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Discussion Starter #1
2000 V6 3.8 Manual

My car runs strong, good power and good take off and throttle response. Recently bought this car knowing of this problem. The car when (slowing down, shifting manual slowing with clutch, letting off gas for a few seconds or stopping/braking to stop sign or in traffic, turning corners) my rpms drop down low quickly to around 500 I think and the car shuts off. It does this most of the time after the car has warmed up. usually if I start car first thing in day it will not cut out on me until the car warms up or after 5 miles or so of driving. If I either shift the manual to neutral and give it gas while stopped or turning corners it wont shut off.

Today it cut on me and the battery was dead when I tried to restart it . I tested it and replaced the battery because it was bad thinking that was the problem but the problem continued.

While changing spark plug wires one of the wires was not attached on a plug so I assumed that was why I was having problems but that didn't help although it did give me more power and less erratic rpm and stuttering while driving and gas smell gone.


I have replaced the TPC, I swapped IAC with another used one that came of a junk car, changed spark plug and wires, and replaced the battery. Tested the MAD sensor by tapping on it while car is running and I also unplugged it and drove it and Im still having problems.

I'm pulling my hair out trying to figure what the problem may be. I'm thinking maybe replace the EGR valve and the Fuel Fiter because those look pretty old. Any help would be greatly appreciated

---------- Post added at 08:49 PM ---------- Previous post was at 08:40 PM ----------

To. add. Coil pack seem good. Took each spark wire out and got a nice blue spark out of each one

Car will just die down when slowing down or coming to stops or hard braking. RPM drops low first then it does out quickly.
 

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King Trashmouth
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Generally when you have a stalling condition at tip out/closed throttle like that, it's usually some sort of airflow issue. You've got part of it with the IAC and TPS (though be careful a junkyard IAC might not rule it out), other things I would check would be the throttle stop, MAF sensor, and possibly the most difficult, a vacuum leak. These cars are getting older and it's easy to get a leak, especially in the PCV system. Too much airflow can make it go too lean and die out.
 

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Generally when you have a stalling condition at tip out/closed throttle like that, it's usually some sort of airflow issue. You've got part of it with the IAC and TPS (though be careful a junkyard IAC might not rule it out), other things I would check would be the throttle stop, MAF sensor, and possibly the most difficult, a vacuum leak. These cars are getting older and it's easy to get a leak, especially in the PCV system. Too much airflow can make it go too lean and die out.
Old it is! HAHA

What is the throttle stop? I was told I could test the MAF by unplugging it and driving it to see if that fixes anything but for me it did the same cutting off. I also tapped on it while the car was idling and the car didnt make any change to idle.

This car had my ears full attention listening for leaks and i also did spray around houses and such but I didnt hear or see any leaks
 

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I would check for vacuum leaks first, easy to do.
 

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King Trashmouth
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Old it is! HAHA

What is the throttle stop? I was told I could test the MAF by unplugging it and driving it to see if that fixes anything but for me it did the same cutting off. I also tapped on it while the car was idling and the car didnt make any change to idle.

This car had my ears full attention listening for leaks and i also did spray around houses and such but I didnt hear or see any leaks
Throttle stop is also known as a throttle screw or throttle adjustment screw. That's how you adjust how much air is going through the throttle when it's in the "closed" position. There should be a procedure for setting it, though I don't recall it for the 3.8s.

Unplugging the MAF is a pretty coarse check. You can remove it and check visually for any signs of fouling/damage, but it's tough to diagnose without logging data.

Vacuum leaks are a total bitch to check. Everyone has their secret sauce for finding them, from carb cleaner to propane to smoke machines. I will say you can make a decent smoke machine at home using some lamp wicks, a heating element of your choice (even a suitable sized soldering iron), compressed air and glycerin for your smoke fluid.
 

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Discussion Starter #6
I would check for vacuum leaks first, easy to do.
How do I check for that the easiest way as you say?

---------- Post added at 12:26 AM ---------- Previous post was at 12:24 AM ----------

Throttle stop is also known as a throttle screw or throttle adjustment screw. That's how you adjust how much air is going through the throttle when it's in the "closed" position. There should be a procedure for setting it, though I don't recall it for the 3.8s.

Unplugging the MAF is a pretty coarse check. You can remove it and check visually for any signs of fouling/damage, but it's tough to diagnose without logging data.

Vacuum leaks are a total bitch to check. Everyone has their secret sauce for finding them, from carb cleaner to propane to smoke machines. I will say you can make a decent smoke machine at home using some lamp wicks, a heating element of your choice (even a suitable sized soldering iron), compressed air and glycerin for your smoke fluid.
I seriously dont think its a leak.

Have you ever heard of forscan data logger? I was thinking about buying that one

and I believe the 2000 mustang doesn't have a idle set scree because its all computerized
 

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I use forscan and love it. Also yes they do have a throttle stop screw, it controls base idle in case the iac doesnt work and Im sure the ecu assumes that the throttle body is at a certain angle and sets the iac accordingly.

Stalling when pushing in the clutch was a big issue for a lot of 99-00 gts and usually the fix was the adjust the throttle stop screw.
 

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6 Cylinduh, Really Bruh?
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Anytime I've had Rpm issues like this where it drops stupid low and does, stays up way too high, or gives me issues it was the iac. That dumb thing is so weak on these Fords I hate it. Had this issue on my mustang twice and my old Ford explorer twice. Every time the iac was gunked or shot.

