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Discussion Starter · #1 ·
I DID A SCAN AND IT SHOWS A COMMANDED AIR/FUEL RATIO OF 29.3:1 WHICH IS OFF THE CHARTS. I'VE REPLACED FUEL PUMP, FUEL CONTROL MODULE, INJECTORS, AND ECM. WHEN I SCAN THE FUEL MODULE IT SHOWS A REAL PRESSURE OF AROUND 70PSI WITH A COMMANDED DEMAND OF AROUND 43PSI. HIGH PRESSURE RAIL IS GOOD AT ABOUT 740PSI, IT SEEMS WEIRD TO ME I HAVE HIGH LINE PRESSURE OF ABOUT 70PSI, NORMAL HIGH PRESSURE, BUT AM STILL RUNNING LEAN OFF THE CHARTS. WHAT DO YOU THINK? POSSIBLE LINE RESTRICTION? CAR STARTS AND THEN IMMEDIATELY DIES. THANKS IN ADVANCE.
 

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This post hurt my ears! 馃ぃ My dog ran out of the house yelping like someone was trying to molest it!馃槺
 

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Screen zoom works well. LOL
 

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I'm only a mechanic if there's a shade tree around...that said let me offer this...

First, Divotdoug makes a strong point...what did the info look like before all of the new parts? Could point you in the right direction.

But what if you're barking up the wrong tree? If the ecm is commanding such a stratospheric amount of air doesn't that mean its sensing that it thinks its running super rich? I think I would start by looking at the air management side now, specifically items like the oxygen sensors and the MAF. I would think that both of those would. trip a code but what if they didn't? FWIW I'll presume that your intake and such are not plugged although that might be something to check if you haven't already.
 

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I'm only a mechanic if there's a shade tree around...that said let me offer this...

First, Divotdoug makes a strong point...what did the info look like before all of the new parts? Could point you in the right direction.

But what if you're barking up the wrong tree? If the ecm is commanding such a stratospheric amount of air doesn't that mean its sensing that it thinks its running super rich? I think I would start by looking at the air management side now, specifically items like the oxygen sensors and the MAF. I would think that both of those would. trip a code but what if they didn't? FWIW I'll presume that your intake and such are not plugged although that might be something to check if you haven't already.
That's why I asked about codes. I can't imagine the A/F ratio so out of whack without any trouble codes, but I have seen an excessively rich mixture on my Corvette caused by a failed coolant sensor......which didn't trip any codes.....but it is an OBD 1 vehicle..

Like you, I would be looking at an issue with the oxygen sensors or MAF and their associate wiring harnesses.
 

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There are no codes. Checked them with multiple quality scanners
You've been chasing this for quite a while according to previous posts in other threads created by you. None of your 'fixes' has worked. Seems to me there could be a common denominator like a broken ground somewhere.
 

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In your post, you note changing the ECM. With what type of part? Salvage? Plug and play aftermarket? Genuine ACDelco? Reman?

Perhaps whatever you put in is not commanding the proper mix and/or throwing error codes appropriately? I would think a heavily rich mix would at least fire a P0420 or similar emissions code.
 

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Discussion Starter · #13 ·
In your post, you note changing the ECM. With what type of part? Salvage? Plug and play aftermarket? Genuine ACDelco? Reman?

