Bad Codes

[Blown88GT]

1. Bad O2 sensor will set codes 4/191 or 42/92.
2. Try putting some window screen in front of the MAF to see if there are any turbulence problems in the air intake. The stock 55MM MAF had one.

I'm sorry, maybe I wasn't clear.
1. No codes are being set. Can a sensor be bad without setting codes? BTW, it's 41 & 42 (your typo).
2. Speed Density doesn't have inputs for MAF. Installed meter is 76mm when new A9L replaces SD EEC. MAF harness is not even plugged in. The stock MAF's all have screens, the C&L doesn't need one, only 6 in of straight flow before it.

 

[jrichker]

Bad O2 sensor usually set codes.

Here's the check procedure to find out:

Code 41 or 91 Three digit code 172 or 176 - O2 sensor indicates system lean. Look for a vacuum leak or failing O2 sensor.

Revised 22-Jun-2009 to include 3 digit code and wiring for 94-95 5.0 Mustangs

Code 41 is a RH side sensor,
Code 91 is the LH side sensor.

Code 172 is the RH side sensor
Code 176 is the LH side sensor

The computer sees a lean mixture signal coming from the O2 sensors and tries to compensate by adding more fuel. Many times the end result is an engine that runs pig rich and stinks of unburned fuel.

The following is a Quote from Charles O. Probst, Ford fuel Injection & Electronic Engine control:
"When the mixture is lean, the exhaust gas has oxygen, about the same amount as the ambient air. So the sensor will generate less than 400 Millivolts. Remember lean = less voltage.

When the mixture is rich, there's less oxygen in the exhaust than in the ambient air , so voltage is generated between the two sides of the tip. The voltage is greater than 600 millivolts. Remember rich = more voltage.

Here's a tip: the newer the sensor, the more the voltage changes, swinging from as low as 0.1 volt to as much as 0.9 volt. As an oxygen sensor ages, the voltage changes get smaller and slower - the voltage change lags behind the change in exhaust gas oxygen.

Because the oxygen sensor generates its own voltage, never apply voltage and never measure resistance of the sensor circuit. To measure voltage signals, use an analog voltmeter with a high input impedance, at least 10 megohms. Remember, a digital voltmeter will average a changing voltage." End Quote

Testing the O2 sensors 87-93 5.0 Mustangs
Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear. The computer pins are 29 (LH O2 with a dark green/pink wire) and 43 (RH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.


Testing the O2 sensors 94-95 5.0 Mustangs
Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear. The computer pins are 29 (LH O2 with a red/black wire) and 27 (RH O2 with a gray/lt blue wire). Use pin 32 (gray/red wire) to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.


Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter. Do not attempt to measure the resistance of the O2 sensors, it may damage them.

Testing the O2 sensor wiring harness
Most of the common multimeters have a resistance scale. Be sure the O2 sensors are disconnected and measure the resistance from the O2 sensor body harness to the pins on the computer.

The O2 sensor ground (orange wire with a ring terminal on it) is in the wiring harness for the fuel injection wiring. I grounded mine to one of the intake manifold bolts

Make sure you have the proper 3 wire O2 sensors. Only the 4 cylinder cars used a 4 wire sensor, which is not compatible with the V8 wiring harness.

Replace the O2 sensors in pairs if replacement is indicated. If one is weak or bad, the other one probably isn't far behind.

If you get only code 41 and have changed the sensor, look for vacuum leaks. This is especially true if you are having idle problems. The small plastic tubing is very brittle after many years of the heating it receives. Replace the tubing and check the PVC and the hoses connected to it.
A secondary problem with only a code 41 is for cars with an intact smog pump and cats. If the tube on the back of the heads clogs up the driver’s side, all the air from the smog pump gets dumped into one side. This excess air upsets the O2 sensor calibration and can set a false code 41. The cure is to remove the crossover tube and thoroughly clean the insides so that there is no carbon blocking the free flow of air to both heads.

 

[Blown88GT]

Thanks for your response.

I have the Innova Electronics code reader & code book.
Also have the Probst book.
Also have a Fluke 87-V, with analog scale.

3-digit codes didn't start until 1991. 41 & 91 have the same definition in the code book.

