[N]VH Issue? Pump Voltage? Nope, MAF vs RPM vs VE!

eddieleephd said:

Now that's contradictory, what code does it throw when you immediately flip the key back on? Implausible 109, or something else? This is likely the only hint you will get.


As said before it may be limited fuel, or limited by ECU.

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No, it is not contradictory, but I was writing more for brevity than clarity, so my bad.

If I leave the engine/car/ECU be and normally cycle the keys over a few seconds, no codes appear. If I quickly cycle the key, sub 1-second, because I'm merging onto the freeway and I *have* to go now, then the shortness of the power down event causes a brownout for the ECU. I'm not surprised that a code is thrown under those conditions.

Typically I have gotten an intermittent crank position sensor code when does appear, but it is not a guarantee. I did replace it as a precaution. That code only had a high chance of occurring if I accidently stepped back onto the throttle too aggressively and stalled out again within about 10 seconds of the first one, both with "flicked" keys.

I swapped relay 109's because, initially, this appeared to me to be similar to an electrical issue, largely due to very very very little info about the problem on the forums. People with different backgrounds will interpret the causes of unknown problems differently. I've never had anything of this car behave with such insistent immediacy so an electrical issue seemed most likely and relay 109 controls power to the ECU.

eddieleephd said:

The symptoms oddly enough resembles the crank sensor failing from the cut out at higher temps and RPM's. Could be a wire is broken enough that when it gets hotter it just stops conducting, or a bad ground that is causing a loss of connection. I suspect a lot more things than the 109 because of when it happens

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I've read your post and responded to the post in situ, so it is interesting that you mention the CPS as I've replaced it. The sensor and its cable are good, but that doesn't rule out wire breaks, which can be a nightmare to trackdown. Grounds are freshly clean in the past 3 weeks.

eddieleephd said:

Somethings phishy about the situation and you accusing the 109, if it were the 109 RPM's would have nothing to do with it, only temperature and time would vary. Don't solder it in, pull the plug from the rack it's clipped into and let it hang. The only way a good "updated" relay should fail is if too much power is being drawn through it and it's fouling. It's a normal 4 contact relay with a 5th small signal wire connected, the updated ones were to withstand higher loads. Technically you could split the output and use 2 to increase life and reduce the load through the relays

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I've considered this, but relay 18 that is right next to relay 109 on the '97 is also rated for 40 A. It gets rather warm and because it is OE from 01/97, I swapped it out with a similar part rated for 70 A. Wasn't sure if the waste heat was from the energized coil, or the load running through the relay. I did confirm through disassembly that the higher rated relay had larger contacts. Since this relay runs hotter than 109, I've also removed 109 from the suspect list.

eddieleephd said:

This vibration and the modifications involved only intensified a situation.

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Any suggestions for tracking down wire breaks with unbroken insulation? If the software "patch" doesn't solve the issue, this is what is on my list next, I assume.

Digital Corpus said:

No, it is not contradictory, but I was writing more for brevity than clarity, so my bad.

If I leave the engine/car/ECU be and normally cycle the keys over a few seconds, no codes appear. If I quickly cycle the key, sub 1-second, because I'm merging onto the freeway and I *have* to go now, then the shortness of the power down event causes a brownout for the ECU. I'm not surprised that a code is thrown under those conditions.

Typically I have gotten an intermittent crank position sensor code when does appear, but it is not a guarantee. I did replace it as a precaution. That code only had a high chance of occurring if I accidently stepped back onto the throttle too aggressively and stalled out again within about 10 seconds of the first one, both with "flicked" keys.

I swapped relay 109's because, initially, this appeared to me to be similar to an electrical issue, largely due to very very very little info about the problem on the forums. People with different backgrounds will interpret the causes of unknown problems differently. I've never had anything of this car behave with such insistent immediacy so an electrical issue seemed most likely and relay 109 controls power to the ECU.


I've read your post and responded to the post in situ, so it is interesting that you mention the CPS as I've replaced it. The sensor and its cable are good, but that doesn't rule out wire breaks, which can be a nightmare to trackdown. Grounds are freshly clean in the past 3 weeks.


I've considered this, but relay 18 that is right next to relay 109 on the '97 is also rated for 40 A. It gets rather warm and because it is OE from 01/97, I swapped it out with a similar part rated for 70 A. Wasn't sure if the waste heat was from the energized coil, or the load running through the relay. I did confirm through disassembly that the higher rated relay had larger contacts. Since this relay runs hotter than 109, I've also removed 109 from the suspect list.






Any suggestions for tracking down wire breaks with unbroken insulation? If the software "patch" doesn't solve the issue, this is what is on my list next, I assume.

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Testing for continuity/resistance is the only way to find broken wires. It's a bit of a pain but I'm quick to get my DMM out.
Generally I look for resistance in excess of .5ohms where others say greater than 1. My theory is that greater than .01with the DMM I have shows wear on a wire.
In my experience anything .5 and greater shows that the wire is degrading. But especially check right at the plugs the extreme bending there causes this to be a common place for breaks.
In my signature there are links to plug tool and pin tools, if you don't have them you should make some.

