S-10 Forum banner
1 - 20 of 20 Posts

·
Registered
Joined
·
54 Posts
Discussion Starter · #1 ·
Okay here’s the deal. I’ve got a 1994 ZR2 CPI. Over the course of the past two weeks I’ve installed new distributor, fuel pump, both knock sensors, injector assembly, fuel filter, knuckle kit, egr block off plate, motor mounts, temp sensor, spark plugs, wires, upper and lower intake gaskets. Engine still has an excessive shake to it and will sometimes pop/cough out of the intake. My “service engine soon” light keeps blinking with no codes being thrown. Truck odometer reads 315K. I’m really tired of playing the guessing game. If I were to do a junkyard 4.3 swap, what engines should I look for? I’m willing to swap over my CPI intake on the new engine to keep it factory. What 4.3 should I use? It’ll only be the block/heads and internals I’ll be using. I feel like my current engine has internal issues. This swap transition will also give me a chance to refresh my transmission.
 

·
time to get cereal
Joined
·
5,664 Posts
Sounds like you are still playing the guessing game to me. Might want to have a mechanic look it over before replacing the entire engine.
 

·
B4U Task Force Admin
Joined
·
30,378 Posts
Unless you rebuild the current engine, I think you're pretty much stuck with an engine of the same year. You'd probably exchange one problem for another. The 4.3 seems to have changed just about every year until '96. At 315 K, the timing chain is probably changing zip codes every time you start it. They stretch a lot.
 

·
Registered
Joined
·
54 Posts
Discussion Starter · #4 ·
Unless you rebuild the current engine, I think you're pretty much stuck with an engine of the same year. You'd probably exchange one problem for another. The 4.3 seems to have changed just about every year until '96. At 315 K, the timing chain is probably changing zip codes every time you start it. They stretch a lot.
I want to say the timing chain was replaced about four years ago. I can’t remember as I don’t use this truck as often as I should. It’s literally a ranch truck. So I’ve probably driven it about 50 miles in the last year. It’s always had that raw fuel smell and nasty engine shake. I just now got it in my head to make it right and damned am I determined to do so! What does a rebuild typically cost on a 4.3? I can remove the engine and install.
 

·
B4U Task Force Admin
Joined
·
30,378 Posts
I want to say the timing chain was replaced about four years ago. I can’t remember as I don’t use this truck as often as I should. It’s literally a ranch truck. So I’ve probably driven it about 50 miles in the last year. It’s always had that raw fuel smell and nasty engine shake. I just now got it in my head to make it right and damned am I determined to do so! What does a rebuild typically cost on a 4.3? I can remove the engine and install.
Not sure on rebuild costs. Can you post a pic of the top of the engine? Is it the one with the Vortex cover and tuning valve in the middle of it? What about there plugs? Have you checked them after trying to start it? Wet...gassy? It seems like the nut kits leak after awhile. These are the lines that fail.


348446
 

·
Registered
Joined
·
54 Posts
Discussion Starter · #6 ·
Not sure on rebuild costs. Can you post a pic of the top of the engine? Is it the one with the Vortex cover and tuning valve in the middle of it? What about there plugs? Have you checked them after trying to start it? Wet...gassy? It seems like the nut kits leak after awhile. These are the lines that fail.


View attachment 348446

I replaced those already. The spark plugs look normal really..the second picture is when I was checking for leaks.
348447
348448
 

·
Registered
Joined
·
54 Posts
Discussion Starter · #7 ·
Just noticed the exhaust manifolds glowing red while idleing..catalytic converter is hollow. So no restrictions at all exhaust wise.
 

·
B4U Task Force Admin
Joined
·
30,378 Posts
I remember a little about that thread. Did you figure out your fueling issues? What about the timing? Distributor in the correct position?
 