Went back to basics today:
1. Set fuel pressure to 39psi, vacuum line removed & plugged
2. Verified firing order 1-3-7-2-6-5-4-8; & #1 to distr cap.
3. With spout removed, checked base timing at 10 degBTDC.
4. Ran timing procedure while in test mode KOER to verify 20deg above base timing.
5. Removed EGR valve to inspect & clean.
6. Removed Crane HI-6 ignition, now back to stock except for PS-91 coil.
7. Tested TPS according to procedure in Probst.
8. Tested TFI according to procedure in Probst.
9. Vacuum lines from B/R to FMU & surge valve (removed from inlet) from tree which is now capped at B/R. FMU doesn't close off fuel return until pressure is applied to vacuum port. It's open to atmosphere so fuel just flows through it.

Road tested 3 times, same result. Pretty much dies when accelerator is depressed & vacuum drops. Lots of popping in exhaust.

10. Ran the O2 test at idle. EEC was already on the floor with the with the wire cover removed. Also have a spare connector from the JY to snoop before going to the real one. Voltage swings all over from below .1 to .9, According to analog scale, it swings from min. to max. to min., etc. Voltage seems to rise to these values after closed loop.

Only thing left is a vacuum leak but issue only occurs when vacuum is lower, otherwise steady at 20 inHg. until under load & vacuum drops.

Maybe a bad hose under or on the back of the upper intake? Maybe one of the hard lines which is covered with the rubber caps?

 

[jrichker]

You either have a crossfire from spark leaking in the wiring, or cap or a leaking injector. A spray bottle of water and a dark place to run the engine while you spray the wires with the spary bottle may reveal spark jumping around. Remove the distributor cap and look for carbon tracks on the rotor side and the wire side.

The leaking injectors are harder to spot unless they leak so bad that they carbon up the spark plugs.

Since you have the proper tools, check the ACT & ECT sensors to make sure that they are in range.

Dumping the codes will normally show a faulty sensor. The ACT & ECT may be on the outer limits and not set a code but cause problems. Use a DVM or multimeter to check them.

Pin 25 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.

Pin 7 ECT signal in. at 176 degrees F it should be .80 volts

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

Here's the table: The values are +/- 15%, so don't get worried if your readings vary a little bit.

Voltages are measured across the two connector pins of the sensor with the sensor connected. Some safety pins used to probe the connector from the rear will be helpful

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 wiring 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

 

[HISSIN50]

I have only skimmed the thread so if I'm off target, please disregard the reply:

If checking particular wires for possible induction issues, this might help note wires to check:

http://351winsor.com/joel/EEC-IV/SparkWires_Routing.JPG?SSImageQuality=Full

 

[Blown88GT]

Thanks to jrichker & HISSIN50
Any & all suggestions are welcome. I'm running out of the "easy" stuff.
I actually ohmmed out ACT or ECT, several weeks ago before this all got out of control & they were right on according to the table. I'll go back to address it again.

If I had realized this was going to be a Science Project, I would have kept detailed notes.

The firing order & routing haven't been haven't been touched in years. Firing order from Ford is suspect. Several of my '88 Ford books are wrong. The pic on the distributor doesn't match the firing order shown below.

Big Blue Ford Manual says:
Distributor Pic shows - 1,3,7,2,6,5,4,8
Below pic says:
5.8L - 1,3,7,2,6,5,4,8
5.0L - 1,5,4,2,6,3,7,8
The link that HISSIN50 provided shows:
5.0 HO Firing order:
1,3,7,2,6,5,4,8
...I wonder what it's really supposed to be?
Internet searches generally say 5.0HO & 5.8 are both the same: 1,3,7,2,6,5,4,8
My wire routing looks exactly like the pics.
This would confirm it's been correct all along: http://www.302w.com/Firing-Order.aspx

I am having trouble identifying physical locations of ACT & ECT.
My manuals don't agree where they are & what they look like. P.37 & 38 differ.

ECT has 1 wire according to p.38, p.37 is hard to tell, but look like 1-wire. All drawings show 2 wires & a 2-wire connector.
On the car, I can see a 1-wire something on the top of the lower intake & a 2-wire something (ACT) behind it.

