Stalling truck

Asked by Apr 25, 2016 at 06:21 PM about the 1997 GMC Sierra 1500 C1500 SLE Extended Cab SB

Question type: Maintenance & Repair

Hey I have a 1997 gmc 1500 5.7L v8 vortec has
385,000 km, does anyone have an idea why my
truck starts normally then I can drive it but then it
New water pump
1 year old spark plugs
New ignition coil
New coolant temp sensor
New thermostat
New starter
New fuel pump/assembly
Have looked up tones for every sensor for my truck
but all seem to be the same
So can anyone help why it's stalling on me? What
could it be?

22 Answers


Any engine codes? And you say new fuel pump assembly. Have you checked fuel pressure? Should be 56 to 63 lbs at the Schrader valve. And a bleed down test on the fuel pressure? An other thing would be a vacuum leak along the intake manifold, or anywhere else. Timing ok?

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Best Answer

Yes I checked my fuel pressure but before I changed my thermostat I had air lock in my fuel lines so I bled the air out and my fuel pressure is around 55 or so but my truck doesn't overheat it just stalls


I or you didn't mention anything about overheating. Check for vacuum leaks, and do a fuel bleed down test.

Okay, so I did scan it as well and it did say my mass air flow sensor but I unplugged it and it still died, would that be it?

And today it died in me like 9 times and I would die and turn key off then turn truck back on fired up but rpms went right to 2000 then back down to like 800 that happened twice


So what was the code? This would help.

P0102 which is mass air flow sensor


P0102 GMC - Mass or Volume Air Flow Circuit Low Input... Possible causes - Faulty mass air flow sensor - Intake air leaks - Dirty mass air flow sensor - Dirty mass air filter - Mass air flow sensor harness is open or shorted - Mass air flow sensor circuit poor electrical connection............... So in possible causes, you need to check for vacuum leaks, which on a Vortec is the intake manifold gasket that leaks since there is only 8 bolts holding it on, 4 on each side.


Also unplugging the MAF, yes it would die on you since it is attached to a major source of vacuum.

Okay I'll try that thank you for the ideas!

So checked for air leaks and can't find any, cleaned the maf with mass flow air sensor cleaner and it still dies, then I scanned it again and code p1406 came up could it be just dirty parts needing a clean? Or could it be the cat converter?


The cat would have to be pretty plugged up. I do believe a code would show up for that. Just look under the truck when it is warmed up, if the cat was plugged, it would be glowing orange. But this code indicates something with the EGR system, that very well could be...P1406 CHEVROLET - EGR Valve Pintle Position Circuit... Possible causes - Faulty Exhaust Gas Recirculation (EGR) valve - Carbon blockage of the pintle... The P1406 code means that the EGR valve is 10% of the expected position by the Powertrain Control Module (PCM), usually caused by carbon built up n the EGR valve. Start by cleaning the EGR valve.. The EGR pintle position was ±10% of the expected position... Possible symptoms - Engine Light ON (or Service Engine Soon Warning Light) P1406 Chevrolet Description.... The Powertrain Control Module (PCM) determines that the EGR valve is stuck open if the actual Exhaust Gas Recirculation (EGR) position and the learned closed EGR position vary by more than a predetermined value. The PCM tests for a stuck valve when the desired EGR position is at 0%. The PCM commands the EGR valve to 100% during certain driving conditions in order to clear a possible restriction from the EGR valve if the PCM determines that the valve is stuck open.

Okay I'll clean the egr valve and test that, do you think the idle control sensor would be dirty enough to make the truck stall and drive like crap?

And do you think this sounds like the cap and rotor?


Everything can be a factor. Check the cap and rotor for cracks, carbon trails, rotor would be burnt on the underneath side. If you are to inspect the throttle body, best take it off to clean & to be able to inspect the base gasket. Idle Air Control definitely cause grief as it is plugged into a major source of vacuum and do need cleaning along with the port it plugs into. This will be easier to clean out while the throttle body is removed. While your at it, the Throttle Position Sensor is another source of grief when it comes to acceleration. I believe these items can be tested to see if there good.

Okay I'll check those things anything else that you can think of that would cause this problem?


Well you have to realize I just giving you ideas on the symptoms you have at this point since I don't know the results of any testing. So this brings me to the distributor, I guess take out the Ignition Control Module and have it tested at Auto Zone. Check the spark to see what it looks like, it should be white, blueish in color, not an orange color.


Oh, I see there is a new coil, so the spark should be white in color. But still could check the ICM.

Yeah I know I'm just doing trial and error cleaning things and checking for leaks and what not and I looked at my ignition pickup and it's not orange


I think it is in the EGR system. Go over that real good. That EGR valve looks to be electrically run, it may be bad. It threw a code, and can cause hesitation.

I clean the egr valve the Pintle still works and it's not sticking

So I've been noticing my fuel gauge is bouncing around from three quarters to full to half then back that's a fuel pump sign right?

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