96 Tahoe Engine Swap - Starts, idles high then cuts off

[Peyton Gregory]

1996 Tahoe 4x4 4-Door 5.7l 350 Vortec

I recently toasted my engine after an oil coolant line burst. Before that happened the truck was running great. After that happened the engine started knocking from the bottom end.

I swapped my motor with a junkyard motor and put all of my original components on the junkyard block. The engine starts and the knocking is gone. When the engine starts, the RPMs jump to 4k and then the engine cuts off. It seems to accelerate smoothly without backfiring during the 10-15 seconds the truck stays running.

There is a check engine light code P1345. I swapped out the crank position sensor and that didn't fix the problem. Any idea what could be causing this problem?

 

[Fless]

I'm not familiar with that engine, but maybe the distributor is off a tooth or so?

 

[drakon543]

your distributor is off and you probably have a big vacuum leak allowing the engine to completely bypass the throttle. the distributor can only be off i think a maximum of 2 degrees from 0. that's what code p1345 means on your engine. your vacuum leak could be throwing off how far or little the distributor is off. also you can either eyeball the distributor or you need an advanced scan tool as a timing light wont work.

 

[liquify33]

There are apps and cheap scanners that can read the necessary info, but it won’t matter if it only runs shortly.
If you’re staring at the rotor with the cap off, the point should be right at the lower right flat corner of the distributor at cylinder 1 TDC. There is a mark on the balancer, but It’s faint. That should get you in the ballpark for timing.

No idea about the rev and die issue though. If it’s vacuum it would have to be one of the big hoses or a really bad manifold seal.

 

[drakon543]

the big hose near the back of the intake manifold is about the right size. i believe it was the brake booster yes i did it once. anyway there might be one other about that size just cant remember. liquify33 is correct just remember there is a tdc cylinder 1 for intake stroke and exhaust stroke. if its running at all your probably close so its unlikely you will need to go too far. patience and a steady hand you should be able to get it in place without the scan tool.

 

[willxfs]

I like the article in the link below for setting the distributor. You will still need a scan tool and rotate the distributor a bit to set the proper cam offset retard (thats the P1345 code you are seeing). Sounds like you are close. Good luck.

http://www.gmtruckcentral.com/articles/distributor.html

 

[Peyton Gregory]

your distributor is off and you probably have a big vacuum leak allowing the engine to completely bypass the throttle. the distributor can only be off i think a maximum of 2 degrees from 0. that's what code p1345 means on your engine. your vacuum leak could be throwing off how far or little the distributor is off. also, you can either eyeball the distributor or you need an advanced scan tool as a timing light wont work.

You are correct. There was a giant vacuum leak at the back of the intake and the distributor was off by a few teeth. Thanks for the help

 

[drakon543]

well whatever the cause i literally did the same thing on my last distributor change on my Tahoe. i had fixed the distributor as mine had the p1345 so i knew the dizzy was off. i didn't realize i had disconnected the vacuum line to brake booster. don't remember why exactly i had it disconnected it if i had done it accidentally or intentionally. either way i felt especially stupid as it took me hrs to realize it. i was literally on the phone with my gm tech guy sitting in the driver's seat when i noticed it.