Kinda perplexed

nickb2

Wrench. Diagnostic Tech.
Joined
Nov 22, 2008
Messages
8,726
Likes
149
Points
63
Location
St-Hyacinthe, Quebec, Canada
#16
The original engine in my truck is a 350 5.7 was standard in the z71 k1500. The donor was indicated by paperwork to be a GM crate engine, same format 350 5.7 from a 4x4 Tahoe.
I am showing no major differences, if any, from a K series pick up and a Tahoe. A K series is by definition a 4x4. A vin "R" engine is a vin "R" engine and IMHO identical in a 96 4x4 tahoe than in a 97 K pick up.

The first generation 350/5.7l vortecs were made from 1996-98. Then slashed by GM in 99 for better injection.

Maybe the mechanic who is now pushing daisies meant that one was TBI and the other vortec. Either way, the block assembly stayed the same but I am pretty sure the ignition CKP reluctor wheel was different from one year to another. the 96 had only a three slot reluctor wheel while the 97 had a 4x or a 3x.

These weren't the best years of the 5.7l and that is why they varied so much and only stayed first gen for two years.

So as billr suggested, pull the crank sensor and count the teeth. However, if it is running and idle fine, that should imply all is good there, if not, this should be a no start instead of a stalling while in gear.

But for sure, they ARE THE SAME BLOCK.

The only thing I can really see here, is that one engine was maybe a vortec while the other was TBI. That would cause a start and run, but would be a bitch to keep running in gear if that were the case. An easy way to check that would be ECM service numbers from the donor vehicle to your Z71, but again, that is all long gone with the dead HOG loving, poker run guy.

Start there when you call the dealer, they would have that info. Alldata is quite generic and not as specific as a dealer database would be.

I hope I helped instead of confusing the issue.

My other humble opinion is that both the Z71 and the Tahoe taco both came with the sports package that had sequential vortec on board, so again, I am quite sure that if the info YOU have is correct, that the donor came from a taco 4x4, and put into your Z71, both engines should be plug and play all day long. This I know for a fact.
 
Joined
Mar 1, 2002
Messages
3,450
Likes
46
Points
48
Location
Kentucky
#17
If the truck uses the "crab" type of dist cap, many varieties of misfire are possible. Even if it is "new".
 

ej1619

Full Member
Joined
Oct 25, 2009
Messages
125
Likes
0
Points
16
#18
Bill, I will put my scan tool on it tommorrow after work and get some data and report back.

Nick, the donor engine is a vortec came complete with spider injectors. The donor looked about the same minus a couple small parts. Once I run the scan diagnostic I'll report back. My next step is to pull the reluctor and make sure everything is indeed correct and nothing is missing.

Dan, it is a new crab style I suppose I can swap it out and try again.
 

billr

wrench
Staff member
Joined
Mar 12, 2007
Messages
6,127
Likes
65
Points
48
#19
Don't fuss much with the reluctor, if the engine runs at all, it must be the correct style. Besides, it sounds like this reluctor is a simple 8-tooth one in the dizzy, not one down on the crank; correct?
 

nickb2

Wrench. Diagnostic Tech.
Joined
Nov 22, 2008
Messages
8,726
Likes
149
Points
63
Location
St-Hyacinthe, Quebec, Canada
#20
@billr, it is a 3 tooth/slot reluctor at crank. But this is for informational purposes only as we both have said that this is most assuredly not the problems as it runs and idles fine so pulling the sensor to count slots would probably be a waste of time.

Live data will give more info. What is spark advance doing at moment of going in gear? I am off to work, but I will talk to my co workers about this particular problem. Maybe of them will have an idea of any differences in the injection, ignition portion of this engine swap. But I think I will get back the same responses as I gave here. But hey, you never know. Will post back at end of work day after fighting montreal traffic.
 

nickb2

Wrench. Diagnostic Tech.
Joined
Nov 22, 2008
Messages
8,726
Likes
149
Points
63
Location
St-Hyacinthe, Quebec, Canada
#21
Again @ billr, there is a hall effect switch in the dizzy for cylinder identification, and the crank sensor is located behind balancer for crank shaft reference to the VCM for spark and fuel delivery. Those two have to be in synch and live data should also show that. Also, if the dizzy was a tooth off, a code must have set. So @ OP, run engine to operating temp for a complete warm up cycle, get all codes you can, record freeze frames if any, and report back.

I understand a complete drive cycle is not possible as it stalls in gear, but a warm up cycle will give long and short trims and tell us what the o2's are doing as well as spark and knock, and ect data etc. Also egr, tps iac and that good stuff. Ok, over and out.
 
Joined
Nov 14, 2006
Messages
4,802
Likes
50
Points
48
Age
118
#22
Are we sure it stalls in gear? I did not see that In OP.... or posted in a follow up.

But we are using a scanner SO maybe some insight soon.
 

ej1619

Full Member
Joined
Oct 25, 2009
Messages
125
Likes
0
Points
16
#24
Hey guys, thanks for all the input. I have had to set this to the side for a few days. I got hammered with work. The next day I have off work(or get in before bedtime) and I will get back to it and plug the scanner in. Hopefully tomorrow will offer some time.. Oh and to be clear, the truck never stalls out; it just starts skipping and is kinda low on power.
 

ej1619

Full Member
Joined
Oct 25, 2009
Messages
125
Likes
0
Points
16
#25
So sorry for the hiatus, that life thing again..lol Anyway back to the issues.. I finally fixed a couple things that needed to be done before I could drive it. Now when I first started driving it skipped bad not sure why, day 2 of driving the skip is gone and has started surging and kinda struggling at low speeds and when at cruising speed. When accelerating any at all it is near perfect. This now leads me to believe spider injectors are failing. Had a buddy tell me to scrap that system and go to tbi.. Any thoughts on this? Will I need to get get the computer reflashed for this? Or get one from a similar truck?