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post #31 of 75 (permalink) Old 03-05-2019, 03:25 PM
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First of all, let me say that I asked subford to contribute to this thread; he's posted just before me. He's very helpful on the FTE and IRV2 forums, and has access to good documentation, and has helped at least 20 times as many people as I have with practical advice, so don't be put off at all if you notice that he has only 1 post so far in this forum. I'm more of an ECU hacker, having tuned my 460 after a cam and CR change.

Quote:
Originally Posted by buddysharp View Post
Yes, I understand your comment on metered air. By unplugging MAF, I'm running in limp mode should be running maximum rich (I think).
That's not quite it. The MAF sensor measures the amount of air flowing through it, tells the ECM (we may have to use the correct term which is PCM not that Subford is here :-) ) and the ECM injects the amount of fuel that this air needs. Now suppose that there is an air leak into the manifold which bypasses the MAF sensor. That means that there is more air in the intake than the MAF sensor told the PCM about, so there isn't going to be any fuel to match this air that the MAF sensor didn't know about. So the mixture is going to be lean. You did the correct test for this by spraying fuel around to see if it would get sucked into the manifold and speed up the engine as the mixture gets corrected. So unmetered air makes the mixture lean, and too much unmetered air could stop the engine from running.

What I'm not so sure about is how much air needs to leak in in order to stop the engine. This is because I once had a 400 engined 79 Lincoln, and one day some 3/4" metal pipe with a flame trap on it going into the inlet manifold rusted through, and there was a very loud hissing noise, but the engine would still idle, although badly. So I suspect if you had enough unmetered air to stop the engine, you'd have heard it. So maybe the problem is in the MAF sensor wiring.

And that's why I suggested logging that MAF data. All you want to see is whether the PCM sees an increase in air flow when you crank the engine. If you don't, then as you've changed between 2 MAF sensors, maybe it's the wiring.

I must confess, I'm still suspicious of the fuel pressure. I know you've already tested it. If you test it again, do test it under load, perhaps by power braking it, but don't overheat the transmission.

I'll think some ore on what else might be going on.
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post #32 of 75 (permalink) Old 03-05-2019, 03:31 PM
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This seems like an easy test worth running.
https://easyautodiagnostics.com/ford...sensor-tests-1
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post #33 of 75 (permalink) Old 03-05-2019, 03:55 PM Thread Starter
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Quote:
Originally Posted by subford View Post
You may also have filings around the PIP sensor and you need to blow them out and that may help if not changing the distributor.
But if I see the PIP code once then I change the PIP sensor and that means a NEW distributor (not rebuilt).
You could also change out the PIP sensor but that means you have to tare down the distributor and replace the stator assembly.
If you change the ICM near the safetywall mounted on the Drivers fender make sure it is black in color as MP said above.
Thank you for weighing in. I can't keep replacing parts till it works unfortunately. One failure won't drive me to replace the PIP\distributor unless I win the lottery

I need to figure out what is failing before I spend any more money. Tough situation. It runs with MAF unplugged which basically means (I think) it's running in limp mode. Once warmed up, it will continue to run if MAF plugged back in (because I think it stays in limp mode.)

Running live data shows Fuelsys1 OL fault and Fuelsys2 error. 02s11 and 02s12 are both .59V, O2s21 is .58V. MAF is around 5.9 g/sec, shrtft1 and 2 both sit at -20.31 and longft1 and 2 both sit at -26.56. I'm guessing all of this data us useless since the truck was started with MAF disconnected.

I'm going to keep searching till I can understand what systems to test that will kill a cold or warm truck after starting and then rule them out before replacing anything else. Hoping someone can help point me where to start because after nearly 15 hours of reading postings and informational articles, I'm stumped.
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post #34 of 75 (permalink) Old 03-05-2019, 04:26 PM Thread Starter
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Quote:
Originally Posted by mpaton View Post
First of all, let me say that I asked subford to contribute to this thread; he's posted just before me. He's very helpful on the FTE and IRV2 forums, and has access to good documentation, and has helped at least 20 times as many people as I have with practical advice, so don't be put off at all if you notice that he has only 1 post so far in this forum. I'm more of an ECU hacker, having tuned my 460 after a cam and CR change.



That's not quite it. The MAF sensor measures the amount of air flowing through it, tells the ECM (we may have to use the correct term which is PCM not that Subford is here :-) ) and the ECM injects the amount of fuel that this air needs. Now suppose that there is an air leak into the manifold which bypasses the MAF sensor. That means that there is more air in the intake than the MAF sensor told the PCM about, so there isn't going to be any fuel to match this air that the MAF sensor didn't know about. So the mixture is going to be lean. You did the correct test for this by spraying fuel around to see if it would get sucked into the manifold and speed up the engine as the mixture gets corrected. So unmetered air makes the mixture lean, and too much unmetered air could stop the engine from running.

