NEED HELP!!!! Engine just developed bad Misfire!!!

[Katmandu]

This is VERY urgent since I'm selling the car tomorrow!!

91 GT 5.0. NO KNOWN problems (until and hour ago). Car "was" running GREAT before I did this.....

I was going over the car fixing little details to prepare it to be sold TOMORROW. Buyer is driving (8) hours to come pick it up.

I went to the car wash to wash her down and get the some dust/dirt off her. I lightly washed over the engine being CAREFUL NOT to spray down the ignition/coil/wires/distributor.

After I was done, it fired up right away and continued to run GREAT as usual.

I drove about (1) mile home and parked it.

Popped the hood to dry off the engine/chrome by hand and I noticed the top radiator hose was sucked closed. I thought that was odd and proceed to check the radiator/coolant/overflow tank.

The overflow tank was filled to full and the coolant looked OK.

I took the radiator cap off and found the coolant to be brown. I've driven the car very little this season (maybe 2,000 miles or so) and it's sat in my garage the rest of the time. The coolant was NOT that dirty that last time I checked it a few months ago.

So, I proceeded to flush the radiator and engine. I was fairly dirty and did (3-4) complete flushings using straight water from the hose. I was very careful NOT to run it more than 3-4 minutes at a time to allow the thermostat to open and flush out the block/heater core. The Temperature gauge never went about the mid-way point the whole time.

On the last flushing I noticed the engine start to idle a bit rough. Nothing drastic, just not smooth as usual.

I finished filling it with a gallon of Coolant and the rest water. I believe 5.0s actually take (2) gallons of Coolant. Knowing this, I jumped in the car and headed towards the parts store (a mile away).

I got about (2) blocks from my house and the engine started misfiring BAD. I immediately turned back towards my house and the engine stalled out. I went to fire it back up and the engine/started just spun and then STOPPED. I immediately turned the key again and the SAME thing happened. Engine/started spun as Normal and the STOPPED.

I don't believe this is heat related and/or due to the radiator/engine flushing since the engine spins freely whenever I return the key.

There is NO smoke out the exhaust and NO oil indicated in the radiator. So I believe the head gaskets are still OK.

The only ignition related issue I know of is a bad wire connection to the coil. The coil wire (from the coil -->distributor) has a bad connection under the boot. I accidently damaged it along time ago removing it off the coil. I forgot about fixing it since I was able to get it connected when I put the boot back on. I'm going to go out and try to fix it properly right now.

What the heck is going on with this thing ?????? Would that bad coil wire be giving me all this grief ???

I need help NOW!!


TIA!

ERIC

 

[jrichker]

Steam will often collect in the distributor cap when you mess with the cooling
system on a warm or hot engine. When the distributor cap cools down, the
water vapor will condense inside the cap and on the wiring. The fix is to remove
the cap, wipe it out and spray the inside of the cap and spark plug wires with WD40.

If that does not fix it, do a cylinder balance test to isolate the bad cylinder(s)

Cylinder balance test:
Warm the car's engine up to normal operating temperature. Use a
jumper wire or paper clip to put the computer into test mode. Start
the engine and let it go through the normal diagnostic tests, then
quickly press the throttle to the floor. The engine RPM should exceed
2500 RPM's for a brief second. The engine RPM's will increase to about
1450-1600 RPM and hold steady. The engine will shut off power to each
injector, one at a time. When it has sequenced through all 8 injectors,
it will flash 9 for everything OK, or the number of the failing cylinder
such as 2 for cylinder #2. Quickly pressing the throttle again up to
2500 RPM’s will cause the test to re-run with smaller qualifying figures.
Do it a third time, and if the same cylinder shows up, the cylinder is
weak and isn’t putting out power like it should. See the Chilton’s Shop
manual for the complete test procedure

Dump the codes and see what the computer says is wrong…Codes may be present in the computer
even if the Check Engine light isn’t on.

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check
engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing
test lamp or Check Engine Light and count the flashes.

See Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical

If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no
functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

The STI has a gray connector shell and a white/red wire. It comes from the same
bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

The STI has a gray connector shell and a white/red wire. It comes from the same
bundle of wires as the self test connector.

Do not jumper anything to the single dark brown connector. It is the power for the
under the hood light. It is in another bundle of wires near the windshield wiper.

Do a compression test on all the cylinders.
Take special note of any cylinder that shows up as weak in the cylinder
balance test. Low compression on one of these cylinders rules out the
injectors as being the most likely cause of the problem. Look at cylinders
that fail the cylinder balance test but have good compression. These
cylinders either have a bad injector, bad spark plug or spark plug wire.
Move the wire and then the spark plug to another cylinder and run the
cylinder balance test again. If it follows the moved wire or spark plug,
you have found the problem. If the same cylinder fails the test again,
the injector is bad. If different cylinders fail the cylinder balance test,
you have ignition problems or wiring problems in the 10 pin black &
white electrical connectors located by the EGR.

How to do a compression test:
Only use a compression tester with a screw in adapter for the spark
plug hole. The other type leaks too much to get an accurate reading.
Your local auto parts store may have a compression tester to rent.
If you do mechanic work on your own car on a regular basis, it would
be a good tool to add to your collection.

With the engine warmed up, remove all spark plugs and prop the
throttle wide open, crank the engine until it the gage reading stops
increasing. On a cold engine, it will be hard to tell what's good &
what's not. Some of the recent posts have numbers ranging from
140-170 psi. If the compression is low, squirt some oil in the cylinder
and do it again – if it comes up, the rings are worn. There should be
no more than 10% difference between cylinders. Use a blow down
leak test (puts compressed air inside cylinders) on cylinders that
have more than 10% difference.

See the link to my site for details on how to build your own blow
down type compression tester.

 

[DrMaxit]

Good post, will this work for SD cars as well? bc I want to do a power balance test on mine.
Also is the IAC needed to be present for the test to rev the motor up? or does it change the maps do do this? Ugh.. my car needs a lot of stuff.

--Chuck

 

[Katmandu]

Found the problem and was ignition related.

The wire to the (+) side of the coil came loose from it's connector. I probably bumped it when I was drying off stuff under the hood.

Gave me a friggin heart attack!!! I was thinking the worst. Blown head gasket, cracked heads, seized engine and worst of all NO SALE tomorrow!

Thank goodness it was something simple and thank god for BEER afterwards!!

 

[jrichker]

Good post, will this work for SD cars as well? bc I want to do a power balance test on mine.
Also is the IAC needed to be present for the test to rev the motor up? or does it change the maps do do this? Ugh.. my car needs a lot of stuff.

--Chuck

The test works for all 5.0 Mustangs from 86-95.
The IAC is used to control engine speed for these tests. It must be present and working correctly to do the test.