So i recently picked up a 93 2.3l fox body with 104k miles. Today i did a tune up which consisted of new plugs, wires, and 2 new ignition coils. The car doesn't have a check engine light on and runs but sometimes when I'm sitting at the light it will just die. It doesn't stutter or anything it just dies. it will fire right up and drive with no problem but at idle for more than 2 mins or so it will shut off. It idles at around 600-700 rpms and I've checked to make sure all the wires and sensors where plugged in all the way. Any advice or help would be great.
Engine 2.3 N/a Stalls At Idle
- Thread starter 93LXFOX
- Start date
91TwighlightGT
20+ Year Stangneter 
I would start with pulling codes and seeing if anything comes up. There are a lot of reasons for a car to have a dying problem, especially when they have gotten as old as these have. The most common reasons are vacuum leaks or a dirty idle air control valve. You can try cleaning the valve, but at the vehicles age it probably would just have to be replaced if it is acting up.
The idle that you are listing is a bit low - it should be 750-800, so there is definitely an issue.
I tested the idle air control valve and checked for leaks, I checked the pcv and it was good, checked the maf sensor, and I haven’t found any air leaks in any of the lines. I’m pretty confused as to what the issue is. I adjusted the idle screw to bring it closer to 800 rpms when it’s warm. As for pulling codes wouldn’t it kick the check engine light on if it was throwing codes? I don’t have an obd1 device to check the codes and the local part stores only offer obd2 testing.
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91TwighlightGT
20+ Year Stangneter
There can be codes without a light, so you should always check. Search this site for details on how to read codes without a scanner using a paper clip.
Did adjusting the idle solve your problem?
Did adjusting the idle solve your problem?
I adjusted the idle and it idles fine I park but in drive it sits lower and still stalls. I have a scanner to check out of its throwing any codes tomorrow and I’ll go from there.
Go to the fox5.0 tech page and look for the tech/how to threads, there is a list of stuff there, look at the 'how to pull codes' thread and also the surging idle checklist, most of the stuff will apply to the 4L engine, look for the 'setting base idle' instuctions and cleaning maf and egr intructions.
I have not looked at the tech articles on the 2.3 na/turbo threads but I bet there is much info there that will be specific to the 4L family.
Also keep in mind that doing stuff like ajusting the throadel blade will have a negative effect or mask the problem because the computer controls things with input from sensors before and after the tb. There is the correct way to do it. With some changes you will have to reset the computer also. The reset intructions are also in the tech threads.
Keep us posted with codes you find and the people here can help.
I have not looked at the tech articles on the 2.3 na/turbo threads but I bet there is much info there that will be specific to the 4L family.
Also keep in mind that doing stuff like ajusting the throadel blade will have a negative effect or mask the problem because the computer controls things with input from sensors before and after the tb. There is the correct way to do it. With some changes you will have to reset the computer also. The reset intructions are also in the tech threads.
Keep us posted with codes you find and the people here can help.
update 12/24
i went and purchased a scanner because my friend only had obd2 scanners. i ran the test and the codes i received were 181c, 118c, r521, r538, and r536..
181c - fuel system at rich adaptive limit at partial throttle/ system lean
118c - engine collant temperature sensor above max voltage
521r - power steering pressure switch circuit fault.
538 r - insufficient rpm change during doer dynamic response test.
536 r - brake on/off circuit not activated.
I'm assuming the 181c is whats causing the issue which seems to lean towards the maf sensor or the map sensor. both seem to be the same direction things were going before actually running the codes. Both sensors seem to run about $80.00 each so id like to be sure which one i should buy.
118c is the coolant sensor which i felt may have been bad because the car usually doesn't go above 140 degrees when driving. The issue is there is 3 so I'm not sure which one i should change. i know there is one on the passenger side by the firewall and one in the engine block.
538r i would assume is completely connected to 181c.
521r and 536r i don't think have anything to do with the idle issue but ill slowly fiddle with those to see what happens. The power steering works and after scanning the codes i changed out power steering fluid.
i went and purchased a scanner because my friend only had obd2 scanners. i ran the test and the codes i received were 181c, 118c, r521, r538, and r536..
181c - fuel system at rich adaptive limit at partial throttle/ system lean
118c - engine collant temperature sensor above max voltage
521r - power steering pressure switch circuit fault.
538 r - insufficient rpm change during doer dynamic response test.
536 r - brake on/off circuit not activated.
I'm assuming the 181c is whats causing the issue which seems to lean towards the maf sensor or the map sensor. both seem to be the same direction things were going before actually running the codes. Both sensors seem to run about $80.00 each so id like to be sure which one i should buy.