What I'm not so sure about is how much air needs to leak in in order to stop the engine. This is because I once had a 400 engined 79 Lincoln, and one day some 3/4" metal pipe with a flame trap on it going into the inlet manifold rusted through, and there was a very loud hissing noise, but the engine would still idle, although badly. So I suspect if you had enough unmetered air to stop the engine, you'd have heard it. So maybe the problem is in the MAF sensor wiring.

And that's why I suggested logging that MAF data. All you want to see is whether the PCM sees an increase in air flow when you crank the engine. If you don't, then as you've changed between 2 MAF sensors, maybe it's the wiring.

I must confess, I'm still suspicious of the fuel pressure. I know you've already tested it. If you test it again, do test it under load, perhaps by power braking it, but don't overheat the transmission.

I'll think some ore on what else might be going on.
OK, tested some more:

With fuel pressure gauge on, pressured stayed at about 33 under power braking. I'm afraid to drive around with MAF unplugged as it may kill and cost another tow truck ride.
Started with MAF unplugged, warmed to operating temp and plugged MAF back in. MAF hovered around 5.9 g/sec. at idle and responded with throttle.
I checked all the vacuum lines again, listening for leaks, and unplugged and replugged a few to feel for suction - all seemingly normal.
this is a dual tank model. one tank is full and the other about 1/3. switching between tanks shows no difference - if I had a bad fuel pump, I think switching tanks negates it as I have one pump per tank?
I disconnected the vacuum line at the EGR sensor and had no change while running (again, this is probably bypassed when truck is in limp mode)

I think I need to figure out how to diagnose at start with MAF plugged in. I have my software connected (FORSCAN) but no codes other than system not ready. I'm going to go drive now with MAF uplugged and go uphill so in case it dies I can coast home...

Thank you for asking another fellow gearhead to weigh in. I'm also going to go clean out the distributor with compressed air.

I did note that in the rain (it's raining here) both the ICM and the PCM harness are getting wet thanks to the PCM wiring harness ground wire being the perfect conduit for runoff under the hood. I removed and cleaned the ground wire and repositioned it slightly to cut down on the run-off. They were dry when all this started so don't think that's a factor - just a crappy little coincidence.

Last edited by buddysharp; 03-05-2019 at 04:30 PM.
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post #35 of 75 (permalink) Old 03-05-2019, 04:29 PM Thread Starter
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subford, I re-read my post and realized I may have been more harsh than intended. Thank you for the comments. I'll give it a shot but I really am out of money and gun shy at this point to replace anything else without a smoking gun. Not to mention potential divorce proceedings if I buy any more parts.
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post #36 of 75 (permalink) Old 03-05-2019, 04:37 PM Thread Starter
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Ran the Torque application again with MAF unplugged in order to get truck to run. Here are the results - not sure if they are valid since MAF was unplugged.

Mode $06 report generated by Torque for Android
================================================

Vehicle VIN: Not present
Vehicle Manufacturer: Unknown
Vehicle Calibration ID: Not present

Unit and scaling information are not supplied with the data from the ECU for this type of vehicle. Consulting the manufacturers service book for this information is recommended.

Test report:
------------------
TID:$01 CID:$11
- Rich to Lean sensor threshold voltage(constant)
Min: 512
Test result value: 1,024
PASS
----
TID:$01 CID:$21
- Rich to Lean sensor threshold voltage(constant)
Min: 512
Test result value: 1,024
PASS
----
TID:$02 CID:$11
- Lean to Rich sensor threshold voltage(constant)
Max: 32,686 Min: 32,850
Test result value: 0
FAIL
----
TID:$02 CID:$21
- Lean to Rich sensor threshold voltage(constant)
Max: 32,686 Min: 32,850
Test result value: 65,535
FAIL
----
TID:$03 CID:$01
- Low sensor Voltage for switch time calculation
Min: 0
Test result value: 461
PASS
----
TID:$03 CID:$02
- Low sensor Voltage for switch time calculation
Min: 0
Test result value: 461
PASS
----
TID:$10 CID:$11
-
Max: 45
Test result value: 42
PASS
----
TID:$10 CID:$21
-
Max: 128
Test result value: 5,198
FAIL
----
TID:$31 CID:$01
-
Min: 32
Test result value: 255
PASS
----


End of report.
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post #37 of 75 (permalink) Old 03-05-2019, 07:43 PM
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Quote:
Originally Posted by buddysharp View Post
OK, tested some more:

With fuel pressure gauge on, pressured stayed at about 33 under power braking.
I know I'm only replying to one or two of your points here. Thanks for testing fuel pressure again.

