[ddarkslayer]

I have a 1988 mustang 5.0 with an idle surge problem Its been going on for about 6 months now so far I changed the fuel pump, the IAC, my water pump I have no vaccum leaks and it only surges when the engines warm. any suggestions will be helpful thanks

[NLorenza83]

I had a similar issue. It would only surge and idle around 1300 RPM when the engine warmed up good. To solve this I bought a new TPS. I stuck a needle through the green wire of the TPS and got an Ohmmeter. I attached the positive to the pin and the negative to a good ground. I think I used the EGR spacer. Then I literally turned my TPS with my finger until the voltage consistently read between .91 and .94 at idle. The TPS was really sensitive when I turned it so I had to do it really slowly. Then another thing I did was make a minor adjustment at the throttle body. That way the car was normally idling around 700 and when it would surge the surge would make it idle just below 1000 as opposed to 1300-1400.

I have an 87' with SD though. So if yours is MAF I don't know what to tell you.

[87FloridaGT]

Originally Posted by NLorenza83 Then another thing I did was make a minor adjustment at the throttle body. That way the car was normally idling around 700 and when it would surge the surge would make it idle just below 1000 as opposed to 1300-1400.

Wouldn't this just be a bandaid and still hide the real problem? I wouldnt recommend doing this

[1slo5.0]

Originally Posted by ddarkslayer I have a 1988 mustang 5.0 with an idle surge problem Its been going on for about 6 months now so far I changed the fuel pump, the IAC, my water pump I have no vaccum leaks and it only surges when the engines warm. any suggestions will be helpful thanks

Idle issues are common on these cars, especially 5-speed cars. EGR Valves, Idle Air Bypass solenoids and Throttle Position Sensors are common causes. A bad connection with the 10 pin (salt and pepper shakers) black and white engine electrical connectors can also cause poor idle quality. To ensure a good connection on the 10 pin connectors a little modification can be done which is fairly easy and will cure some surging and hanging idle issues on 86-93 Mustangs and should be the first thing done when tackling any idle issues.

10 Pin Connector modification:

1. Take the 10 pin connectors apart (salt and pepper shakers).

2. use a pick like tool to spread the male terminals open more so they make better contact. In the center of each male terminal there is a small seam and seams down the sides of the terminal which allows you to spread them open.

3. Apply some dielectric grease to the terminals

4. Plug the connectors back in.



Throttle Position Sensor (TPS) adjustment:

Without the proper adjustment, the throttle position sensor (TPS) will give the computer false reading as to the exact throttle opening. A false reading will limit wide open throttle performance. A voltage reading must be taken using a digital volt/ohmmeter (DVOM) with the Key On/Engine Off and with the Key On/Engine Running.

The TPS is located directly on top of the throttle body and is adjusted by loosening the two phillips mounting screws and swiveling the sensor until the highest reading is found. It may be necessary to elongate the holes with a small drill bit or small file to achieve the desired reading. The spec range for Key On is from .88 to 1.0 volt; shoot for the .90 to .98 volt. Make sure voltage reaches/exceeds 2.71v at WOT.

Incorrect Throttle Position Sensor (TPS) voltage will result in reduced performance including a possible hanging/surging idle. The best way to take a TPS voltage reading is by using two safety pins through the wires coming from the sensor. The positive lead is attached to the green wire, while the negative goes to the black wire. Always ground the meter through the sensor's black wire. This gives a direct, and more
accurate ground into the computer.







Resetting the base idle:

Clear the computer's idle memory by disconnecting the battery for 20+ minutes.

-Disconnect the Idle Air Bypass solenoid
-Reconnect battery
-Start engine and set idle speed to desired RPM with idle screw on throttle body
-Turn off engine and reconnect the air bypass solenoid
-Set TPS voltage between 0.90 - 0.95 volts with a digital volt meter
-Start engine and let it idle for 2 minutes with no accessories on.
-Turn off engine for two minutes
-Start engine again and run for 2 minutes with every accessory turned on.
-Turn engine off again.

