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1st code was MAF high output.
Installed new MAF.
Then threw MAF low output (i assumed that the computer had learned to compensate for the old maf?) ..then cleared itself.

Then a code of MAF high output happenned again about a week later,..and then cleared itself. (I was driving around the neighborhood starting and stopping over and over trying to get it to "stay stalled" so I could at least have a chance of knowing if the fuel pump is dying. By the way,..always starts right back up after the stall.

The stalling problem is always there once the car is warmed up. The code thing seems to be an intermittent type of thing....I suspect because the computer doesn't "read" the fuel pump or pressure??? Or does it????

Have inspected all the vacuum lines,, intake air ducting. etc.

Just now found an unused road and put it in REVERSE and did heavy acceleration...was cutting out just like you would expect if this thing is due to the same inertia as caused while braking...I'm sure due to the same inertia that was happening during heavy braking while going foreward.

I've cut a rather large access door over the fuel pump...the connectors appear clean and uncorroded.

Once the car is warmed up...and I start getting the stalling while braking condition.....the voltage becomes a little erratic,..and is lower than 14....but "usually" above 13.5..with a few spikes below that...I believe it is probably caused by the motor beginning to stall..because in REVERSE under heavy acceleration..the voltage doesn't appear to be dropping down,..even though the motor will cut out.

There are no codes right now.
In neutral it will stall or stumble when braking. (the braking has to be more than "light", as does the acceleration in reverse to get the same effect).

Also, in neutral,..it will stall when braking (when I say braking...I mean fairly heavy...like in rush hour)...even if you are coasting long at 40 mpg. It has nothing to do with "stopping" if you are in neutral. I suppose in drive..the tranny and foreward motion keeps the engine going until it is slow enough for the tranny to let go of it and let it die.

And, as I said, it will cut out while accelerating heavily in reverse.

Because I can induce the same problem with heavy acceleration in reverse gear,..(no brakes are involved), and cannot induce this to happen using the brakes while standing still idling...this is not consistent with vacuum problems involving brakes. Am I wrong?

A more complete description, and much more accurate,...is that this happens "with heavy decelleration" (or negative acceleration..whether it be brakes...or accelerating in reverse gear).

The brakes do NOT affect it if I am sitting still idling,..or if I am using them heavily while stopping in reverse gear.

With reduced braking power I could not induce the problem anyway unless I floored it in reverse...but without decent brakes that would make me nervouse,..even though the street is usually MT,..it is a residential neighborhood.

I've monkeyed with the connectors all over the place. yesterday I pulled the ERG,...ended up not needing cleaning but did it anyway.

A few days ago (with my fire extinquisher in tow)...I shot carb cleaner all over trying to find something somewhere where there may be a leak. Came up with nothing.

2 tidbits that may or may not help.

Without decelleration I went over a manhole cover that was half up and the bump made it do a quick stall (jerk) and then just keep going. Another thing...one night I was reproducing this over and over again in my neighborhood..and it stalled once and wouldn't start for 5 minutes...

OK, that's all I have.

OK - Not as likely if can happen without brakes. IDK why you think reverse matters except it's hard to go fast anywhere?
Been ages since a booster has been an issue I've personally been involved with. Was usually a vacuum hose to it if anything. If you've reset codes now with other attempts if booster anything was leaking that bad it would throw codes again soon. If bad enough of a vacuum leak other items would get poor vacuum and make wrong adjustments. TMK still vacuum to a brake booster must not share with any other vacuum item but if bad enough intake vacuum would drop for everything, run like crap or stall every time.
Take a look but don't think that's it right now yet at all,


T

You need a special adapter that goes into the end of the fuel rail to connect a fuel pressure gauge too.

The factory tool number is 09919-58421. Some of these master fuel pressure tester kits may have that adapter. At idle it should be 30-37 psi.

Have you attempted cleaning the throttle body bore and plate and then resetting the computer memory? Something easy to try if you haven't.