·
Registered
Joined
·
54 Posts
Discussion Starter · #10 ·
I remember a little about that thread. Did you figure out your fueling issues? What about the timing? Distributor in the correct position?
Yeah timing seems to be okay, I advanced it a bit cause of a rough idle shake. That might be the cause of the glowing manifolds. The fuel stayed at 54-55psi running and key forward and well seems to be working decent. It’s just that shake like it’s unbalanced or something.
 

·
B4U Task Force Admin
Joined
·
30,378 Posts
Double check the ignition wires...easy mistake to make.
 

·
Been there Done it
Joined
·
12,485 Posts
Red exhaust manifolds can be late timing, fuel is still burning when it leaves the engine. Or rich mixture that isn't burning completely and is being reignited by the hot manifold. Or just the opposite, if the mixture is too lean your exhaust will be extremely hot. A bad O2 sensor can cause AF ratio issues by telling the ECM to add or subtract fuel incorrectly. The other possibility is the cat and you've said it was gutted.
The best bet for a rebuilt engine is a GM #12366017 94-95 Vin W 4.3L. Rebuilt by GM with all OEM parts. They have a factory in Mexico that does just rebuilds. Jegs seems to have the best price of $2400. I think these will soon be NA. Because of their age GM isn't building/rebuilding them any more.
 
  • Like
Reactions: Salty Crusty

·
Registered
Joined
·
54 Posts
Discussion Starter · #13 ·
I checked the oil cap and saw milky residue. I’m not sure if the lower intake gasket didn’t seat correctly or it’s a head gasket that might be bad. Is the oil cap milky a symptom of a bad lower intake gasket?
 

·
Been there Done it
Joined
·
12,485 Posts
You can get a bit of milkiness on just the cap from condensation. Especially if you drive short distances. A bunch on the cap is obviously a water problem.
 

·
Registered
Joined
·
54 Posts
Discussion Starter · #15 ·
It was odd cause I hadn’t experienced that till I did all the new parts along with that lower intake gasket. I’ll be disassembling shortly. I’ll post pictures with the findings.
 

·
Registered
2000 Blazer SAS
Joined
·
385 Posts
It was odd cause I hadn’t experienced that till I did all the new parts along with that lower intake gasket. I’ll be disassembling shortly. I’ll post pictures with the findings.
Did you change the oil after you replaced the intake gaskets?
 

·
Registered
Joined
·
54 Posts
Discussion Starter · #17 ·
Did you change the oil after you replaced the intake gaskets?
no, didn’t think I needed too. I replaced the lower gasket for fun really. I didn’t feel a need to do so just figured I’d do it for safe measure. I should’ve left it alone honestly.
 

·
Registered
2000 Blazer SAS
Joined
·
385 Posts
no, didn’t think I needed too. I replaced the lower gasket for fun really. I didn’t feel a need to do so just figured I’d do it for safe measure. I should’ve left it alone honestly.
Then there's a good chance that some coolant got into your crankcase. It's almost impossible to completely avoid it. I would change the oil ASAP, then just keep an eye on it. But it's probably fine.
 

·
Registered
Joined
·
54 Posts
Discussion Starter · #19 ·
I’ll make sure to do so, what could cause an auto acceleration? I can be adjusting the timing and it’ll auto accelerate and de accelerate on its own. No codes for anything such as the iac or Map. No vacuum leaks.
 

·
Registered
2004 Avalanche. 2001 V6 Extended Cab ZQ8.
Joined
·
1,339 Posts
Unfortunately the ability for your computer to detect issues is very limited. It can barely handled the fuel/spark maps. I am guessing by you saying auto acceleration you are referring to the engine surging (RPM going up and down on it's own). I have been working on this issue on a friend's truck for a while and have not been able to track it down yet. Surging can be caused by vacuum leaks, TPS, Exhaust leaks, MAP issues, IAC malfunction, and timing being off. These engines are really sensitive to their timing, and by the book you need to be at 0° with an error of +/- 2°. Your truck will surge if it is too far advanced.
 
1 - 20 of 20 Posts
Top