Iac Problem
- Thread starter InMy88GT
- Start date
Did you perform the idle reset procedure when you installed the IAC?
Install IAC, unplug it. Start engine. Adjust low idle using throttle stop screw. Set to where engine barely runs smoothly.
Then shut off engine, plug in IAC, disconnect battery for 30 mins.
Hook back up, fire up car. Let idle 2 mins, then turn on accessories for extra load on engine.
I would only replace the TPS if you gave a code for it. There's a specific range the EEC needs to see and you'll get a code 23 if voltage is below 0.5v, and a code 63 if it's above 1.1v. Chasing 0.9999v is a myth that needs to die
Install IAC, unplug it. Start engine. Adjust low idle using throttle stop screw. Set to where engine barely runs smoothly.
Then shut off engine, plug in IAC, disconnect battery for 30 mins.
Hook back up, fire up car. Let idle 2 mins, then turn on accessories for extra load on engine.
I would only replace the TPS if you gave a code for it. There's a specific range the EEC needs to see and you'll get a code 23 if voltage is below 0.5v, and a code 63 if it's above 1.1v. Chasing 0.9999v is a myth that needs to die
Keep working your way through the Surging Idle Checklist and you will find and fix the problem.
What did you get for codes?
Dump the codes and see if you get a code 67 which is for the NSS circuit.
Dump codes sticky.
Look at the top of the 5.0 Tech forum where the sticky threads are posted. One of them is how to dump the computer codes. http://www.stangnet.com/mustang-for...codes-from-eec4-in-86-95-5-0-mustangs.889006/ I highly suggest that you read it and follow the instructions to dump the codes.
Code 67 –
Revised 2 Nov 2012 to add definition of the NSS functions for both 5 speed and auto transmissions
Cause of problem:
clutch not depressed (5 speed) or car not in neutral or park (auto) or A/C in On position when codes where dumped. Possible neutral safety switch or wiring problem. This code may prevent you from running the Key On Engine On tests.
External evidence from other sources claims that a code 67 can cause an idle surge condition. Do try to find and fix any issues with the switch and wiring if you get a code 67.
What the NSS (Neutral Safety Switch) does:
5 speed transmission: It has no connection with the starter, and the engine can be cranked without it being connected.
Auto transmission: It is the safety interlock that prevents the starter from cranking the engine with the transmission in gear.
What it does for both 5 speed and auto transmission cars:
The computer wants to make sure the A/C is off due to the added load on the engine for the engine running computer diagnostic tests. It also checks to see that the transmission is in Neutral (5 speed and auto transmission) and the clutch depressed (T5, T56, Tremec 3550 & TKO)). This prevents the diagnostics from being run when the car is driven. Key On Engine Running test mode takes the throttle control away from the driver for several tests. This could prove hazardous if the computer was jumpered into test mode and then driven.
The following is for 5 speed cars only.
The NSS code 67 can be bypassed for testing. You will need to temporarily ground computer pin 30 to the chassis. Computer pin 30 uses a Lt blue/yellow wire. Remove the passenger side kick panel and then remove the plastic cover from the computer wiring connector. Use a safety pin to probe the connector from the rear. Jumper the safety pin to the ground near the computer.
Be sure to remove the jumper BEFORE attempting to drive the car!!!
Dump codes sticky.
Look at the top of the 5.0 Tech forum where the sticky threads are posted. One of them is how to dump the computer codes. http://www.stangnet.com/mustang-for...codes-from-eec4-in-86-95-5-0-mustangs.889006/ I highly suggest that you read it and follow the instructions to dump the codes.
Code 67 –
Revised 2 Nov 2012 to add definition of the NSS functions for both 5 speed and auto transmissions
Cause of problem:
clutch not depressed (5 speed) or car not in neutral or park (auto) or A/C in On position when codes where dumped. Possible neutral safety switch or wiring problem. This code may prevent you from running the Key On Engine On tests.
External evidence from other sources claims that a code 67 can cause an idle surge condition. Do try to find and fix any issues with the switch and wiring if you get a code 67.
What the NSS (Neutral Safety Switch) does:
5 speed transmission: It has no connection with the starter, and the engine can be cranked without it being connected.
Auto transmission: It is the safety interlock that prevents the starter from cranking the engine with the transmission in gear.
What it does for both 5 speed and auto transmission cars:
The computer wants to make sure the A/C is off due to the added load on the engine for the engine running computer diagnostic tests. It also checks to see that the transmission is in Neutral (5 speed and auto transmission) and the clutch depressed (T5, T56, Tremec 3550 & TKO)). This prevents the diagnostics from being run when the car is driven. Key On Engine Running test mode takes the throttle control away from the driver for several tests. This could prove hazardous if the computer was jumpered into test mode and then driven.
The following is for 5 speed cars only.
The NSS code 67 can be bypassed for testing. You will need to temporarily ground computer pin 30 to the chassis. Computer pin 30 uses a Lt blue/yellow wire. Remove the passenger side kick panel and then remove the plastic cover from the computer wiring connector. Use a safety pin to probe the connector from the rear. Jumper the safety pin to the ground near the computer.
Be sure to remove the jumper BEFORE attempting to drive the car!!!
Pull the codes like Jrichker said and see if you get that code. The auto computer in itself shouldn't cause the issue, but if they just disconnected the NSS from the auto and didn't connect it up to the clutch pedal and trans it could be a problem.
Another easy thing to check is your computer pin 46 ground. Pin 46 is a dedicated ground for a lot of your sensors, and routes through your computer. This sometimes get burned out on the inside of the computer and can cause all sorts of issues. To check it locate the pin 46 wire on the diagnostics connector (the link Jrichker posted about pulling codes shows the connector and the correct pin) use a DVM set ohms to check resistance between that pin and ground on the car or negative battery post. You should have no more that 1 ohm of resistance. Any more and it's likely the trace on the computer is damaged.
Another easy thing to check is your computer pin 46 ground. Pin 46 is a dedicated ground for a lot of your sensors, and routes through your computer. This sometimes get burned out on the inside of the computer and can cause all sorts of issues. To check it locate the pin 46 wire on the diagnostics connector (the link Jrichker posted about pulling codes shows the connector and the correct pin) use a DVM set ohms to check resistance between that pin and ground on the car or negative battery post. You should have no more that 1 ohm of resistance. Any more and it's likely the trace on the computer is damaged.
About to start check the wires. Does anyone know why my mustang is missing the 10pin connectors? (Salt & Pepper shakers)Similar threads
