Car Stalls won't restart.

Uncle_Joe

Original poster
Member
Jul 26, 2019
15
Texas
My Envoy 4.2L will start when cold. after a few minutes, it looses power. I floor it with no response but at least i got it off the road into a parking lot.
As soon as i let go of the pedal, it will not start again. I floor it and it will "run" while cranking but as soon as i let go of the key(when trying to start it), it dies- the whole time with my pedal to the floor.

I just got this truck which had a blown head gasket and i though that was the whole cause of this behavior(from overheating). When i replaced the gasket, I started it sitting running in my driveway for 30 minutes only to turn it off to do xyz and start it again fine a few times.

Now, i close the hood and in no more than about 10 minutes driving, this happened. I think the problem started earlier in that only a few blocks away from home, i floor it, but there is no pep- just a very slow acceleration.

Where to look at?

Any clue??
TIA.
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
Any codes? Is the REP light on? Have you double and triple checked all your connections and hoses? Timing chain put back timed correctly?

So it was doing the same thing before doing the head gasket?
 
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Uncle_Joe

Original poster
Member
Jul 26, 2019
15
Texas
@Mooseman When i first got the car it had the code for the variable valve timing bad(which i replaced in the process) I seemed to have misplaced my scanner to see if any new codes but it is behaving the same as when i first got it.
Tonight, I did notice the hose(where it connects to the air box) that goes to the fuel pressure regulator is breaking\taring. I am going to get some hose to replace that tomorrow. Could this make this huge a difference in performance??
I'll post what i find.
THX.
 

mrrsm

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Oct 22, 2015
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Re-Check all of your Intake Manifold Fasteners for being snugged up to 87 INCH Pounds of Torque and NO MORE. Please Do not "Freelance" and guess at this Task instead of relying upon a Proper Inch Pound Torque Wrench, as recently, another Member discovered that he "Accidentally went a Little Overboard" and wound up Snapping Off TWO of these Delicate IM Fasteners like Butter and making enormous trouble for himself in the offing.

Hopefully... You replaced those "Figure 8" shaped IM Manifold Gaskets with Brand New ACDelco ones. In the end... it is NOT the Excessive Twisting Down of those numerous 10mm Fasteners that Seals up the Intake Ports nice and tight against the IM... it relies instead upon the "'Plumpness" of those New "O" Ring style gaskets (... around $12.00 Plus S&H from RockAuto) in order to prevent any odd Vacuum Leaks from occurring.


ACDELCOIMGASKETS.jpg
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
During the head r&r, did you replace the cam phaser? I had that issue with a P1345 that eventually made the engine run rough. Wound up being a bad cam.phaser (not the CPAS but the cam gear phaser)
 

Uncle_Joe

Original poster
Member
Jul 26, 2019
15
Texas
MRRSM - I used a digital torque wrench and made sure several times to torque the bolts to 87 3 times before the final 90deg - after going around torqueing in steps ending @87.
I did buy the gaskets in a set and it included the manifold and exhaust gaskets\seals.

I found the vacuum line to the fuel pressure regulator was fraying. i replaced it with a new rubber hose and it helped alot.
I think i bought a lemon. I hear piston slap(i think) and the engine runs\idles fine but when hot it dies at idle. Blowby as the block heats up and expands maybe. I plan on doing a compression test asap.
 

DocBrown

Member
Dec 8, 2011
501
Fuel pump?

BTW, the 4.2 is known for being noisy. when I had mine I started listening to other GMT-360s/370s and I could always tell which had a 4.2.
 
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Uncle_Joe

Original poster
Member
Jul 26, 2019
15
Texas
Looking into the codes that came up, the first one was that the cooling fan was disconnected (my bad) being i connected it a few days ago but still have error, i cleared the codes (maybe a bad idea) the only code that returns is p0016 bank 1 sensor a (pending???). is bank1 sensor a the one next to the transmisson on the block or the one at the cam shaft?

TIA.
 
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Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
It's not saying a sensor is bad, it's saying that the timing between the crank and cam is off. Have you tried to do a CASE relearn? Usually has to be done after major head or timing chain work. If it won't do the relearn due to the error code, there might be an issue with the actual chain timing.
 

Uncle_Joe

Original poster
Member
Jul 26, 2019
15
Texas
Found a note that said Bank 1 sensor is the front on the I6. I replaced the front position sensor. The P0016 did not come back but now it says P0340... DOH!!!

CASE RELEARN. I doubt mine has that capability. I guess i need to bring it in for that then....