Just seems like a harness issue or bad connection somewhere, but you stated you checked harness, wiggled them around. Pay attention to how the harnesses are ran. Look for harnesses that appear to be rubbing on sharp object. Sometimes just spending 30 mins to an hour looking at wiring and other things can turn up the culprit.

If nothing shows up visually, it could be a difficult one to figure out without scan data and to see what goes missing right before the engine stalls out. When I usually get something like that, I do a good visual inspection, which it seems you have. Then check for codes and look at some scan data. If nothing looks unusual, then the lab scope comes out to look at injector and coil current or any other system that could cause stalls. Catching which system or systems stop working right before the stall can be challenge for an experienced tech. The good thing is your able to duplicate the concern.

One clue is the MAF codes that were showing up. Tracking down why those codes would appear could lead you to the culprit. Again you would need something such as a digital storage lab scope to monitor the signal, power, and ground at and from the sensor to see what is going on with that. It is also possible those codes could have set if you unplugged the MAF with the engine running.

I just put in a new tps (I broke the connector of the old one getting to the egr to service it..it was stuck..whoops),
I put in a new IAC to see if the old one was haunted or something.
Idles around 700 rpm,..had to adjust the new one (was idling really high till I figured out the slots were for adjusting it,...it had slots rather than holes like the original.

Took it for a drive,..took a while to warm up due to winter (it's below freezing a few degrees).Once it warmed up the problem was still there. On one of my heavy braking stops trying to make it stall....when it stalled...IT THREW A CODE. MAF high output.. I think thats P0103. I am not sure how to use freeze frame data, but I looked at it,..the fuel trims: one bank at 7 percent, the other at about 10 percent. Speed was 10 kilometers per hour, rpm was a bit over 1500 if I recall correctly..which makes me think the fault happenned closer to when I first hit the brakes..rather than when it was almost stopped.

After my initial stall this morning, it would stall every time I hit the brakes hard while stopping (I did not try accelerating in reverse at this point because there is snow almost everywhere...I could only find 50 feet of road without snow on it).

Here is one more piece of info. Once it has come up to temperature,..I can let it idle in the driveway...within 15 or 20 minutes it will stall (like if someone just shut it off) ..but start right back up easily. And then not stall while idling again for another 15 or 20.

AT THE POINT OF THROWING THE CODE, THE IDLE CHANGED TO 1100ISH RPM. I shut it off and restarted it....still idled high. Then I erased the code and the idle was normal. Still looks like a wiring thing to me, but I don't know what else to check with the wiring.

Since my MAF is new,...is there a chance the original and this one were BOTH bad??? My guess is that the original, as well as my replacement, were both good.
I do appreciate the input.

This has one fuel rail on each side...I think, it's a V6,...I am guessing that the two rails come together at the back down where it is very hard to get to. Since I've cut a hole for fuel pump access already,..I might just TEE in at the outlet. But I can't tell which of the two hoses is the outlet and which is the return...so I kind of stopped. I've been in the throttle body with carb cleaner and it looked awfully clean, I was surprised. I do not know what the "plate" is...so I probably didn't monkey with that unless I did it not knowing what it was. This was just carb cleaner stuff..I didn't pull the whole thing off or anything,..at my age...it's just not as easy the worse the arthritis gets. I did reset the computer memory shortly after I changed the MAF...that is when I cleaned the throttle body with carb cleaner.
I agree...it seems like a harness thing to me also. I tried to chase the main ground from the motor to the battery negative..and even with a mirror I can't see where it is bolted to the motor block..so I haven't checked the tightness of that yet. Haven't driven it on ramps yet to check underneath... I have poked my head underneath trying to find a spot where the wiring to the fuel pump may be rubbing...was hard to see much.
I have an o-scope (I haven't used it in so many years I might not remember how) and a few VOMs and DVOMS,, but they are electronic in nature..not auto (due to the business I am in) and other than checking voltage drop, current, and resistance... all I have for diagnosing a car is a regular auto-Xray scanner, and a wireless adapter that I use with my smartphone (much handier than the scanner..but hey....back when I bought the scanner it was big bucks..now they are cheap). When I bought the wireless I was hoping it would give me "everything".. but it doesn't even give me fuel pressure (maybe there isn't even a sensor on the car for this).

