Start, Idle, Stall

[Moots12]

So for about 2 weeks I've been having a problem with my 06 Envoy 4.2. After I replace my ignition switch (might just be a coincidence) my truck has been difficult at start up. I will crank it over and it'll start but it will die after about 1-2 seconds of running, if I do that about 6-7 times my truck will start and run flawlessly. Checked the fuel pump relay and I did the recase procedure. It seems like I am either losing fuel pressure or the cam/crankshaft sensors aren't lining up correctly, but I do not have any codes what so ever. Anyone have any thoughts?

 

[tbuckalew14]

So for about 2 weeks I've been having a problem with my 06 Envoy 4.2. After I replace my ignition switch (might just be a coincidence) my truck has been difficult at start up. I will crank it over and it'll start but it will die after about 1-2 seconds of running, if I do that about 6-7 times my truck will start and run flawlessly. Checked the fuel pump relay and I did the recase procedure. It seems like I am either losing fuel pressure or the cam/crankshaft sensors aren't lining up correctly, but I do not have any codes what so ever. Anyone have any thoughts?

do you still have the old ignition switch? Maybe toss that back in(assuming it was still working at the time)and see what happens.

 

[Moots12]

do you still have the old ignition switch? Maybe toss that back in(assuming it was still working at the time)and see what happens.

The old one had all the symptoms of being a bad switch, I actually bought a new one from Rock auto and returned the one I bought at autozone. I've been having some problems with the quality of there equipment. It did not change a thing though.

I do want to add that if I shut my truck off and within 3-5 seconds of my truck being off if I hit the key it will start but if I wait any longer it will not.

 

[v7guy]

I've been trying to help solve this problem with Moots, it's the damndest thing I've seen. This has been going on for almost a month.

There's been a couple occasions where the entire instrument cluster has lit up for a second while he was driving, then it returned to normal.
Once in awhile there is a security light, but it seems to be intermittent as well.
Sometimes the truck starts first crank and runs great.
Usually it seems to take 6-7 tries before it stays running, and with every try it runs for a couple seconds, then turns off like you turned off the key.
Sometimes it won't stay running at all and you'll kill the battery trying to get it to stay running, it just fires up and dies after a couple seconds and never stays running.
Then you can go out 15 minutes later and it'll fire up and run great.
There is no difference if the motor is hot or cold, it's just as likely to stay running (or not).
When it's running it acts completely normal and everything seems fine, but you never know if it's gonna start after you turn it off.


One GM dealership couldn't figure it out, and a shop that specializes in electrical work has said they can't figure it out.


Compression is good on all cylinders, ignition switch and ignition cylinder has been changed, as well as a flaky coil pack and the fuel pump.


I've worked on vehicles for over 10 years and I'm at a loss. Anybody got any more ideas?

 

[The_Roadie]

Monitor the fuel pump relay or the harness going to fuel pump to see if it's the root cause of the stalling. If it is, then work backwards (BCM, Security, ignition switch feeding the fuel pump relay) to see if it's a power or control issue.

If a GM dealer with a Tech II can't figure it out, assuming the problem manifested during the visit while the tech was on the case, then all we can do is shotgun and guess.

But I'd certainly start with instrumenting the fuel pump. Wrap little wires around the blades of the relay if you can't locate the signals in the harness to tap into with a pin. I use this trick all the time to monitor circuits like the SAIS or fan clutch. Bring the wires back into the cabin where a passenger can look at them in real time as the problem happens.

Monitoring all the parameters you can with EFILive or Torque may also help, assuming you can't get hands on your own Tech II.

 

[budwich]

While you are at it, you might as well spend the $20 and get a fuel pressure gage (harbor freight or equivalent). It will certainly add info to your investigation of the pump.

 

[Moots12]

While you are at it, you might as well spend the $20 and get a fuel pressure gage (harbor freight or equivalent). It will certainly add info to your investigation of the pump.

I have fuel pressure. I am going to try that trick with the wires on the relay hopefully soon, so busy with work havent had time. Just picked it up from the mechanic it took me 20 minutes and almost about 40 attempts to get my truck finally started and brought back to my place. I also have called a more "reliable" dealership (the one I purchased my vehicle from) and hoping they can throw my truck on the scanner. But I will probably pick up a fuel pressure gauge and attempt to find the problem before the dealership since my appointment is next thrusday.

 

[bcchevy]

To bad you weren't a little closer!
I've got the gauge and whatever else you would need

Def sounds like fuel.. bad ground or connection

Ck all your battery cables as well
Had some rust build up and didn't have a great ground all the time.

Good luck moots

 

[Moots12]

It was the Ignition cylinder housing.

 

[IllogicTC]

It was the Ignition cylinder housing.

My guess would have been something ignition-related if I had seen this post in time.

All the lamps on the instrument illuminating sounded too much like the "POST" the cluster does when turning to the Start position.