87 5.0 starting/idling problem

Welcome to the boards.

The battery cables have probably seen better days. I might just replace them and add an extra motor ground to have a known good platform.

Pull the codes if you can. If it sat for a bit, the IAC might be an issue. Cleaning it can help but I never clean them unless I'm prepared to replace them. Otherwise, getting it to run and letting it idle a bit might clean up varnished injectors, a sticky IAC, etc.

Good luck and nice pick-up.

IAC Idle Air Controlloer also known as IAB, Idle Air Bypass.

See the "Surging Idle Checklist for help with all your idle/stall problems. Everything you need to find and fix idle problems is in there.

The first two posts contain all the updates to the fixes. At last count there were 24 possible causes and fixes for surging idle/stall problems. I continue to update it as more people post fixes or ask questions.

tc3k101 said:

****************************UPDATE*******************

ok i just got done replacing the solonoid, nothing, jacked the car up. hit the hell out of the starter, nothing.

started checking everything out find this clip is broken and doesnt stay latched. tape it on car doesnt want to turn over but i pop start it and it idles!
but i do need to replace this harness but i have no idea what the part is called or how to go about replacing it :/ nd ideas?

i realize it isnt safe but the car is going no where until we are done. i plan on replacing the starter tomorow if it doesnt rain.

Click to expand...

That is the IAC (or IAB if you prefer).

No Crank checklist for 5.0 Mustangs

Revised 30-Jan-2009 to reorder checklist and add cleaning procedure for connections.

Since some of the tests will bypass the safety interlocks, make sure that the car is in neutral and the parking brake is set. Becoming a pancake isn’t part of the repair process…

1.) Will the car start if it is jumped? Then clean battery terminals and check battery.
The battery posts and inside of the battery post terminals should be scraped clean with a knife or cleaner brush tool.

The clamp on with 2 bolts battery terminal ends are a know problem causer. Anyplace you see green on a copper wire is corrosion. Corrosion gets in the clamped joint and works its way up the wire under the insulation. Avoid them like the plague...

A voltmeter is handy if you are familiar with how to use it to find bad connections. Measure the voltage drop across a connection while trying to start the car: more than .5 volts across a connection indicates a problem.

See http://www.fluke.com/application_notes/automotive/circuit.asp?AGID=1&SID=103 for help for help troubleshooting voltage drops across connections and components. .



2.) Check the battery to engine block ground down near the oil filter, and the ground behind the engine to the firewall. All grounds should be clean and shiny. Use some sandpaper to clean then up.

3.) Jump the big terminals on the starter relay next to the battery with a screwdriver - watch out for the sparks! If the engine cranks, the starter and power wiring is good. The starter relay is also known as a starter solenoid.

4.) Then pull the small push on connector (small red/blue wire) off the starter solenoid (Looks like it is stuck on a screw). Then jump between the screw and the terminal that is connected to the battery. If it cranks, the relay is good and your problem is in the rest of the circuit.

5.) Remember to check the ignition switch, neutral safety switch on auto trans and the clutch safety switch on manual trans cars. If they are good, then you have wiring problems.

Typical start circuit...
Diagram courtesy of Tmoss & Stang&2birds



6.) Pull the starter and take it to AutoZone or Pep Boys and have them test it. Starter fails test, then replace it. If you got this far, the starter is probably bad.

AutoZone wiring diagrams

For 79-88 model Mustangs
http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c1528004e28c

For 89-93 model Mustangs
http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c15280069677

For 94-98 model Mustangs
http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c152801f5e3b

For 1999-2005 model Mustangs
http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c152801ef7d7


Starter solenoid wiring for 86-91 Mustang



Starter solenoid wiring 92-93 Mustang or earlier Mustang with upgraded high torque mini starter.