Power braking isn't quite as good as going up a hill at 3500rpm in 3rd with th ethrottle floored, but it's good enough for a start. I suspect 33psi is a little low, but I do expect Subford to come in on this one with an opinion.

What we do know is that the Ford design fuel pressure is 39.13psi ACROSS THE INJECTOR. That means that when the intake manifold absolute pressure lowers, then the fuel rail absolute pressure has to lower. This is the job of the fuel pressure regulator, and that is also why it has a hose on the top for it to sense manifold pressure.

Internally, the PCM uses pressure in units of inches of mercury, and close to 30 in Hg is atmospheric pressure, which in psi is 14.7. So what we don't know is what intake manifold absolute pressure you had when you power braked it (unless you had an accurate vacuum gauge) So, working backwards, if your measured 33psi absolute was a good reading, and you were delivering the full required amount of fuel for WOT and say, 2000rpm, that would mean that the absolute manifold pressure was 33 + 14.7 - 39 = 8psi if my math is correct

In theory, going to WOT would give you atmospheric pressure in the intake, but in practice, there are losses and I wouldn't expect quite that much. But 8psi is roughly 55% of atmospheric pressure, and I would expect 75% to 80%. I should probably go and review my tuning logs here.

That 3psi difference could be just measurement error, and may perhaps be explained by many things, but IF it's correct, t could explain your long term lean issues. It would NOT be enough to stop the engine from running.

And yes, you have one fuel pump per tank and some check valves to make sure that return fuel goes back to the tank it came from.
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post #38 of 75 (permalink) Old 03-06-2019, 01:08 AM Thread Starter
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Agreed, I don't think it would be enough to kill the engine. What's interesting to me is that with the MAF disconnected and the EFI running using the O2 sensors to mix fuel\air, the truck runs poorly at idle but runs just fine under throttle. I ran the hell out of it this afternoon and it was initially crappy but ultimately ran fine under load.

I'm suspecting that with an advanced tool, the answer will become obvious. ICM, PIP, O2, PCM, EGR sensor - one of these is failing at startup and kicking the engine to cut off air or fuel (I'm thinking air based on my feel) Wish I could get it running long enough to tell.

Man this is aggravating.
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post #39 of 75 (permalink) Old 03-06-2019, 07:59 PM Thread Starter
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Quote:
Originally Posted by subford View Post
You may also have filings around the PIP sensor and you need to blow them out and that may help if not changing the distributor.
But if I see the PIP code once then I change the PIP sensor and that means a NEW distributor (not rebuilt).
You could also change out the PIP sensor but that means you have to tare down the distributor and replace the stator assembly.
If you change the ICM near the safetywall mounted on the Drivers fender make sure it is black in color as MP said above.
Subford, I blew the debris out of the distributor but no improvement. There was a considerable amount that came out but looked more like dust than filings. I located a replacement full Motorcraft distributor but will replace the PIP sensor before and ensure it is the black one.

Can you describe or point me to any testing I can do to narrow down the issue? I'm still wondering if, given the multiple issues, I have a faulty PCM.
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post #40 of 75 (permalink) Old 03-06-2019, 08:24 PM
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Quote:
Originally Posted by buddysharp View Post
I located a replacement full Motorcraft distributor but will replace the PIP sensor before and ensure it is the black one.
It is the ICM that needs to be Black and not the PIP sensor.
You have said the the fuel pumps were running in some of the post above are you saying that the fuel pumps run all the time the key is in the run position with the engine not running?
If yes then yes you do have a bad PCM.

Last edited by subford; 03-06-2019 at 08:32 PM. Reason: added info
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post #41 of 75 (permalink) Old 03-06-2019, 08:33 PM Thread Starter
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Quote:
Originally Posted by subford View Post
It is the ICM that needs to be Black and not the PIP sensor.
sorry, thanks for the catch.
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post #42 of 75 (permalink) Old 03-06-2019, 08:57 PM Thread Starter
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Quote:
Originally Posted by subford View Post
It is the ICM that needs to be Black and not the PIP sensor.
You have said the the fuel pumps were running in some of the post above are you saying that the fuel pumps run all the time the key is in the run position with the engine not running?
If yes then yes you do have a bad PCM.
Subford, let me respond and try to summarize:
I don't think fuel pumps are running all the time but I certainly hear them build pressure at startup and I have pressure tested at the rail, both key on and running, as well as power braking to simulate load and pressure was nominal. All this with MAF disconnected. After driving truck for 10-15 minutes, I can replug in MAF and no change. But if I turn off the engine and try to restart, it dies immediately.