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The relay 109 does not power the ECM, the ECM is powered by a different fuse and sends a signal to the 109 to turn on everything else.

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Test lead resistance of DMMs can easily be 50 to 100 milliohms, but I didn’t consider the analog component of higher resistance from the contact of the break. Oxidation on the terminations can easily make resistance similarly high. I have a LCR meter with Kelvin probes I’ll probably use to eliminate lead resistance; overkill, but consistent.

I do have pin tools, but thanks for the tip.

I had a signal too high when I forgot to plug in the T14a connector behind the battery, took a minute to remember that one. Point being was the two codes that came up were 109 implausible and upper limit reached so be sure to check near the battery where the wires go into the t14a.

eddieleephd said:

I had a signal too high when I forgot to plug in the T14a connector behind the battery, took a minute to remember that one. Point being was the two codes that came up were 109 implausible and upper limit reached so be sure to check near the battery where the wires go into the t14a.

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his is not 121 pin ALH

his is msa 15 on a 1z or ahu, I dunno really

68-pin, MSA15.5, rebuilt 1Z. It’s akin to a stripped down EDC15 as there won’t be any codes for the 109

So, CPRV, case pressure relief valve. I don't recall it being something that causes issues like this, but what say you?

With the pump voltage map: kept IQ axis the same, kept the modified RPM axis going to 5250, and replaced all of the z-values, with the top going to ~4.98V with the 1.221001 factor applied.

Sudden stall, aka Warp Field Collapse, is still present. Still at 4000-4200 RPM at high load. With the new pump voltage map, VCDS logged a lower IQ *and* a lower voltage during the phenomenon. No codes. Group 19 still reports 0.78 V to 4.58 V sweep range on the QA. Doing a visual inspection of the range sweep will wait until Tuesday at the soonest, and other theories are welcome.

case pressure valve will make your timing advance flatline up high in the cold start valve duty cycle

The CPRV sets the maximum pressure that the pump case can reach, when the spring pin backs off it just lowers its maximum setting.
On the mechanically governed pumps it may have been a more integral part to proper operation, being that the CSV was just fed 12v until the engine was warmish. On our engines it doesn't really come into play often with the CSV being duty cycled (and the ECU setting codes when it runs out of available CSV range) more of a safety feature to keep the transfer pump from hydrolocking itself if the return line were blocked tight.

If I have read this correctly, you have increased the number of possible voltages to the IP. If so maybe you should decrease to the next level down and see if the issue persists there.
You have manipulated the position of IQ through hammer mod, and increased the voltage value, from what I am reading, to increase the amount of fuel that is being called for and injected. One would assume you have a lift pump for this setup, and that the pump isn't actually beginning to starve for fuel to inject.
In an earlier post someone said that excessive cranking would accompany the lack of fuel availability. However, this isn't necessarily true. Reality is if the forces of the cylinder and the force to pull the fuel to the pump were great enough you could theoretically stall the injection and the fuel would never make pressure to pop the injector and let the fuel through. It would then simply return through the fuel return line.


This theory mostly fits if you do not have a lift pump.

I’ve increased the dynamic range on the pump voltage map. The drop in IQ and voltage was not proportional to the adjustment to the upper limit. I do not have a lift pump, but timing and dynos show that I don’t have a restriction issue.

I’m aware that I can probably drop the torque limiter around the affect RPM range, though, that doesn’t explain why I have a reportedly lower voltage at the same fueling conditions with the same WFC that’s occurring. That said, what you’re describing is a fairly analog process and this is a very digital response.

Popped the top off and recorded the QA @ 240 fps. There is some minor hesitation midway through the sweep, but it's doing a full sweep now with a registered voltage of ~4.86 V. I'll button it back up and see if operating conditions remain the same and if things start stalling again with a registered sweep of notably less voltage, then I'll take it apart of clean it.

Edit: The magnetic flux is altered rather significantly by the top cover. Voltage returns back to the previous range once it is back on, even just resting.

Digital Corpus said:

Popped the top off and recorded the QA @ 240 fps. There is some minor hesitation midway through the sweep, but it's doing a full sweep now with a registered voltage of ~4.86 V. I'll button it back up and see if operating conditions remain the same and if things start stalling again with a registered sweep of notably less voltage, then I'll take it apart of clean it.

Edit: The magnetic flux is altered rather significantly by the top cover. Voltage returns back to the previous range once it is back on, even just resting.

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Yes, I've noticed that too. It may also be fuel filling in the gap between the parts of the sensor being slightly more conductive than air. Makes trying to recalibrate that sensor tricky if you've ever had one of those completely apart before. But generally, it shouldn't have to be exactly bang on a specific voltage number to work fine. So long as it's within the normal voltage ranges of min and max, it should be fine. And I believe something above 4.8V on the high end of the range may actually set a code for quantity adjuster upper limit reached, flashing glow plug light and all.