I lined up the marks, cleaned the area with solvent then painted marks so i know what to line up. I manually cranked the motor a few times to make sure the cams did not pop out and confirmed the marks in the end. I hope it didnt slip a tooth on the crank shaft... I can say it does run better now than before i did the cyl head job so i *think* it didnt slip down there.
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
Most shops that have a high end scanner can do this, or a dealer.
 

mrrsm

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Oct 22, 2015
7,639
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As per @Mooseman for the CPS and CASE Re-Learn Issues:

 

Uncle_Joe

Original poster
Member
Jul 26, 2019
15
Texas
Thanks. I found this video yesterday. I'm going to try bring it in today.
Hopefully when i do, no new codes pop up. :tongue:
Thx.
 
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Uncle_Joe

Original poster
Member
Jul 26, 2019
15
Texas
I got to thinking - As the car heats up, the performance drops to no response when i hit the gas but hte engine is still running. I couldn't get it to drive up a ramp to get under it.

Because it runs differently as the temp rises im thinking it is more that just synchronizing the sensors.
Anyone ever hear of the throttle position stepper wigging out as it heats up?

To test my theory, Im thinking of pulling the wires when it doesn't respond yet pedal to the metal. Im thinking if i remove the intake hoses, it will die before i can look. So maybe most of the bad running is because of that- given i still need the Synch.
 

Uncle_Joe

Original poster
Member
Jul 26, 2019
15
Texas
M.Mcmillen - i thought about that before. This was my previous TB car went bad but it barely ran. This one seemed run fine. I was going to rule it out this time and loosen the cat (like i did on my previous to confirm) but 1 nut on the cat stripped so i kinda gave up. I went back to it last night and just drilled a hold in the cat. Decent change in performance. Alot of white powder came out. New cat -another item to add to the list!!
It would be funny - but great if replacing this and the error disappears!!
 
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m.mcmillen

Member
Apr 29, 2016
554
Wisconsin
Hopefully you found the problem. If you drilled too far you might have gotten into the catalyst.

Another way to check is to pull the oxygen sensor in the manifold and see if that improves things.
 
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mrrsm

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Oct 22, 2015
7,639
Tampa Bay Area
You can confirm or eliminate the possibility of having Shattered Rare Earth Metal Impregnated Ceramic Honeycombs (Tan-Tope Colored: Brittle and Harder than Chinese Math) inside the CAT very easily by turning Off the Ignition and then after the Vehicle Cools Down ... getting underneath the SUV to approach the CAT Stainless Steel Body without getting BURNED.

Then take a Small Dead Blow Hammer and LIGHTLY tap around on the outer metal of the very bottom center of the CAT. If you can here what sounds like "Pocket Change Dropped into a Ceramic Cereal Bowl" rebounding from within the CAT... That is a Sure Sign that the Internal Honeycomb has been Broken Apart into Pieces ...and will be an unfortunate confirmation of your need to Replace The CAT.
 
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Uncle_Joe

Original poster
Member
Jul 26, 2019
15
Texas
Being drilling the hole with the powder coming out and the motor running smoother\better I figure safe to say the cat is clogged. I have ordered one.

So just 1 error code. hopefully (when the cat arrives) i can have the shop do the CASE relearn and hope this ends my saga.
 

Uncle_Joe

Original poster
Member
Jul 26, 2019
15
Texas
The truck seems to run "normally"now with the cat issue fixed. Now to find why it still stops running after a few minutes. I am trying to borrow a tool to test fuel pressure when it does stop running. I rented the tool from oreily's but i dont find any connector to screw onto the fuel line.

Anyone here know where i can find the tool that properly screws on?

TIA
 

mrrsm

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Oct 22, 2015
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Uncle_Joe

Original poster
Member
Jul 26, 2019
15
Texas
I saw that video. Thing is mine has the schreader(or however u spellit) valve next to the engine computer but the kit i rented from Oreily's - nothing screws on to this connector. I stopped on the way to work but the kit looks the same...
Being i dont do this for a living, i dont want to buy one only to use it again 15 years from now rather just borrow one.
Can anyone tell me of a car parts store that loans a kit that fits?

ps.

after fixing the cat, NOW when start from cold, it goes up to about 1400 only to idle down to 700ishRPM and it sat there running normal until a few minutes before just stopping.
Before, when it stops running, when i try to start it, no go but if i pump the accelerator while cranking, it fires now and then for a split second.
This is why im looking at maybe a low fuel pressure problem.
Am i looking in the right dir, anyone?
TIA.
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
Which line are you trying to connect to? 02-05 are return systems and the test port is next to the fuel filter. 06-09 are returnless and the valve is on the front of the fuel rail in an awkward position. ** Don't put a lot of strain on that port as it will crack the rail.
 

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