ECT = 9.45K ohms at pin-7 on EEC w/EEC connected
ACT = 9.71K ohms at pin-25 on EEC w/EEC connected

ECU ACT & ECT are likely NPN open collectors with sensor completing circuit from emitter to ground.
For TAB & TAD, NPN open collector with coil of actuator completing circuit from collector to Vcc.
This is all Old School driver circuits, that's how I would have done it in the 80's with discrete components.
It's not Rocket Science & I was a Rocket Scientist. (LOL)

I'm really leaning towards a difficult to find vacuum leak. Need to find a vacuum leak smoke detector.

 

[HISSIN50]

On page 38, the thing labeled as the ECT sensor should be labeled as the gauge's sending unit. It has just one wire and is on the driver's side lower intake. As you know, this is only for the gauge.

The ACT is further back (near #5 runner), with multiple wires.

The ECT is on the heater tube on the passenger side. It's got multiple wires.

If your readings were off from what you expected [given the ambient and operating temps], I'd disco' the leads to the sensors (ACT and ECT) and Ohm out each one.

For a more complete test, check the voltage of the thermistors (so you take into account both wires in each sensor's circuit)

 

[jrichker]

This doesn’t prove that the block is a HO block. Some trucks evidently use a HO firing order
with a low lift cam. However, it will definitely prove that a block can’t be HO because the firing order is wrong.

Remove the #1 & #3 spark plugs. Put your finger in #1 spark plug hole. Crank the engine over until you feel compression on #1 cylinder. Slowly turn the engine until the TDC mark and the timing pointer line up. Mark TDC on the balancer with chalk or paint. Put your finger in #3 spark plug hole and crank the engine 90 degrees. You should feel pressure trying to blow past your finger. If you do not feel pressure, repeat the process again. If you feel pressure, it is a HO engine.

No pressure the second time, remove spark plug #5. Put your finger in #1 spark plug hole. Crank the engine over until you feel compression on #1 cylinder. Put your finger in #5 spark plug hole and crank the engine 90 degrees. If you feel pressure now, the engine is not a HO model, no matter what it says on the engine.

Using a small carpenter or machinist square to mark the harmonic balancer off into 90 degree sections may be helpful here.

A 15/16 deep socket & breaker bar or ratchet may be used to turn the engine.

The HO firing order is 1-3-7-2-6-5-4-8.
Non HO firing order is 1-5-4-2-6-3-7-8

 

[Blown88GT]

Thanks a lot. Don't remember your name but probably shouldn't be using names in an open forum. Corral is of little help in these matters, I've had 0 responses to my post on the same issue. You didn't think I would bring you guys an easy problem?

Car was parked after I lost my job & had other personal matters to deal with. It was already beginning to develop issues & I had no time or inclination to deal with them. Almost sold it, put a few ads out there but no response. Can't really do this work in the summertime, just too hot in South Florida & we had the hottest summer on record, it was 98 every day, when usually 90 is normal. At least no hurricanes.

I forgot about the gauge sensor. Readings were where they should be with current ambient temp & engine off for a few hours.

This Science Project is frying my brain. Since the EEC is lying on the passenger side floor, it was the easiest to access from my 2-car garage with the car in the middle. Driver's door opens most of the way, passenger all the way. Front of vehicle is at the workbench & toolboxes. It's a small 2-car garage, not much wider than the door itself. Better than the old place where I had no garage.

I kept all the original parts except the suspension pieces, just too heavy & took up far too much space. About 4 Rubbermaid containers now located in the garage next to the usual car spot. Car usually gets backed in so I can open the door. Truck goes in forward so I can open the door.

Did some "refined word" Google searching & found a Mustang with the same symptoms. After chasing fuel & everything else & replacing parts all over, he replaced the defective Accel coil with an MSD. Accel coil was only delivering 25k volts. When I go to AutoZone, I'll see if they can test the PS91.

I had the original Ford ignition coil, so I installed it late last night in place of the Crane PS91 coil. I had also forgotten how difficult it was to remove the factory bracket for the coil. I had no room for the chromed PS-91 housing. The PS-91 was for the Crane HI-6 ignition which has been disconnected for this Project.

I didn't mention it before because it wasn't necessarily relevant, had to replace the battery a couple days ago. The failure mode was a strange one. It would start once or twice, then "click-click". Only 2 minutes on a 6A charger was enough to crank & start. A couple years ago it spewed white crud from the + terminal which I thought was strange.