I have heard of rare instances where, as a motor wears out (NOT necessarily a fuel pump on a car)...if it's sitting one way it works...but sitting another way it will show open windings. Whatever the chances of that being the case here..I don't know,..but intertia is the same thing as tipping a motor.

As electrical connectors warm up the resistance increases.... but..it's like 32 degrees outside..you would think if it's an intermittent open circuit..it would be close to the warmth of the motor.

Do I "have" to check the fuel pressure at the rail...now that I've cut a hole in the back to access the pump??? Can I just plumb in my guage there? This is mainly because I don't know where the test port is and I doubt I would have the right fitting in all my plumbing junk.

I eliminated that by accelerating in reverse. No brakes in use..but still sputters. And,..I'm not sure I have any hypothesis whatsoever, why the inertia of heavy braking (or heavy acceleration in reverse) would be the only thing to induce a vacuum leak... And, on top of that, it is not that often that a vacuum leak will only happen warmed up...although I must admit I am out of guesses... My main guess is something electrical in nature because electrical properties change with temperature. And, in a car,.. the computer changes how things behave as the car motor comes up to temperature. For a while I had a hunch the fuel pump was intermittent..but the pump...how could it warm up if it is bathed in gasoline to keep it cool. That's the part I dont' understand. If I can find the test port I want to see if the fuel pressure goes to hell just before the fault.

Yes, I've tried to induce this by a lot of things. Knocking on the fuel pump,..monkeying with all the connectors I can find..,, The only thing that will induce it for sure is introducing negative inertia after the motor is up to operating temperature. (Either braking going foreward,..or accelerating in reverse gear.

Just FYI and think you know and not concentrating on it just how it works. Vacuum is highest at idle and when engine is used as a brake for example like downshifting for steep downhill driving no longer really done or useful.
The other side is when engines are working hard, up hills or especially WOT (wide open throttle) there is no intake manifold vacuum to be had to it's stored for use in a booster or other things when used so they will work when not directly available.


Booster should work with power assist a time or two with even a stalled engine! It would have boost the next day even. If unplugged (careful of the valve at booster can break) it should "whoosh" that it was holding. If not, why?


That's all. Carry on, Tom

One more (probably relevant) piece of info.
If I apply the gas when I am braking and coming to a stop,..the rpm will decrease but not die..then come right back up again...I do this in neutral.
I took off the iac and cleaned and tested it about 4 weeks ago and then put it back on.
but, because this is intermittent... (if it weren't for the fact that I can make it sputter, etc., by accelerating rapidly IN REVERSE)..I would be thinking put on another iac to make sure. I ordered one yesterday just to make sure. Is there any way the IAC could cause this while accelerating in reverse?????? I think not, but don't know where else to go with this.

For the AC/Heater system it appears from your description that the blower fan isn't coming on. You won't have an air coming from the vents if the blower isn't working.

The trick is to check the electrical circuits of the blower when the problem is occurring, to determine where the fault lies. To tackle something like this yourself, you would need an electrical schematic, volt/ohm meter, and a basic understanding of how the circuit operates.

The check engine light and ABS light are turned on by their respective electronic control units to indicate that there is a fault in one or more of the systems that those control units monitor. When a fault occurs the control unit stores a trouble code to help the tech determine which system/subsystem to begin diagnosing at. To get the engine codes you can plug a code reader into the diagnostic port under the dash. To get the abs codes you'll need an enhanced scan tool.

If you have no experience troubleshooting electrical circuits or the equipment on hand, you'll probably have to take it into a repair shop.