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Old 01-12-2021, 10:00 AM   #15
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Yeah, Iíll deal with the EGR system first. So at some point I should have voltage going to the solenoid to allow vacuum through, and at that point I should have suction on the EGR valve, right? And if so, at about what RPMs should I be able to see the signal to open the EGR valve?
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Old 01-12-2021, 10:58 AM   #16
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The EGR valve is opened when:
ECT is neather too cool nor too hot
TPS is part throttle
PIP is between minimum rpm and maximum rpm


All of these have to be meant for the PCM to open the EGR valve.
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Old 01-12-2021, 11:31 AM   #17
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During a KOER Test (key on engine running) the ECM will test the EGR system.

This youtube video is just a quick version to get the point. There are many websites and videos on how to do KOEO & KOER tests.

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Old 01-12-2021, 07:16 PM   #18
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Randolpho: Iíve done the tests and get 111 and 172. So the question Iím working with is to prove or not that the EGR system is performing properly. Iím not getting a specific code on EGR, Iím too ignorant to know if OBD1 throws off a code if there is a problem. Should I expect a code if the EGR is deficient?

I will be brute force testing it as Subford suggested by blocking it off and seeing if the idle surging stops.
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Old 01-13-2021, 08:23 AM   #19
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P0172 is Bank 1 Too Rich.

The EGR is designed to allow metered exhaust into the combustion chambers equally (bank to bank) to reduce NOX. A leaking EGR valve should effect both banks and normally leans out the cylinders, not make them rich.
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Old 01-13-2021, 09:18 AM   #20
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P0172 is Bank 1 Too Rich.

The EGR is designed to allow metered exhaust into the combustion chambers equally (bank to bank) to reduce NOX. A leaking EGR valve should effect both banks and normally leans out the cylinders, not make them rich.
Well isn't this embarrassing!

P0172 is Bank 1 Too Rich for OBDII but Ford EECIV 172 is Right O2 Lean.

I guess it is possible for a leaky EGR valve to cause one bank to run lean depending how it's plumbed in the system. You did say that the EGR valve was replaced already. Pulling the vacuum hose off the EGR valve with no change eliminates the EGR solenoid & control. I really don't think it's an EGR problem but doesn't hurt to temporarily eliminate it.

Instead of using a flammable spray to find vacuum leaks, I use a jug of water and slowly poor it on various engine spots. You'll know when the water finds the leak if there is one externally. Some of the Ford engines where known for vacuum leaks on the PCV hose close to the Intake Manifold connection port.
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Old 01-13-2021, 08:16 PM   #21
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Well isn't this embarrassing!

Instead of using a flammable spray to find vacuum leaks, I use a jug of water and slowly poor it on various engine spots. You'll know when the water finds the leak if there is one externally. Some of the Ford engines where known for vacuum leaks on the PCV hose close to the Intake Manifold connection port.

Yes, that's all very well, but you need to go back and read my earlier post that says that it's only MAF systems that get lean when vacuum leaks cause unmetered air. This is a MAP system, and vacuum leaks do not cause unmetered air.
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Old 01-13-2021, 08:47 PM   #22
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Since this system only has ONE oxygen sensor, I wonder a) how it knows which bank and b) if in this case it simply means the entire system is showing lean?

Thinking out loud here, assuming the EGR valve and system is OK and I suspect it is, but will block it off to make sure, but assuming it is, and if I have no major vacuum leaks (Iím guessing I would have to have a Large leak to lean it out based on mpatonís thought regarding MAP rather than MAF. . . . Assuming, and once having proven, EGR is working correctly and no major vacuum leaks, what would you all do next?
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Old 01-14-2021, 08:15 AM   #23
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Yes, that's all very well, but you need to go back and read my earlier post that says that it's only MAF systems that get lean when vacuum leaks cause unmetered air. This is a MAP system, and vacuum leaks do not cause unmetered air.
A vacuum leak (unmetered or not) will lean out the fuel mixture whether it's a MAP, MAF, or non-EEC system.
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Old 01-14-2021, 09:47 AM   #24
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He said "vacuum leaks do not cause unmetered air." IE, you can't have unmetered air because with an air flow meter strictly speaking there is no "meter".
Just some difference in the criteria the computer programming uses to report a lean code in a speed density system versus a MAF system. Not terribly important to this discussion I wouldn't think.
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Old 01-14-2021, 10:13 AM   #25
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A vacuum leak (unmetered or not) will lean out the fuel mixture whether it's a MAP, MAF, or non-EEC system.

