0neHundredHammers

I have a '99 express 1 ton extended wheel base 8 cyl 5.7 vortec gasoline engine van.

my condition is this: I start the van and it runs between 12 and 25 minutes and then it shuts down. It won't start after that at all. However, 2 hours later it will, and do the exact same thing. Die. To me, I think the computer is reading something off, and shutting everything down.

Before the problem: Other than an exhaust issue, which I don't think is the cause, the only problem I have had is excessive jiggling the key to engage the ignition. This has led me to think of a passlock, hall effect issue, which I still haven't ruled out.

Things I've done: replaced the fuel filter. Did a fuel pressure test. Checked all the ignition components. I also did a test to check for intake manifold gasket leakage. All was fine with one exception. When I pulled the crank position sensor out I may have been too rough or it was shot, but it came out in 2 pieces. I replaced it with a new one. Unfortunately, before all of that, the obd wasn't working. Only after I replaced the crank sensor did I isolate the fuse that the obd was tied into.
Pulling codes. Once I got the obd working, it threw some o2 sensor codes, still not all that concerned with that, and 2 crank sensor codes. PO336 Crank sensor circuit A performance , and PO339 CKP circuit intermittent.
Now, I have the 4 book, dealer issued manuals, and it does call for a relearn procedure. However, this condition existed before the replacement, and there's a way to do it with out a bi-directional scanner on the highway. Which of course would mean the vehicle would run for more than 15 minutes.
I have back probed the 3 wires to the sensor and things seem to check out. Also, if there was a short, the van would be a no start.
Where I'm at: I will replace the ignition cylinder with a new one and hope the 12-25 minute shut off ends. I hope that it does, but the codes still bother me. If it works I can do the relearn on the highway. It probably won't though.

Lastly: some after market cks require shims. So i bought some. 14 bucks for 2 washers, thanks autozone. I tried 1, then 2. Then none. Same condition. I took a caliper and measured the distance for the tolerance between the sensor and reluctor plate and it was within specs of the book. So no shims were neccessary. Got my 14$ back. However, this is what I observed. There was oil on the sensor each time I took it out between tests. Now, the sensor is in the front of the motor, just behind the harmonic balancer, in front of the timing chain. I'm beginning to think that there might be a gasket I need to replace between the reluctor plate and timing case. A 5 volt reference isn't a lot of voltage, so perhaps I'm getting just enough of a drop to throw the computer off?
So, I'm down to a 2 case situation. Replace the ignition on the column, and a gasket which actually isn't all that hard to get to.
Anyone out there ever dealt with this highly specific issue? Any thing i missed? Any alternative theories? I would be ingratiated to hear from you. Thank you for reading. I know I'm long winded.

mountainmanjoe

did you check the catalytic converters?

0neHundredHammers

A design flaw of this vehicle is that there is no shock absorbing hangers on the exhaust until the muffler. So basically, the 4 into 1 off either side of the manifold drop down to 2 respective cats then join up with 2 pipes into 1 muffler. The result is that the pipes off the manifold become loose because of vibration and leak CO.
In addition to that, in my case, one of the 2 into the muffler has rotted a bit and there's a 3rd leak there. So I have all of that going on as the exhaust issue. I don't think that would cause the shutdown though. So I've kind of ruled that out. I will fix it, but I live in NE, and it's freaking cold.

mountainmanjoe

interesting, but doesn't answer the question.

Clogged cats WILL make it shut down.

wyn_fox

I didn't have the stall problem, but i could hear a bunch of crap rattling in the cat and had a code reading for it. it looks perfect on the outside but the noise drove me crazy. my first quick fix was i got under and just kept smacking it trying to loosing things up and there was a lot. i would try that and when it does start take it out and floor it several times to blow it out. never heard a noise since and code went away. It's a cheap fix and it won't hurt to try it. Worked just fine for me. Thank God lol..

0neHundredHammers

Thanks Joe, other than a visual inspection of the cats is there some other way to check them? Any tests I can run?

mountainmanjoe

you bet.

- One easy way is bang it with a hammer or 2x4 or something. Just lightly, you don't have to smash it. If it rattles then chances are the innards are falling apart.
- there should be an oxygen sensor upstream. You can remove that leaving a hole. If the vehicle runs better then you know. If the sensor doesn't want to come out or whatever then you can drill a 1/4" hole and fill it later.

wyn_fox

I used my hand so you can smack it pretty good. You will hurt your hand before hurting cat.

Irish_alley

when it does shut down do you still have fuel (injector signal) and spark?