It had been on a battery maintainer it's entire life. Lasted 67 mo. out of 100 mo. Sears Gold warranty. No Gold replacement anymore, got Silver instead, but it actually is rated at more CCA.

Anyway, weather may not allow for road testing today & I need a break. I'm busier in retirement than when I was working.

UPDATE:
It's not the coil.
I'l try to describe symptoms more accurately.
Issue happens engine warm or cold.
Depress accelerator, surges forward, power cuts off, comes on, surges forward, goes off, comes on, cycles about every second, almost like someone is throwing a switch on & off repeatedly. Afraid to continue because exhaust starts popping & car is jerking forward & back. Let off gas & cruise into garage. If it was carb, I'd say accelerator pump.

I would swear it's the firing order, but it's correct for 302HO.
Can injectors stick only under load?
The only difference under load is vacuum.

Pulled #5 plug because it's easiest to get to. A lot of carbon on the insulator, but I'm not surprised because of the over rich condition.
The car ran fine for over 15 years.

 

[Blown88GT]

New Question:
Can a code scan (KOER) be obtained while performing a road test?
No codes shown in CM (continuous memory).
Manuals only talk about idleing. Or is that what the CM is for?

 

[HISSIN50]

Trying to pull codes while the vehicle was rolling would be a little scary. If the issue is able to trigger a code during a previous drive session, it should be recorded and be retrieved while pulling codes.

If the issue is not something that triggers a code, then it gets tougher (something like a leaking plug wire - the EEC probably will not note a code but the car obviously will run like crap)

Only 94+ Mustangs can display PIDs (real time data while idling or driving).

If you self-tune, you could try to datalog a session.

 

[jrichker]

The only thing left is the PIP sensor in the distributor or it is leaking spark from one spark plug wire to another spark plug wire.

 

[Blown88GT]

Already on it: PIP or TFI.
There is no more testing to be done.

Thought I could install only the PIP, but not on my distributor. The top "breaker plate" is not removable even though the one I got from the salvage yard with exactly the same part number is removable. I bent mine up trying to get it off. The JY one has a lot more wear, but could have been rebuilt without removing it from the engine.

Drove out the roll pin for the gear but it's not coming off without a press. There's another "carrier bearing" above which also has a roll pin, same as the JY one. There's a top bushing below the breaker plate, which is supposed to come off the top.

There are some decent pics here from a '94 Cobra, not exactly the same, but close: How to disassemble your distributor! - MustangForums.com

Autozone's repair guide is 100% correct regarding what is replaceable.| Repair Guides | Distributor Ignition | Eec-iv/tfi-iv Electronic Engine Control | AutoZone.com

I can get a rebuilt distributor for $60 (with core & I have 2 cores), the PIP alone was $20.

I'm only installing 1 part at a time on it because I want to know who the guilty party is. I'm now commited to the PIP, because I don't have a working distributor. This is the first time I've ever pulled a distributor, but put the engine at TDC, marked the distr base, body, etc. I'll have my old one to line up the new one.

 

[HISSIN50]

Blown88GT, check your PM's

 

[jrichker]

Putting the distributor back in and setting the timing.

Putting the distributor back in is fairly simple. Pull #1 sparkplug, put your finger in the sparkplug hole,
crank the engine until you feel compression. Then line up the TDC mark on the balancer with the pointer on the engine block.

The distributor starts out with the #1 plug wire lined up at about 12:00 with you facing it. Align the rotor to about 11:00, since it will turn clockwise as it slides into place.

Align the distributor rotor up with the #1 position marked on the cap, slide the distributor down into the block, (you may have to wiggle the rotor slightly to get the gear to engage) and then note where the rotor is pointing.
If it still lines up with #1 position on the cap, install the clamp and bolt. If not, pull it out and turn 1 tooth forwards or backwards and try again. Put the #1 spark plug back in and tighten it down, put the clamp on the distributor, but don't tighten it too much, as you will have to move the distributor to set the timing. Note that there is no such thing as one tooth off on a 5.0 Mustang. If it doesn't align perfectly with #1 position, you can turn the distributor until it does. The only problem is that if you are too far one way or the other, you can't turn the distributor enough to get the 10-14 degree optimum timing range.