You are gravely misinformed.



All fuel metering systems measure the amount of air going into the engine, and then compute the amount of fuel that should be delivered for that amount of air.


In the case of a MAF system, the MAF measures air upstream of the intake manifold. If a leak into the manifold happens, then that air did not go through the MAF and hence is not measured or metered. Because the fuel supplied matches the amount of air which is metered, and extra air that gets into the engine unmetered gets no extra fuel supplied, the mixture for the engine is leaned out.


In the case of a MAP system, the metering is the measuring of the vacuum level (or Manifold Absolute Pressure) in the manifold. So any leaks of air into the manifold will result in an increase in pressure, thus metering all air that gets there by any means.


So no air is unmetered, and no leaning of mixture happens.
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Old 01-14-2021, 10:26 AM   #26
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Since this system only has ONE oxygen sensor, I wonder a) how it knows which bank and b) if in this case it simply means the entire system is showing lean?

The PCM and the placement of the O2 sensor are both Ford design decisions, and so that PCM knows which bank the sensor is in. It is presumed to be measuring the mixture for both banks.


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Thinking out loud here, assuming the EGR valve and system is OK and I suspect it is, but will block it off to make sure, but assuming it is, and if I have no major vacuum leaks (Iím guessing I would have to have a Large leak to lean it out based on mpatonís thought regarding MAP rather than MAF. . . . Assuming, and once having proven, EGR is working correctly and no major vacuum leaks, what would you all do next?

No amount of vacuum leak of any size will cause it to be leaned out with a MAP system. If there were a large leak, you would find that the idle speed would be very high indeed.



If you are going to disassemble the EGR system enough to block it off, then why not clean the valve so that it doesn't leak, and then you can make it inoperative by removing the vacuum hose for your test. That way you can make it work again after your test by replacing the vacuum hose which will be way easier than taking it all apart again.


Remember that as well as reducing combustion temperatures, the EGR is also an economy device because it reduces pumping losses, so I can't see why you'd want to disable it.
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Old 01-14-2021, 11:11 AM   #27
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Idle speed is around 750-800 rpm, so no large leak would be indicated using that parameter as a diagnostic tool.

I am doubtful the valve is bad, even though it has a few years on it now, it was replaced by the shop that unsuccessfully worked on it as mentioned previously. Because the engine has a slight surging at idle I am working to eliminate all possible causes one by one. The surging is not enough to be troublesome to drive, but since I don’t know if there is any correlation between the surging and the lean sensor indication, I thought I would disable the valve and see if the surging stops.

This morning I started it and brought it up to temperature, with the vacuum to the EGR off, and the surging was minimal if there at all, however, when I put the vacuum line back on the EGR, the surging didn’t reoccur so I haven’t really proven anything. I had also pulled the wiring plug off the EGR. Once I put it back on, the check engine light went off, but that doesn’t mean I have stumbled across a successful repair. I think once I drive out on the highway, the lean code will still cause the light to come on, and I expect the idle surging will reoccur, again because I haven’t really done anything that would fix the problem.
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Old 01-14-2021, 11:20 AM   #28
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what would you all do next?

I think the best next thing to do is to manage to drive it while you monitor the fuel pressure.


The test which gives you code 172 is a slightly different test from that used today on OBD2 systems. The EEC-IV test first drives the system lean at a steady rate until the O2 sensor says the system is lean.


Remember that these sensors can't say how lean or how rich, just lean or rich. Assuming the O2 sensor says lean within a certain time, it then drives the system richer at a steady rate, looking for it to say it's rich within a certain time. If it doesn't make it within that time, then it gives code 172.


Probably you are using E10 gasoline like most of us, in which case your fuel mixture is already 5% leaner than Ford calibrated the PCM.


If your fuel pump is weak, or perhaps if your fuel pressure regulator isn't working well, then you won't see 40psi under significant engine load, and that will make the mixture lean.


You've explained why you couldn't do this yet, but don't skip it. The pump is a likely cause, and the test is easy to do.
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