You can pull it and clean it and reinstall and see if the issue goes away. Cleaning is extremely temporary and will only last a day or two. Remedy is to replace it. Go motorcraft. Trust me.

You can also clean the maf. Use maf cleaner only. Actually on my explorer when I ran k&n oiled crap I had oil get on the maf. Cleaning it revived it but the iac usually does this havoc.

Sent from my SM-G920T1 using Tapatalk

---------- Post added at 09:39 AM ---------- Previous post was at 09:36 AM ----------

Also I say you say you swapped iac from a junk car. Try new.

Always remember to reset the computer properly. I Learned this one the hard way. Don't just replace an electronic component and try again. The computer must be reset to learn the new procedure. I typically unplug the battery for 5 mins. Reconnect. Let it idle for 5 minutes. Then go and drove normally for a few miles. This has always worked for me. Hanging Rpms or dropping rpms drive me up the wall.

Sent from my SM-G920T1 using Tapatalk
 

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Anytime I've had Rpm issues like this where it drops stupid low and does, stays up way too high, or gives me issues it was the iac. That dumb thing is so weak on these Fords I hate it. Had this issue on my mustang twice and my old Ford explorer twice. Every time the iac was gunked or shot.

You can pull it and clean it and reinstall and see if the issue goes away. Cleaning is extremely temporary and will only last a day or two. Remedy is to replace it. Go motorcraft. Trust me.

You can also clean the maf. Use maf cleaner only. Actually on my explorer when I ran k&n oiled crap I had oil get on the maf. Cleaning it revived it but the iac usually does this havoc.

Sent from my SM-G920T1 using Tapatalk

---------- Post added at 09:39 AM ---------- Previous post was at 09:36 AM ----------

Also I say you say you swapped iac from a junk car. Try new.

Always remember to reset the computer properly. I Learned this one the hard way. Don't just replace an electronic component and try again. The computer must be reset to learn the new procedure. I typically unplug the battery for 5 mins. Reconnect. Let it idle for 5 minutes. Then go and drove normally for a few miles. This has always worked for me. Hanging Rpms or dropping rpms drive me up the wall.

Sent from my SM-G920T1 using Tapatalk

I cleaned the original IAC but I didnt reset the computer. I dont think I seen a difference because after 10 mins or 5 miles of driving car problem comes back. The junkyard IAC I put on , I did reset the the computer. Same thing happen what I describe below LOL

Check this! What is weird when I test the car I always drive to my Autozone down the street maybe 5 miles away. But I have to turn right directly into the parking lot off a busy street. Like clockwork it cuts off EVERYTIME when I make the turn into the parking lot and then the troubles begin again. The drive there is a straight line shot except for a few stoplights.


I dont want to spend a ton on the IAC and it not be the problem. The junkyard has a 2004 mustang very clean looking there with a IAC on it. I'm assuming that have to be good. The car looks like it was driving and just got in a accident and car junk so Im assuming the IAC was fine before. IF this junkyard IAC works then i will buy a new one. They are only $5. Might as well grab a egr valve to. If those work then I will buy new which I plan to anyway but I want to do part by part in order to know what the problem was.
 

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First thing I would do is check out fuel trim when the car starts to act up. If it could be datalogged that would be even better.
 

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I use forscan and love it. Also yes they do have a throttle stop screw, it controls base idle in case the iac doesnt work and Im sure the ecu assumes that the throttle body is at a certain angle and sets the iac accordingly.

Stalling when pushing in the clutch was a big issue for a lot of 99-00 gts and usually the fix was the adjust the throttle stop screw.
Eleven years ago after installing a new throttle body my 2000 GT was having all sorts of idling problems when I slowed and stopped. When I let off the throttle RPMs would surge up and down before the engine died. It took one-sixteenth turn clockwise of the throttle body stop screw to fix it. The IAC needs time to react. By-pass air around the butterfly valve in the throttle body gives it that time. I haven't needed to adjust it since.

The stop screw is not an idle adjustment screw. Idle is set by the computer. If you change the idle when turning the screw you've gone too far. Playing around with the stop screw it took a little over one full turn to change the idle on my car.

I've had to clean the IAC once a few years ago. It has worked fine ever since.
 

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I use forscan and love it. Also yes they do have a throttle stop screw, it controls base idle in case the iac doesnt work and Im sure the ecu assumes that the throttle body is at a certain angle and sets the iac accordingly.

Stalling when pushing in the clutch was a big issue for a lot of 99-00 gts and usually the fix was the adjust the throttle stop screw.
Eleven years ago after installing a new throttle body my 2000 GT was having all sorts of idling problems when I slowed and stopped. When I let off the throttle RPMs would surge up and down before the engine died. It took one-sixteenth turn clockwise of the throttle body stop screw to fix it. The IAC needs time to react. By-pass air around the butterfly valve in the throttle body gives it that time. I haven't needed to adjust it since.

The stop screw is not an idle adjustment screw. Idle is set by the computer. If you change the idle when turning the screw you've gone too far. Playing around with the stop screw it took a little over one full turn to change the idle on my car.

I've had to clean the IAC once a few years ago. It has worked fine ever since.
You are correct my friend, I wasnt thinking when I posted lol. I always think of you when I see threads like this because you were always setting people straight. I had the same problem when I had my 00 gt eons ago and you were there telling me the same thing lol.
 
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