Setting the timing:
Paint the mark on the harmonic balancer with paint -choose 10 degrees BTC or 14 degrees BTC or something else if you have NO2 or other power adder. I try to paint TDC red, 10 degrees BTC white and 14 degrees BTC blue.

10 degrees BTC is towards the drivers side marks.

Note: setting the timing beyond the 10 degree mark will give you a little more low speed acceleration. BUT you will need to run 93 octane to avoid pinging and engine damage. Pinging is very hard to hear at full throttle, so it could be present and you would not hear it.

Simplified diagram of what it looks like. Not all the marks are shown for ease of viewing.

ATC ' ' ' ' ' ' ' ' ' '!' ' ' ' ' ' ' ' ' ' BTC
---------------- > Direction of Rotation as viewed standing in front of the engine.

The ' is 2 degrees.
The ! is TDC
The ' is 10 degrees BTC
Set the timing 5 marks BTC. Or if you prefer, 5 marks towards the driver's side to get 10 degrees.

To get 14 degrees, set it 7 marks BTC. Or if you prefer, 7 marks towards the driver's side to get 14 degrees.

The paint marks you make are your friends if you do it correctly. They are much easier to see that the marks machined into the harmonic balancer hub.

At this point hook up all the wires, get out the timing light. Connect timing light up to battery & #1 spark plug. Then start the engine.

Remove the SPOUT connector (do a search if you want a picture of the SPOUT connector) It is the 2 pin rectangular plug on the distributor wiring harness. Only the EFI Mustang engines have a SPOUT. If yours is not EFI, check for a SPOUT: if you don’t find one, skip any instructions regarding the SPOUT
Warning: there are only two places the SPOUT should be when you time the engine. The first place is in your pocket while you are setting the timing and the second is back in the harness when you finish. The little bugger is too easy to lose and too hard to find a replacement.

Start engine, loosen distributor hold down with a 1/2" universal socket. Shine the timing light on the marks and turn the distributor until the mark lines up with the edge of the timing pointer. Tighten down the distributor hold down bolt, Replace the SPOUT connector and you are done.

The HO firing order is 1-3-7-2-6-5-4-8.
Non HO firing order is 1-5-4-2-6-3-7-8

 

[Blown88GT]

Note that there is no such thing as one tooth off on a 5.0 Mustang. If it doesn't align perfectly with #1 position, you can turn the distributor until it does. The only problem is that if you are too far one way or the other, you can't turn the distributor enough to get the 10-14 degree optimum timing range.

That's good to know, thanks!
It should start right up. I checked the timing already this past week so should be easy to do it again. Timing light seemed somewhat dim even in unlit garage.

 

[Blown88GT]

Put in new distributor, started right up with old TFI. Was unable to set timining below 30BTC. Ran for a few minutes & died wouldn't start again. Put new TFI on same new distributor, started right up. Went for road test, same symptoms.
KOEO reads 14C - PIP circuit failure
Because same symptoms as old distributor which gave no code, it's probably been the PIP all along. I'll get replacement distributor & try again. If "no go" will get from Ford & pay whatever it costs.

Maybe getting close to solving this?

 

[Blown88GT]

Got 2nd distributor, 1 of the mounting holes for the TFI is stripped. On Monday return for refund of the distributor & the core (which is already gone).

Found Motorcraft distributor & TFI online for $300 at Mustangs Unlimited. Placed order for both but distributor is backordered until 12/1/11.

 

[mustangmutt]

If you're positive it's the distributor you can buy this MSD unit from Summit for $262.95

MSD Ignition 8456 - MSD Pro-Billet Ready-To-Run EFI Distributors - Overview - SummitRacing.com

Then with the money you save you could get the MSD coil too.

MSD Ignition 8227 - MSD Blaster TFI Coils - Overview - SummitRacing.com

 

[Blown88GT]

If you're positive it's the distributor you can buy this MSD unit from Summit for $262.95
...Then with the money you save you could get the MSD coil too...

...Found Motorcraft distributor & TFI online for $300 at Mustangs Unlimited. Placed order for both but distributor is backordered until 12/1/11.

Guess you misread? ...Placed order for both...
Already have a Crane PS91 coil.