Spark problems

[wht87gt]

Ok so heres the deal, I'm having a missfire issue and I've been trying to track it down for the past few days. Today I ran a cylinder balance test and found that cylinders 2 and 3 are bad. So I hook up my noid lights to those injectors and they are firing OK. So then I test for spark at the distributor for those two cylinders and got nothing at all. Now, I do have good spark from the coil to the distributor and also have good spark to all other cylinders. Cap and rotor are fairly new, distributor is a few years old, coil is original and the tfi is brand new. I'm kinda stumped on this one, I don't understand how I'm not getting spark on two out of eight cylinders. I may be wrong but if the rotor is giving spark to one cylinder shouldn't it give spark to all of them? Sorry this was so long and I hope I worded it clearly enough. I would really appreciate any help you guys can pass on.

 

[HISSIN50]

Swap the plug wires on those two bad cylinders with two good ones and see if the misfire follows the wires.

 

[wht87gt]

Hissin, thanks for the reply. Could bad plug wires cause me to not get spark at the distributor cap on just those two cylinders? My spark tester shows spark at all distributor cap terminals except cylinders 2 and 3.

 

[HISSIN50]

If there is no spark leaving the cap itself for those two cylinders, swap on a spare cap (if you have one).
If you don't, inspect the inside of the cap for cracks. I've had 'em crack before and it created a nasty misfire.

 

[wht87gt]

Ok a little update, I tried a brand new cap and rotor this morning and nothing changed. If you look at the terminals under the cap you can actually see that cylinders 2 and 3 are not getting any spark. All the other terminals have marks on them from the spark. I also swapped a known good plug wire onto the number 2 cylinder and nothing changed. Could the pick up in the distributor be the problem? The distributor is a reman from autozone so I can always just get a new one on the lifetime warranty. Anyone have anymore suggestions? I'm really at a loss on this one.

 

[jrichker]

Ok a little update, I tried a brand new cap and rotor this morning and nothing changed. If you look at the terminals under the cap you can actually see that cylinders 2 and 3 are not getting any spark. All the other terminals have marks on them from the spark. I also swapped a known good plug wire onto the number 2 cylinder and nothing changed. Could the pick up in the distributor be the problem? The distributor is a reman from autozone so I can always just get a new one on the lifetime warranty. Anyone have anymore suggestions? I'm really at a loss on this one.

The shutter wheel in the bottom of the distributor could be bent or damaged.

Dump the codes and look for code 14, which indicates PIP circuit problems.

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 http://www.troublecodes.net/Ford/

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.

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

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

Alternate methods:
For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see http://www.midwayautosupply.com/pc-7208-90-equus-digital-ford-code-reader-3145.aspx – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

 

[montegoman351]

So, how do the plugs look ok? The spark has to have ground to travel to the plug gap...(I.E. ground electrode) Also, make sure they're Motorcraft plugs...IDK, I've seen problems out of the "on sale" auto parts store plugs... Since you have swapped the wires around...and had no change, check the plugs, and pull the codes as stated above. Oh, you can swap the plugs to a functioning cylinder, and see if the miss follows.

 

[wht87gt]

Thanks guys, I have pulled the codes and didn't get a code 14 for the pip signal, I did get a 33, 44, 21, and 94. None of which I believe apply to my current issue. I will be taking care of those codes once I figure this problem out. But back to the current issue, I did pull some of the plugs and they do look pretty black. The car is running very rich maybe due to my code 21? (bad ECT)? So maybe the plugs are too fouled to fire? I'll have to switch the plugs around and see if the problem follows. Thanks again guys! I appreciate the help.

 

[jrichker]

Code 21 – ECT sensor out of range. Broken or damaged wiring, bad ECT sensor.
Note that that if the outside air temp is below 50 degrees F that the test for the
ECT can be in error.

The ECT sensor has absolutely nothing to do with the temperature gauge. They are
different animals. The ECT sensor is normally located it the RH front of the engine in
the water feed tubes for the heater.

The ACT & ECT have the same thermistor, so the table values are the same

ACT & ECT test data:

Use Pin 46 on the computer for ground for both ECT & ACT to get most accurate
readings.

Pin 7 on the computer - ECT signal in. at 176 degrees F it should be .80 volts

Pin 25 on the computer - ACT signal in. at 50 degrees F it should be 3.5 volts. It is
a good number if the ACT is mounted in the inlet airbox. If it is mounted in the lower
intake manifold, the voltage readings will be lower because of the heat transfer.

Voltages may be measured across the ECT/ACT by probing the connector from
the rear. A pair of safety pins may be helpful in doing this. Use care in doing it
so that you don't damage the wiring or connector.

Here's the table :

50 degrees F = 3.52 v
68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61
212 degrees F = .47 v
230 degrees F = .36 v
248 degrees F = .28 v

Ohms measures at the computer with the computer disconnected, or at the sensor with the sensor disconnected.

