NEED HELP 2008 GMC Envoy issue with stalling

[rjohnson]

Hello.. I have a 2008 Envoy 4.2l . I had the engine replaced in April as it had a blown rod and purchased a used engine with 63,000 miles. When I got it back every time I stopped after it was warmed up it would stall. Since then it has been to 6 different mechanics and has cost me a lot of money and not one can fix it. I have changed the fuel pump, master air sensor, map sensor, throttle body cleaned, oil sending sensor, VVT solenoid twice, second one as the OEM. I am driving it with the VVT solenoid unplugged as it doesn’t stall then.. can anyone help me?

 

[Mooseman]

Any codes before the VVT was unplugged? Has a CASE (crankshaft angle) relearn been done? The PCM might still have the old engine's settings. If there was a code related to the VVT, the cam phaser may be stuck to advance, which could cause stalling. With it unplugged, the PCM may be compensating for the lack of phaser control.

If you can locate someone with an advanced scanner or a Tech 2, you could test the phaser by advancing it manually or seeing what the cam sensor is reporting as the degrees advanced. I know that at idle, as the phaser is advanced manually, it will run rough and eventually stall unless I give it some gas to prevent it. If yours is stuck advanced, it might be fine while in fast idle and running rich when cold but as soon as it drops, it would stall.

I assume that you did get an engine from an 08-09 as any from previous years would not even start.

 

[TJBaker57]

I am driving it without the VVT solenoid unplugged as it doesn’t stall then..

care to clarify this?

 

[TJBaker57]

@budwich

You have a 2008, right?

Have you ever tried to see the cam phase angle in Torque Pro?

 

[rjohnson]

care to clarify this?

I unplugged the VVT solenoid and it doesn’t stall, but the check engine light comes on.

 

[budwich]

@budwich

You have a 2008, right?

Have you ever tried to see the cam phase angle in Torque Pro?

Yep... a 2008. I have only looked at the "timing" pid which seems to have "funny" numbers at times ... based on my limited experience with "normal vacuum" advance system. The timing can show as much as 40 degree advance and a few degree of retard... would not expected such wide swings especially going from "constant pedal" to "no pedal" while driving. I am not sure what the cam phase angle pid is... and I haven't looked at my launch to see if there is one provided there.

sorry for the "mini hijack"...

 

[rjohnson]

Any codes before the VVT was unplugged? Has a CASE (crankshaft angle) relearn been done? The PCM might still have the old engine's settings. If there was a code related to the VVT, the cam phaser may be stuck to advance, which could cause stalling. With it unplugged, the PCM may be compensating for the lack of phaser control.

If you can locate someone with an advanced scanner or a Tech 2, you could test the phaser by advancing it manually or seeing what the cam sensor is reporting as the degrees advanced. I know that at idle, as the phaser is advanced manually, it will run rough and eventually stall unless I give it some gas to prevent it. If yours is stuck advanced, it might be fine while in fast idle and running rich when cold but as soon as it drops, it would stall.

I assume that you did get an engine from an 08-09 as any from previous years would not even start.

There were no codes prior to being unplugged..I will see about having it rescanned with your suggestions. Thank you

 

[TJBaker57]

I unplugged the VVT solenoid and it doesn’t stall, but the check engine light comes on.

OK. It was the "without being UNplugged" thing that seemed weird.

 

[rjohnson]

OK. It was the "without being UNplugged" thing that seemed weird.

Oops sorry for the typo…lol

 

[mrrsm]

Was your choice of a replacement Fuel Pump either an ACDelco or a Bosch version.... vs. choosing as the alternative ...an After-Market Fuel Pump?

On occasion, an improperly tightened Fuse Block assembly (via the Four Galvanized Bolt-Head Studs under the Plastic Fuse Box) can cause intermittent breaks in electrical activity. Try snugging them down and see if this makes any difference.




Lest I forget.... if your Mis-Fire Codes show up as very numerous on any One Coil Over Plug in any particular Cylinder... An over-heated Coil can create an Internal Dead Short Condition that will ALSO cause a complete engine stall.

Here is what is going on to make that happen:

(1) Failed COPs (Coil Over Plugs) are the RESULTS and NOT The CAUSE... by having repeated LEAN IN-CYLINDER CONDITIONS that force the COPs to work harder to create Spark Plug Firing Events.

(2) Whenever there is an insufficient amount of FUEL to Air Ratio... The Affected Coil(s) have to increase their Secondary Coil Voltage upwards in the Tens of Thousands of Volts that will oscillate back and forth so much that it will enter the Primary Side of the Coil Pack and generate enormous, damaging heat.

(3) But... After the Stall Event... Once the COP cools down enough, it becomes possible to restart the vehicle and do this "Wash - Rinse - Repeat" Dance until the coil finally fails completely.

(4) The Presence of a Flashing CEL is meant to Warn the Driver to Investigate these LEAN CONDITIONS... Soonest.

(5) The presence of any specific Cylinder throwing P0301-P0306 Codes warrants looking into having either a problem EFI, a Damaged or incorrect Spark Plug issue or the leaking in of air adjacent a portion of the Intake Manifold Three Figure "8" Intake Gaskets leaking ambient air directly into that Intake Runner at the affected Cylinder Intake Port. This can be caused after having --Snapped Off one of the Intake Manifold Trapped Fasteners-- nearest to that location after exceeding the limit of using only 89 Inch Lbs of Torque.

(6) Detection of an Over-Heated Coil Over Plug Aluminum Top "Radiator" should --NOT-- be investigated using Bare Fingers. Serious Burns may result! Instead, use a FLIR IR Camera and the issue will show its Ugly Face on the IR Camera Screen.