Yep, 4.8V is the limit before throwing a code. I’m out and about with some friends but so far I haven’t tripped WFC, but I am smokey. Looks like I was pushing the pump a tad too far and IQ adaption had an affect here too. A rush hood closure resulted in $45 and needing a new screen for my laptop though

If the fuel were [significantly] conductive, I’d be expecting signs of ox-redux. Granted it is a 10kHz sinewave used for control, but that pump has got to eat some current to operate since the QA is basically an electric motor.

Laptop repaired with upgraded screen, but one last thing I wanted to note here:
From my past post, which is why I kept saying it, there is a ~5.1% drop in BTU/gal for HPR vs D2.

A VE pump has a maximum fixed volume displacement of 70-125 mm^3 depending on pressure, according to Bosch (pdf warning). There are revisions 2 & 4 online, with 2 being the most accessible. Both quote the 70 mm^3 figure which is repeated commonly. Regardless of the volume, we'll treat it as fixed.

Diesel HPR has a specific gravity of 0.77 @ 15 °C & 0.79 @ 4 °C. D2 has a specific gravity of ~0.83 & ~0.84 at the same temperatures. I see my fuel temp get up to 60 °C which drops D2 to ~0.8 and HPR to ~0.67. The drop is proportionally greater for HPR than it is for D2 giving me less fuel to work with. I've been toying with a thermostatic controlled fuel cooler and this is a good case for one.

Collectively this means I have a reduction of ~17.5% of energy capable from my injection pump by switch to Diesel HPR @ 60 °C, if the reasoning is sound. I'd like to independently check HPR's density/specific gravity cause a near 20% drop is output seems rather big for back-of-the-napkin calculations...

Anyhow, going to log and test with the torque limiter cutting some fuel form 3500 RPM to 4250 RPM. Once I stop stalling, I can resume normal operations. Last thread post here.

Alright, I'm not convinced anymore that it's a pump voltage issue.

I've been doing a whole lot of logging with custom measuring blocks so I can refine N75 & boost pressure maps. I've captured "soft" and "hard" WFC's, such that with "soft" WFCs the fault or delta wasn't too significant and I can recover and continue driving without power cycling the ECU, but "hard" WFCs require a power cycle.

Even though I've triggered these with high amounts of fuel, ~48 mg/str @ ~4.25V since diagnostic values were not touched, I've had them trigger with ~23 mg/str @ ~2.75V. They invariably happen as a couple of RPM marks, though there is some jitter of +/- 250 RPM sometimes.

I've copied all of my modified maps to my tuner's last tune and looked at the output files for any differences; at the bit level. Nothing as found. Now, I did swap the codeblock assignments (VCDS knows this as soft coding) so they were in numeric order in the file. This lead me on a hunt and I found how to re-enable the clutch and how to adjust cruise control to disengage when popping the transmission into neutral when engine braking. This made me think that there is a software fix for this, but I haven't been able to find it.

I'm *really* tempted to loosen all the pins in the IP's harness, start the car, and remove then replace them one by one to see if I can create the fault *and* not have the ECU generate a code. This did originally, randomly happen under specific conditions (but only sometimes) without me touching the tunes from my tuner way back in 2014.

And the guessing continues and largely because I have had few logs to compare to. MAF trumps MAP. The logs I do still have for sure are the ones on my server from the day of 12 dynos.

The location the dynos were held at were at 1200 ft, 95 °F
My logs were usually conducted at 860-915 ft at night between 70 °F and 80 °F.

I have a nice Excel table to give me guidance for boost pressures. Invariably, I have problems right about 4200 RPM. This was with an IAT sensor that had a massive time constant compared to the one I have now. My MAF registered ~ 910 mg/stroke when up there on the dyno and ~3 bar absolute. Down here every WFC even that gives me an output at 4200 RPM (time resolution is a pain) shows me at greater than 910 mg/stroke.

I've looked at over a dozen logs with that. I have 2 instances in 1 log from that dyno day that have values on the underside of this figure.

Why is this figure important? This thread is why.


A large portion of that conversation is focused on one aspect of the MAF readout, mg/stroke. Though there is a solid conversation regarding its absolute limit, where that limit is reached per RPM is not discussed. That's largely due to the fact that volumetric efficiency was not known.

Here is the kicker. Today I was able to run a log to 4800 RPM. I tried a repeat of it and I have a WFC moment. The first run shows 4263 RPM @ 45.9 @ 900 mg/stroke and the second shows 4200 RPM @ 41.4 °C @ 912 mg/stroke. Yes, 912, I just changed my diagnostic limits to 1530 mg/stroke, aka 6 mg intervals. With the MAF's flow limit at 460 kg/hr, with the VE stated from my testing beforehand, the first instance hits the MAF flow limit at 899 mg/stroke and the second at 913 mg/str. If you allow for some quantization errors (+/- 6 mg/str), this is *way* more likely to be the cause of actual WFC than a 20 mg/str spread on fuel.

By the way, 460 kg/hr s near enough to 17 lbs/min. It wasn't the pump. It was a fully saturated MAF. Why did I get it at about 3500 RPM? Because I exceeded ~2500 mbar of boost, or about 1095 mg/stroke. Flat land never created a high enough load on the engine to cause this. I did centripetal driving on a heavily banked onramp when I had this problem occur. It was the MAF.