it's built into the throttle body, it could be a bad throttle body but I would verify fuel pressure as that cost's nothing
and/or even do a relearn of the throttle body
Three random shut offs while slowing to a red light.
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and/or even do a relearn of the throttle body
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olliec420
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OK so Im looking at this again. Had another random shut off yesterday. Again, slowing for a stoplight. Its been hot so I haven't looked into doing the power wires yet but I figured this I could do now. I put my OBD app on and took fuel pressure readings for a couple miles. The high and low aren't very good according to your numbers. Hopefully I can have it running when it happens over the next few days.
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it doesn't tell you what the low was? is that what the yellow marker is? 43.5 is probably fine, under 40 is probably not, not sure at what point it would cause it to stall out though
@swathdiver do you have minimum specs for fuel pressure?
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olliec420
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Yeah yellow was the low. But this was only from like two miles after I got that gauge configured on the virtual dash. I will run it more this weekend and in stop and go traffic. Hopefully to catch a shutdown. At that point, if the low is under 40 then I guess I'll be dropping the tank lol.
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Been looking for an hour and can't find a minimum pressure in the manuals. The only reference I found was to follow the instructions in a GM fuel pressure adapter computer that gets hooked up to the fuel rail.
I know that for 2008-2014 Gen IV engines, they run at 43.5 psi.
I wonder if @olliec420 can see the duty cycle or % that the pump is delivering. That may tell us something and we can compare it to ours with our Tech-2s.
and to do a leak down test
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olliec420
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@Doubeleive Thanks for that.
So without starting the engine, turned on key and it went to over 50 and then trickled down over about a minute or so. You see the red is the high mark where it came on and and then slowly fell to 43.1. I took the picture then and started the car because I had to go. Hopefully that is the right procedure. I saw a youtube video that said dont worry if it trickles down.
But ultimately I just need to monitor as I drive and when it shuts off, I need to look and see if the yellow had dropped a bunch. Ya know I should add a similar monitor for voltage to see if it drops too. That would tell me if its a problem with the power cables.
So without starting the engine, turned on key and it went to over 50 and then trickled down over about a minute or so. You see the red is the high mark where it came on and and then slowly fell to 43.1. I took the picture then and started the car because I had to go. Hopefully that is the right procedure. I saw a youtube video that said dont worry if it trickles down.
But ultimately I just need to monitor as I drive and when it shuts off, I need to look and see if the yellow had dropped a bunch. Ya know I should add a similar monitor for voltage to see if it drops too. That would tell me if its a problem with the power cables.
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olliec420
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Ok Im back on this. LOL. It has kept doing it, like every 2-3 weeks it'll happen once and I'll pop it in N and hit the start and it will start back so quickly. Then pop it back in D and go. Well today it happened in a less than ideal spot. I was turning in somewhere and it was right then so I lost power steering and brakes. Luckily no one was coming so I was able to deal but if someone had been there turning out, that might been an accident on my fault.
I keep the computer hooked up for a bit and didnt see any pressures below 41 PSI. But of course its never hooked up when it happens.
Previous owner had crankshaft sensor replaced at 138k (now 179k). I doubt its that but I know his shop used a cheap-o and I kinda want to replace it with an OEM.
But of course there are no codes whenever it happens. Strangely enough, when the car shuts down I get no warning lights on the dash. No check engine, no battery light, no nothing. Just all gauges to 0. No interruptions to electricity for fans or radio. So I literally dont know it happened until the brakes and steering get tight. Im always moving when its happened.
I have in the garage waiting a new positive and negative battery cable. A new master bus fuse that Im going to start with. I dont think there's a problem with them but im going to go ahead anyway. I may go ahead and hit that crankshaft sensor too with an OEM too and checks it wiring while I'm down there replacing that cable to the starter.
The a/c compressor sounds awful but it works so well I dont even want to think about replacing it. Ive heard it sound that way on others from this gen so it must be kinda common. Now this just me thinking but could the a/c compressor pulls drag the engine down enough stop it at low RPMs if the bully was getting too tight from worn out bearings or something?
The most mind boggling thing is that I get no idiot lights on the dash when the engine stops running. Like when you turn the key to on and the engine isn't running you get CEL and BATT and others. I would expect the same thing... at LEAST battery light. Any one with any other thoughts?
I keep the computer hooked up for a bit and didnt see any pressures below 41 PSI. But of course its never hooked up when it happens.
Previous owner had crankshaft sensor replaced at 138k (now 179k). I doubt its that but I know his shop used a cheap-o and I kinda want to replace it with an OEM.
But of course there are no codes whenever it happens. Strangely enough, when the car shuts down I get no warning lights on the dash. No check engine, no battery light, no nothing. Just all gauges to 0. No interruptions to electricity for fans or radio. So I literally dont know it happened until the brakes and steering get tight. Im always moving when its happened.
I have in the garage waiting a new positive and negative battery cable. A new master bus fuse that Im going to start with. I dont think there's a problem with them but im going to go ahead anyway. I may go ahead and hit that crankshaft sensor too with an OEM too and checks it wiring while I'm down there replacing that cable to the starter.
The a/c compressor sounds awful but it works so well I dont even want to think about replacing it. Ive heard it sound that way on others from this gen so it must be kinda common. Now this just me thinking but could the a/c compressor pulls drag the engine down enough stop it at low RPMs if the bully was getting too tight from worn out bearings or something?
The most mind boggling thing is that I get no idiot lights on the dash when the engine stops running. Like when you turn the key to on and the engine isn't running you get CEL and BATT and others. I would expect the same thing... at LEAST battery light. Any one with any other thoughts?
does it completely shut off as if the key was turned off? no radio or ac fan still working? completely dead? until you cycle the key?
if so I wonder if it is a ignition switch problem
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olliec420
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No everything stays on just like its running. Radio good and a/c fans still run. And given the battery light not coming on, it doesn't even think the alternator stopped. Its crazy. And just my luck, I put all this money in and now some gremlin problem.
Like on a normal stall, you would expect dash lights, yeah? Like battery at minimum. Also every time, has been slowing down for a stop, or as of today, a turn.
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