118c is the coolant sensor which i felt may have been bad because the car usually doesn't go above 140 degrees when driving. The issue is there is 3 so I'm not sure which one i should change. i know there is one on the passenger side by the firewall and one in the engine block.
538r i would assume is completely connected to 181c.
521r and 536r i don't think have anything to do with the idle issue but ill slowly fiddle with those to see what happens. The power steering works and after scanning the codes i changed out power steering fluid.
91TwighlightGT
20+ Year Stangneter
Before you start buying a bunch of sensors, start with fixing the coolant temp sensor. If your car doesn’t know what temperature it is running, it will cause the exact problem you are describing.
I can’t link it here but google “93 mustang 2.3l coolant temp sensor” and go to the first allfordmustangs link and there is a picture showing the three temp sensor locations.
If the car thinks it is running too cool then it will richen up the fuel. Fix that, then see what comes back.
I can’t link it here but google “93 mustang 2.3l coolant temp sensor” and go to the first allfordmustangs link and there is a picture showing the three temp sensor locations.
If the car thinks it is running too cool then it will richen up the fuel. Fix that, then see what comes back.
Yeah I’m going to mess with the coolant sensor tomorrow after I change the rear shocks
So I’ve only found two on the car. I changed the one and the other one that’s in the side of the block I haven’t been able to find for sale. It’s cold out so I think driving in 30 degree weather is part of why it runs cool. When I let it sit and run with out driving the gauge will go up about half way before the fan kicks on. I can pick up maf and map sensor brand new for $100. But idk if that’s the issue. I guess it I get them and it doesn’t help I can always return them. I kind of at a loss for what the problem is and a little frustrated. Mostly frustrated because the driver side putter door handle broke today so I’m going
To order two new metal ones to replace them both this week. I’ll probably pick up New door pins too because the driver side seems to be sagging a little which played a part in the handle breaking. Well aside from the age and fact that it’s the original handle.
91TwighlightGT
20+ Year Stangneter
Yeah that door handle is a common failure. I have always reinstalled mine with bolts rather than rivets. Fortunately it isn’t too hard, although the cold snap we are in makes everything more difficult.
Definitely a good idea to take care of the pins. The feeling of a door that opens and closes properly isn’t appreciated until you’ve dealt with one that doesn’t.
So, to be clear, the sensors on the block control the temperature gauge and the fan. It appears that both those are working. The temp sensor between the injectors is what supplies information to the ecm. If you changed that then it should have fixed your coolant temp related code. I would clear the computer (disconnect battery for 10 mins) and drive it to see what comes back. If you are still having problems then pull codes again and make a decision from there.
So I replaced the map and maf sensor and it seemed ok then it just died. Pulled the code c543 which is for secondary fuel pump circuit failure. What and where could that issue be? I can hear the pump kick on when I turn the ignition to the in position but the car won’t start
91TwighlightGT
20+ Year Stangneter
The 2.3l mustangs from 91-93 use an IRCM which houses the fuel pump relay. Although there is a possibility of wiring, the relay inside the ircm is the most likely and common failure.
Ford intends for you to replace the module as a unit, however they can be drilled open and rebuilt. The module is a few hundred dollars the last time I checked.
If you are having a no start and tap on the module it will sometimes allow the car to start. If this happens it is a good indication that the relay is failing.
Ford intends for you to replace the module as a unit, however they can be drilled open and rebuilt. The module is a few hundred dollars the last time I checked.
If you are having a no start and tap on the module it will sometimes allow the car to start. If this happens it is a good indication that the relay is failing.
So the ircm was swapped by the previous owner because it’s dated 2003 on the label. I went to order one and actually order the Ecu so I swapped it anyway to see what would happen. Well of course nothing changed. The car has stated fine since that one day but it still idles rough at start up and on and off at red lights. I’m at a lost for what it could be at this point. I feel like I’m just shooting in the dark with sensors and nothings working. If anyone knows of someone close to Atlanta that I could link up with that would be awesome. I’ve had this bad boy for 3 months now and I’ve only driven it about 7-8 times. All while not running right. I just wanna cruise and enjoy the ride.
This is an old school trick for electrical problems. Sudden death is seldom fuel but usually electrical...especially if heat related. Get a can of FREEZE at an electrical supply store (computers also or Radio Shack type store). I am an old TV repair guy who also spent 50 years building Street Rods. When the engine dies one-by-one freeze the ignition parts as you try to start it. If it starts...you have found your problem. I have seen engines stumble and stutter but smooth out when the bad part was cooled. Just a thought.
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