Basic problem is that truck died while driving and engine now dies immediately after strong start. No response to throttle as it dies. I happened to disconnect MAF and engine started and ran - it runs poorly at idle but pulls fairly well under power. Replaced MAF, same result. Codes were only for Bank 2 sensor 1 lean and of course for low flow at MAF (disconnected). With MAF plugged in , I can't get it to run long enough for testing. During dozens of starts and stops, it threw one code (P0320 if i recall correctly) that indicated PIP and you mentioned your experience indicated to replace even after one code - thus I'm sourcing a motorcraft new distributor.

I have replaced TPS, fuel filter (which was relatively clean), both upstream O2 sensors, and the fuel pressure regulator. I have two fuel tanks and while running with MAF disconnected, I can switch tanks with no change in performance.

My theory is that a air\fuel related sensor is failing at start and killing engine by either shutting off fuel or air - I'm guessing fuel given zero throttle response as it dies. I suppose it could also be spark but it happen too fast to tell. I'm unable to get it to run long enough to generate a code. I'm assuming engine goes in to limp mode with MAF disconnected and thus I'm able to start and drive - albeit with poor performance.

I removed and inspected the 1 yr old replacement PCM - no blown or leaking capacitors, but some minimal evidence of water intrusion on the bottom\outside of the PCM casing. No evidence on the inside. The PCM was replaced a year ago for a CEL (Bank2 Sensor 1 lean code) and the CEL returned not too long afterwards.

I've sprayed all injectors while running to check for leaks with no change in RPM. I also watched fuel pressure over a period of 15 minutes with key on and pressure remained constant.

I've used compressed air to clean out the inside of the distributor with no change. The rotor and cap were replaced in the last couple of years and show minimal wear.

Any suggestions on how to test to identify the fault?

Last edited by buddysharp; 03-06-2019 at 09:01 PM.
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post #43 of 75 (permalink) Old 03-06-2019, 09:38 PM
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The only thing I can think of at the moment is I heard of a similar case a few years ago and the problem was the PSOM. It was giving an over speed while the truck standing still and the PCM was shutting the engine off at start up.
You can try unplugging the PSOM and see what happens. This will make the transmission shift hard but we want to see how the engine runs with it unplugged.

This was mentioned above. Look over the Ignition switch and its plug as it can also cause a similar problems to your case. We are not talking about the tumbler but the switch down low on top of the column.

Also check the voltage coming from the TPS. It should be 0.90 to 1.0 volts at closed throttle and around 4.8 volts at WOT. It is best to check with an analog VOM so you can watch the needle move smooth with no jerks as you open the throttle.
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post #44 of 75 (permalink) Old 03-06-2019, 11:24 PM Thread Starter
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Quote:
Originally Posted by subford View Post
The only thing I can think of at the moment is I heard of a similar case a few years ago and the problem was the PSOM. It was giving an over speed while the truck standing still and the PCM was shutting the engine off at start up.
You can try unplugging the PSOM and see what happens. This will make the transmission shift hard but we want to see how the engine runs with it unplugged.

This was mentioned above. Look over the Ignition switch and its plug as it can also cause a similar problems to your case. We are not talking about the tumbler but the switch down low on top of the column.

Also check the voltage coming from the TPS. It should be 0.90 to 1.0 volts at closed throttle and around 4.8 volts at WOT. It is best to check with an analog VOM so you can watch the needle move smooth with no jerks as you open the throttle.
Thank you. I wasn't sure what the PSOM was but looked it up.

I went ahead and replaced the ignition switch and tumbler as I had already picked up spares. No change in start\die problem.

I will test the TPS voltage, but I will also check my running tests via Torque or Forscan as I believe I have recorded live data that showed TPS voltage while running with MAF unplugged. I'll check with an analog VOM in the daylight tomorrow.
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post #45 of 75 (permalink) Old 03-07-2019, 06:22 PM Thread Starter
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subford, I checked the TPS voltage, and engaged a Ford specialist to help with confirming ground connections and voltages across a variety of points. All good.

Using a SnapOn scanner as well as a full diagnostics machine, we found the PCM thought that the truck was at 4000ft elevation and would not accept any flash programming (hope I"m quoting him correctly). Bank 2 was maximum lean versus Bank 1 was maximum rich with all 3 O2 sensors performing and responding.

So our working assumption is fried PCM, despite no evidence of damage when I inspected several days ago. I've got one on order from Flagship One and will update upon arrival and further testing.
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