20 Most Recent 1986 Ford Mustang Questions & Answers

Mass air flow or computer.

The relay buzzing is a common symptom for a low battery. I'd suggest you check the charge of your battery and, assuming it's low, charge it then perform a load test. It's possible a low battery could be the cause for the engine failing to start, even when the engine was spinning from the starter. But if you find it still will not start even with a good battery, then you'll need to confirm if you are getting spark and fuel. "Did not fire" could be interpreted to mean there was no spark, but I suspect you just meant it did not start. Is that due to lack of spark or lack of sufficient fuel pressure. To do much further diagnosis you'll need a charged battery and to provide a bit more detail.

hi thats all goood and that but the 3 engines your talking about have all got difrent head sizers and youl have to change you hole manafold and other things to but its a easy job thanks ben

There should be a fuel inertia switch that you press once to reset it. On my 1987 Ford Mustang GT it was located in the Rear Hatch area by my drivers side taillight. I had to remove the plastic to access it. look there first on most of the ford cars from the 1980's the switch was always in the hatchback area or truck. Some cars had easy access to the switch others where hidden. After you reset switch turn key to the power ON key position not turned over just one turn of your key ahead you should hear the pump prime....now do this 5-6 six more times this will build pressure in the hp fuel line. Turn hear over. Hope this helps you. Here's a few pic's of the switch's for your reference's mine had the white top the red top switch's came out in 89 or 90 model year fords if I remember correctly.

Check Fuel Pump Relay--(under drivers seat) Check reset on inertia switch (in trunk left of wheel well)

Here is how to detect a drain in system! Use a test light, Hook up test light to the negative terminal on battery. ( unhook terminal first.) connect opposite end of test light to negative on battery. If a drain, light will be on. Start pulling fuses from fuse box. when the test light goes out, that is the problem curcuit. let sit 3to5 minutes before pulling fuses. Good-Day!

Engine stalls cold or RPM fluctuates at idle up and down or dies near idle.

This problem is commonly caused by a dirty automatic idle speed control valve and throttle valve but always run a OBD2 fault code as well as the cleaning procedure. Buy a can of throttle valve cleaner (do not use carburetor spray cleaner!) from NAPA or Carquest (made by CRC chemicals) and spray it into the air intake while the engine is running, use up about 1/2 the can, engine will try to stall hold the speed up, shut it down and let it soak for 30 minutes, restart and blow out the remaining fluid, shut it down and disconnect the negative battery cable for 5 Min's to reset the base idle control. If the above cleaning doesn't cure your issues you need to have the computer controlled automatic idle speed control system diagnosed and repaired by a dealer or electronic engine control repair shop.

check HT leads firing order as you will probably have 2 wires crossed. ensure that the HT leads do not touch each other. Have a compression test done to check for valve problem

It may be just plain worn out (341k wow) you couldn't blame it could you

check the spark from the plug wires. if it has sprark then its a fuel problem

I WOULD CHECK FUEL PUMP, GAS FILTER, FUEL PRESSURE REGULATOR.

do you have spark at spark plugs, have you checked fuel pressure, could spray some carb. cleaner in intake and see if it will run then on carb cleaner but be carefull, if engine backfires could catch on fire so be prepared.

check fuses connectors or bad earthing.