Car dies at a stop while driving

1994redGT

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Hey guys. So I had posted a thread a week ago about buying a 1994 mustang gt with 200,000 miles on it. Well, i bought it. And I got it home and cleaned it up. Now, I have a few issues.

Troubleshooting steps taken.
- fixed a few loose vacuum lines
- replaced ECT (it was throwing a 116 code)
- GOING to replace fuel filter tomorrow.
- Reset computer by pulling negative
- While engine is at idle, I disconnected the IAC and the engine died

!!Note: the engine is now giving a 111 code. So it doesnt think anything is wrong, also no CEL

I plan to do the following tomorrow
- fuel filter
- spark plugs
- clean MAF and IAC
- new air filter

So this is the problem.
When I start it (cold) it will idle just fine. BUT, when I drive around and come to a stop, it will slowly stall out. (lights and electric is still on). I also tried to just let it sit and idle (cold). I waited until it warmed up. I then hit the gas in neutral and it AGAIN came down in rpm and stalled out. I also have a video of what is doing. I can upload that if it helps

Any suggestions will be appreciated. Thank you.


Video of issue: I caused the rpms to raise to 1500 and 2000 but the stumbling at low idle was the car not me

[video]https://youtu.be/xXlwiMICPS0[/video]
 

kb1982

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Pull a vacuum line off and create a big leak and see if it still does it. If it doesnt stall out then, pull your iac off and clean it.
 

JKady

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Clean/replace your IAC and clean your throttle body. Mine did that same song and dance with the stalling at lights etc... I replaced the IAC, cleaned the throttle body and quadruple checked that I had no vacuum leaks (I pulled the upper intake and pared it down to 4 vacuum lines total since mine is de-smogged) and then reset the idle. Runs perfect now.
 

CC'S95GT

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Code 111 is normal and means the computer is working correctly.
It sounds like the engine is fine when in open loop the stalls out when it goes into closed loop.
Have you ck'd fuel pressure yet?
The distributors are known for going out when the engine gets hot but I don't think that's your problem yet.
 
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1994redGT

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Ok update. Thanks everyone for the replies. I just checked the fuel pressure. And it definately shot out..that should be fine. Then I read that with the IAC disconnected it should run. So I followed the steps for a base idle reset
But first. I cleaned the maf , IAC, throttle body and put a air filter on. Now he base idle reset left me with a car that will now idle around 800 to 700... Nice. But after a few minutes this idle starts to surge. Not die...just surge. Then once and a while it will stall again. I'm about to buy some spark plugs and possibly an IAC. I can return the part if it doesn't help
 
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1994redGT

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Another update. So i found a small vacuum hose that wasnt connected. I hooked that up. Then replaced the IAC. I did another base idle reset. AND it runs alot better. But still surges every once in a while. Also, the oil pressure gauge twitches in the normal range. But, when it surges the oid pressure gauge will dip very low on the low side of the surging. I have not replaced the fuel filter or spark plugs yet. That will be for another sunny day. But, Im going to guess that these two parts are the original with 200,000 miles on them. This might help
 
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1994redGT

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Just took it for a drive and it started acting up again. So I'm pretty convinced this only occurs when the car is in closed loop mode. Right after a cold start it is fine. Then after driving. It gets worse. Could this be a bad o2 sensor?
 

JKady

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Possible, I know new plugs also went a long way toward curing my surge problem, Autolite 25's gapped on the tight side of the stock spec.

Being that it only happens in closed loop I would definitely poke the o2's with a meter and see what they're reading. Also make sure you don't have exhaust leaks up stream from the o2's.
 

87hurricane

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Have you set or checked your tps voltage? If its out of wack, you'll definitely get a surge at idle. Same goes for MAF voltage.
 
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1994redGT

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Do you mean car voltage in general or tps? I haven't double checked with a meter but the gauge says the voltage is good. I also checked the TPS voltage while messing with base idle. It sits right now at 1.0V. I also got a check engine light for a minute or two today while pulling into the gas station. I checked codes and got a 314 with KOER. I guess tonight I will go through and check alternator voltage and maf voltage
 
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1994redGT

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sorry this should have been said way earlier. it is completely stock except cold air intake. It even has smog / egr stuff
 
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1994redGT

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SOLVED

I doubt any one cares. BUT, i fixed the idle issue. I did a base idle reset. Then did fine adjustments with the set screw located on the TB. I also had to advance timing because it was heavily retarded. After all of this, it no longer surges. Still needs to fine tuning. If anyone else has this problem PM and i can try to help.
 

lwarrior1016

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I doubt any one cares. BUT, i fixed the idle issue. I did a base idle reset. Then did fine adjustments with the set screw located on the TB. I also had to advance timing because it was heavily retarded. After all of this, it no longer surges. Still needs to fine tuning. If anyone else has this problem PM and i can try to help.

I didn't help any with troubleshooting, but I am glad you got it all worked out. I know you haven't been around too long but for future measure just remember (this may sound a little gay, but its not intended too lol) everyone here cares about one another. I haven't been here long, but I can say that this place is very welcoming and people always check back in to see if an issue was resolved. Spend a little more time here, I think you'll like it.
 

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