Higher RPM

16018 Views 18 Replies 5 Participants Last post by  Warghost
I've had an issue with my 2004 Mustang GT 5-speed for a while now. Heres a scenario. I'm driving down the road accelerating in third gear, the RPM's get to 3000rpm and I decide to shift to fourth gear. If I hold down the clutch without actually engaging into 4th gear, the rpms drop (like they should) but the needle will fall to zero and the engine dies. Normally I would engage the clutch and down shift or whatever, but the engine should only drop to its set idle right? This problem normally only happens at speeds above 40mph. The car idles fine, and starts fine (most of the time). The car only has 23,000 mile on it and and everything else seems to work fine. But sometimes the engine stall catches me off guard, and since the power steering and pwr brakes shut off, it could be dangerous if I can't pop th eclutch fast enough to get the engine going again.
Do you have any suggestions or anyone had this problem before?:headscratch:
Not open for further replies.
1 - 11 of 19 Posts
I actually cleaned out the IAC yesterday, it looked pretty clean but still cleaned it out anyways. It unfortunately didn't change anything. All the vacuum lines look good as well. As far as the chip goes, there isn't one installed unless the previous owner flashed the computer. I order the SCT X3 two weeks ago and should be at my door step tomorrow (May 2). If there was already an aftermarket tune (which I hope not, since I've been running 87) on the computer, would my new SCT tuner detect it? Or do you think the new program I'm going to install might help the problem?
I thought I read that the IAC is preset for a certain idle and the only way to change it is through the computer, so maybe a new tune would do it. Does this sound right?
Do you have any other ideas of what might be causing this. The car won't ever stall if say, when I'm slowing down off the interstate and braking, if I let the RPMs drop down while still in gear and then push the clutch once the RPM's are down around 1500, then I can roll all the way to a stop with the clutch pushed in without it stalling. This is the way I normally drive and have gone months without a stall. At first I was thinking that the stall problem was just the way I was driving. In fact, thats what the dealership I bought it from told me, but none of my other manual cars had ever done that so I figured they were full of ****.
Have you checked the mechanical idle stop on the throttle body? It almost sounds like it may be adjusted all the way closed or close to it. Perhaps the previous owner didn't like the idle hang that the IAC causes and reset the mechanical stop in an attempt to drop the idle faster. I recently installed a 70mm throttle body on my 02 and it required some adjustment of the mechanical screw to get it to idle correctly. In my case I found that the air for idling appears to be supplied both by the butterfly and the IAC. Be aware that if you adjust the idle screw you may need to adjust the TPS sensor to have the correct setting at idle.
If the butterfly is incorrectly adjusted maybe the IAC cannot respond properly under the shifting conditions????

Good luck
The cars RPM's do seem to drop fast if thats what your talking about idle hang. The car idles fine, so would adjusting this mess with that? Do you adjust that screw on the TB and which way would I want to turn it?
Also, ClayXmach1, I don't have an actual cold air intake, but have a shaker hood like on your 04 Mach (sweet car by the way). This is the closest I have to colder air. The intake pipe/tubing is stock from the box. My when the Roush Shaker hood was install they changed the MAF position. I thought there was only one way MAF fits in. How do you turn it 90 degrees?
Well, I got my SCT-X3 tuner today:myhappydance:. I still have about a 1/4 of 87 in the tank, so I want to run this gas down more, and switch to the 91 before I flash the computer for 91 octane. I did want to try out the tuner so I used its dtc code reader. The only code it found was P1233 which is no signal from the fuel pump. I took the FP fuse out like I read to do, so that P1233 was expected. No other errors though.
I've been doing none stop research on this stalling thing and can't pin point it, except it only seems to happen at speeds above 40mph. I'd just go and replace all the emmisions components if I could but I'm short on cash right now. Do you think the TPS or EGR (Exhaust Gas Recirculation) might be part of the problem?
First off, thank you for the great info and the time you have taken with looking into my problem! I looked at the adjusting screw and it doesn't appear anyone tampered with it. It is threaded out quite a ways too. Right now, I'm going to test the TPS and see where that is at. I'll let you know what I find out. Also, I read in my Chilton manual that the EGR can cause idle issues too, depending on the flow through it. Any takes on this?

Thanks again:thumbsup:
Alright, I tested the TPS. I didn't have an assistant with so I just turned the throttle on the TB myself. When I turned the key on, the TPS read 1.00 volts. At full throttle, it read 4.62 volts.
When reflashing your computer, it's recommended that you pull your fule pump fuse, and/or any other acc. the might turn on and draw power when uploading/downloading the new tune. Since I was just checking for dtc code, I probably didn't need to pull the fuel pump fuse, but did it anyways. After putting the FP fuse back in, the dtc checked no errors.
So if I try adjusting the throttle body adjustment screw, would it be best to have the car running to see how it reacts to the change, instead of adjusting and finding out after I turn the key for the first time?
The Tune I loaded was a custom tune from the dealer. I see you can data log with these tuners. Do you think I might find a clue to this problem if I data log and let the car do its stall thing? Ive been thinking about just replacing the IAC but cleaning it didn't help so I don't want to waste the money, if the problem is something else.

Also, last night, the car stalled only the RPM's weren't high. I was driving a 55 and shifted into 5th gear. Normally I drive in 4th at this speed cause the RPM's sit to low in 5th. But I did have it in 5th,
RPM's at about 1200, at 55mph, I pushed the clutch in approaching a stop light and it died. I just just threw it in 4th and popped the clutch and she ran again, but it did die during a different scenerio. It seems like it won't idle if the gear is set to low for the speed when the clutch is pushed in too. But no matter what gear your in, as long as the clutch is pushed in, it should idle, right?
1 - 11 of 19 Posts
Not open for further replies.