Perhaps whatever you put in is not commanding the proper mix and/or throwing error codes appropriately? I would think a heavily rich mix would at least fire a P0420 or similar emissions code.
ECM was a remanufactured part programmed by All Computer Resources. Commanded air/fuel ratio has always been 29.3:1 since car quit running. I admit I'm a little confused about what that actually means--is it the present mixture or what the ECM is actually commanding. I'm using an Autel AP200 scanner. I guess I should call them and see what the reading means using their scanner. It's been a process. The first thing I replaced was the MAF because it was throwing codes. Upon smelling the oil it was very gassy. A mechanic friend of mine suggested changing out the injectors. I changed them all with brand new GM. Then I started getting a crank sensor code, so I replaced that along with the harness pigtail. I also started getting throttle body codes, so I replaced that with one from salvage. Then I used my brother's Foxwell scanner and it said I had a fuel flow problem so I put a new fuel pump in it. That didn't help either so I put a salvage fuel pump control module in. I haven't replaced parts just on a whim, but have always followed scan data. I'm thinking about re-programming everything through acdelco.tds with my pass-through device. I think I've followed the evidence but nothing seems to work. Perhaps I need to use a scanner that measures actual Air鈥揻uel equivalence ratio, (lambda) and see if it is less than or great than one. The cam sensor RPM being zero concerns me too. The cam counters work but the cam sensor RPM is always zero.

But I want to thank all of you for trying to help. It is very much appreciated
 

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Discussion Starter · #14 ·
You've been chasing this for quite a while according to previous posts in other threads created by you. None of your 'fixes' has worked. Seems to me there could be a common denominator like a broken ground somewhere.
Could be. And yes I have been chasing this for a while. Do you have an idea on how many grounds to body are on the Acadia?
 

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... Do you have an idea on how many grounds to body are on the Acadia?
AFAIK, there's one ground cable from the engine block to the body (maybe subframe). Sensors have 'bundled' ground points attached to various places on the engine block. Don't know how many, but they should be easy to visualize.
 

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Did you ever figure this out? I have the exact same problem on a 2013 Town & Country currently, and I'm stuck.
Um . .. . "Town & Country "?
Wrong brand. . . isn't that a Chrysler product? FCA . . . .?
 

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Um . .. . "Town & Country "?
Wrong brand. . . isn't that a Chrysler product? FCA . . . .?
You're not going to believe this, but many vehicle manufacturers actually use the same types of systems as well as functionally identical components in their vehicles, so it's not uncommon for certain fault conditions to produce the same results on many different vehicles.

This happens to be a very unusual set of conditions which are an exact match for my own, so the fault is likely the same despite the two vehicles being entirely different.
 

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I can understand that. Nevertheless, I guess no one has replied to the resolution and while sensors and general operation of A-F ratio control may be similar and even use the same sensors across brands. . . . the ECM or power control modules and implementation along with firmware would be vastly different.

I do wish you luck in your endeavor. Also, the OP who had these issues went on (if you view his profile and look and his "discussions") went on and apparaently had wiring/connector problems to the fuel pressure sender connector and also the ECM.
He never did come back and respond to any resolution.

I would think taking it in to a highly capable repair shop with personnel that can drill down into the fuel delivery operation parameters and any error conditions that may be buried layers deep and make, monitor and graph live data from what is happening might be the best for any resolution.
 

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Well, hopefully he does come back at some point if he hasn't figured it out, because I'm pretty sure I have the solution that he has been looking for.

The problem is with at least one of the cam sensors. The air/fuel commanded equivalence ratio of 29.3 is actually just a misinterpretation of the data by the scan tool, so that's basically a red herring.

The reason no codes are triggered is because when the hall-effect type CMP sensors (which the Acadia also uses) fail, they don't create a short circuit, open circuit, or even an abnormal voltage鈥攖hey actually even continue to send a signal just like normal鈥攕o the PCM can't see any fault. The problem is that the signal can become erratic, inverted, or stuck , so the PCM ends up triggering the fuel injectors almost continuously along with firing the coils randomly. The result is that at least one bank becomes total chaos and kills the engine almost immediately as it tries to achieve steady state. It very much mimics a fuel delivery problem, and since there are no codes, this should probably be on a list of the most elusive diagnoses out there.

The only way to I can think of to identify the problem reasonably quickly would be to plot the CMP signal waveform for each sensor using a scope and compare with the OEM specified 720掳 square wave plot. I highly doubt many people would think do check this right away though.

(Additional note: These sensors also tend to fail in sets, so it's best to replace them all at the same time.)

Well, hopefully this will help someone someday 馃憤
 
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