50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms
212 degrees F = 2.07 K ohms
230 degrees F = 1.55 K ohms
248 degrees F = 1.18 k ohms

Diagram courtesy of Tmoss & Stang&2birds

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds
(website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

Code 33 - Insufficient EGR flow detected.
Look for vacuum leaks, cracked vacuum lines, failed EGR vacuum regulator. Check to see if you have 10” of vacuum at the EGR vacuum connection coming from the intake manifold. Look for electrical signal at the vacuum regulator solenoid valves located on the rear of the passenger side wheel well. Using a test light across the electrical connector, it should flicker as the electrical signal flickers. Remember that the computer does not source any power, but provides the ground necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side will go to ground or below 1 volt as the computer switches on that circuit.
Check for resistance between the brown/lt green wire on the EGR sensor and pin 27 on the computer: you should have less than 1.5 ohm.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif


EGR test procedure courtesy of cjones

to check the EGR valve:
bring the engine to normal temp.
connect a vacuum pump to the EGR Valve
apply 5in vacuum to the valve.
if engine stumbled or died then EGR Valve and passage(there is a passageway through the heads and intake) are good.
if engine did NOT stumble or die then either the EGR Valve is bad and/or the passage is blocked.
if engine stumbled, connect vacuum gauge to the hose coming off of the EGR Valve
snap throttle to 2500 RPM (remember snap the throttle don't hold it there).
did the vacuum gauge show about 2-5 in vacuum?

if not, check for manifold vacuum at the EGR vacuum valve.
if you have manifold vacuum then connect vacuum gauge to the EGR valve side of the vacuum valve and snap throttle to 2500 RPM.
should read about 2- 5 in vacuum

The operation of the EGR vacuum regulator can be checked by using a test light applied across the wiring connector. Jumper the computer into self test mode and turn the key on but do not start the engine. You will hear all the actuators (including the EVR vacuum regulator) cycle. Watch for the light to flicker: that means the computer has signaled the EGR vacuum regulator successfully.


Codes 44 & 94 - AIR system inoperative - Air Injection. Check vacuum lines for leaks, & cracks. Disconnect the big hose from smog pump: with the engine running you should feel air output. Reconnect the smog pump hose & apply vacuum to the first vacuum controlled valve: Its purpose is to either dump the pump's output to the atmosphere or pass it to the next valve. The next vacuum controlled valve directs the air to either the cylinder heads when the engine is cold or to the catalytic converter when the engine is warm. Disconnect the big hoses from the back side of the vacuum controlled valve and start the engine. Apply vacuum to the valve and see if the airflow changes from one hose to the next.
The two electrical controlled vacuum valves mounted on the rear of the passenger side wheelwell turn the vacuum on & off under computer control. Check to see that both valves have +12 volts on the red wire. Then ground the white/red wire and the first solenoid should open and pass vacuum. Do the same thing to the light green/black wire on the second solenoid and it should open and pass vacuum.

Remember that the computer does not source power for any actuator or relay, but provides the ground necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side will go to ground or below 1 volt as the computer switches on that circuit.

The computer provides the ground to complete the circuit to power the solenoid valve that turns the vacuum on or off. The computer is located under the passenger side kick panel. Remove the kick panel & the cover over the computer wiring connector pins. Check Pin 38 Solenoid valve #1 that provides vacuum to the first Thermactor control valve for a switch from 12-14 volts to 1 volt or less. Do the same with pin 32 solenoid valve #2 that provides vacuum to the second Thermactor control valve. Starting the engine with the computer jumpered to self test mode will cause all the actuators to toggle on and off. If after doing this and you see no switching of the voltage on and off, you can start testing the wiring for shorts to ground and broken wiring. An Ohm check to ground with the computer connector disconnected & the solenoid valves disconnected should show open circuit between the pin 32 and ground and again on pin 38 and ground. In like manner, there should be less than 1 ohm between pin 32 and solenoid valve #2 and pin 38 & Solenoid valve #1.

If after checking the resistance of the wiring & you are sure that there are no wiring faults, start looking at the solenoid valves. If you disconnect them, you can jumper power & ground to them to verify operation. Power & ground supplied should turn on the vacuum flow, remove either one and the vacuum should stop flowing.
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

See http://forums.stangnet.com/attachment.php?attachmentid=50636&d=1180923382 for a very nice drawing of the Thermactor Air System (smog pump) plumbing

If you have a catalytic converter H pipe, you need to fix these codes. If you don't, then don't worry about them

 

[wht87gt]

Spark Problems - Update

So, I've tried everything that you guys suggested to me and I am still having my spark problems. Up to now I've checked the resistance on my wires and they are OK, tried new plugs, cap and rotor, borrowed a known good coil, and nothing has helped. I still don't get any spark at cylinders wires 2 and 3 on the distributor cap. But what I noticed today is if I hook up my spark tester to one of those terminals on the cap I can get spark if I rev the engine. Once I let it idle the spark goes away. So the only thing I can think of at this point is the pickup in the distributor might be bad. The distributor I have in there now is from Autozone so I ordered a new one under the lifetime warranty for free. I figure it can't hurt to swap in a new distributor since it's free. So you guys have anyother ideas for me? I don't know what to do next if the distributor doesn't fix my problem. Thanks.

 

[wht87gt]

So I swapped out the old distributor for a new one and it seemed to fix my spark issues. I'm getting spark on those two cylinders now and the miss seems to be gone. I haven't had a chance to actually drive it so we'll see how that goes. Thanks to everyone that helped out.