[87FloridaGT]

Originally Posted by Darrell Idle issues are common on these cars, especially 5-speed cars. EGR Valves, Idle Air Bypass solenoids and Throttle Position Sensors are common causes. A bad connection with the 10 pin (salt and pepper shakers) black and white engine electrical connectors can also cause poor idle quality. To ensure a good connection on the 10 pin connectors a little modification can be done which is fairly easy and will cure some surging and hanging idle issues on 86-93 Mustangs and should be the first thing done when tackling any idle issues. 10 Pin Connector modification: 1. Take the 10 pin connectors apart (salt and pepper shakers). 2. use a pick like tool to spread the male terminals open more so they make better contact. In the center of each male terminal there is a small seam and seams down the sides of the terminal which allows you to spread them open. 3. Apply some dielectric grease to the terminals 4. Plug the connectors back in. Throttle Position Sensor (TPS) adjustment: Without the proper adjustment, the throttle position sensor (TPS) will give the computer false reading as to the exact throttle opening. A false reading will limit wide open throttle performance. A voltage reading must be taken using a digital volt/ohmmeter (DVOM) with the Key On/Engine Off and with the Key On/Engine Running. The TPS is located directly on top of the throttle body and is adjusted by loosening the two phillips mounting screws and swiveling the sensor until the highest reading is found. It may be necessary to elongate the holes with a small drill bit or small file to achieve the desired reading. The spec range for Key On is from .88 to 1.0 volt; shoot for the .90 to .98 volt. Make sure voltage reaches/exceeds 2.71v at WOT. Incorrect Throttle Position Sensor (TPS) voltage will result in reduced performance including a possible hanging/surging idle. The best way to take a TPS voltage reading is by using two safety pins through the wires coming from the sensor. The positive lead is attached to the green wire, while the negative goes to the black wire. Always ground the meter through the sensor's black wire. This gives a direct, and more accurate ground into the computer. Resetting the base idle: Clear the computer's idle memory by disconnecting the battery for 20+ minutes. -Disconnect the Idle Air Bypass solenoid -Reconnect battery -Start engine and set idle speed to desired RPM with idle screw on throttle body -Turn off engine and reconnect the air bypass solenoid -Set TPS voltage between 0.90 - 0.95 volts with a digital volt meter -Start engine and let it idle for 2 minutes with no accessories on. -Turn off engine for two minutes -Start engine again and run for 2 minutes with every accessory turned on. -Turn engine off again.

Is this stickied somewhere...very helpful stuff. Reps for you

[ddarkslayer]

I was told by a mobil mechanic that it was because I was low on coolant and because the coolant temprature sensor didn't read the coolant temprature is that a reasonable reason

[1slo5.0]

Originally Posted by ddarkslayer I was told by a mobil mechanic that it was because I was low on coolant and because the coolant temprature sensor didn't read the coolant temprature is that a reasonable reason

No

[Traidmarx]

Originally Posted by ddarkslayer I was told by a mobil mechanic that it was because I was low on coolant and because the coolant temprature sensor didn't read the coolant temprature is that a reasonable reason

that actually will happen with honda's and stuff but i've never heard of it happening in a mustang...but i can speak from experience my 92 accord i used to own would do that.


do you notice a difference in the way that it surges with the MAF unplugged?

[flattusmaximus78]

were are the 10 pin salt and pepper shakers?

[mxnate116]

Originally Posted by flattusmaximus78 were are the 10 pin salt and pepper shakers?

back of the intake. next to the egr spacer. they connect the wiring harness on the car to the harness on top of the motor

[ddarkslayer]

When I changed my fuel pump the surge fixed it self from really bad to alot better does that mean that it's one problem out of the way.

[ddarkslayer]

I also noticed when I had low coolant I had a check engine light. when I filled up the radiator the check engine light went away but it still surges at idle

[1slo5.0]

Originally Posted by ddarkslayer I also noticed when I had low coolant I had a check engine light. when I filled up the radiator the check engine light went away but it still surges at idle

Low coolant lights are common on 87-93 Mustangs. The sending units read falsely.

[grnstang]

yeah my low coolant light is always on. Also...the cap on my overflow tank wont screw on anymore (that black plastic junk). is the sensor and cap one unit by itself? i cant remember. it would be nice if i could just buy one part and i got 2 birds with one stone

[ddarkslayer]

I don't have a low coolant light anymore it was already removed when I bought the car but when I put more coolant in it the idle surge got better

[1slo5.0]

Originally Posted by ddarkslayer I don't have a low coolant light anymore it was already removed when I bought the car but when I put more coolant in it the idle surge got better

Coincidence. If your coolant was low enough to affect the ECT it would also be low enough to over heat.

[gotn20]

mines a surger lol

[1slo5.0]

Originally Posted by 87FloridaGT Is this stickied somewhere...very helpful stuff. Reps for you

It is now.

[ddarkslayer]

what do they mean turn on all accesories

[ddarkslayer]

Originally Posted by 87FloridaGT Is this stickied somewhere...very helpful stuff. Reps for you

I tried modifying the salt and pepper shaker its not an easy job if you don't have the right tool and you are forced to find something else then you would find your self using a sewing needle like me