4.3 Intake issue leading to blown engine?
 

Hello all. Just a quick issue I heard of from a customer yesterday that we're trying to research further, though I'd ask on here! He has a 2nd Gen S-10 p/u 4.3 and I have the same in a Blazer. We were discussing all the typical 4.3 issues, and he recently heard something I'd like to share with my fellow Forum members. Supposedly he was told that the ever common intake manifold leak has been known to somehow affect something internal, perhaps a loss in oil pressure or something to that effect, in turn causing rods to malfunction and the engine to fail in the lower end. His customer has reportedly viewed a Service Technical Bulletin on this subject, and though I have done a small amount of searching, have not been able to find one. Has anyone heard of this or seen the Service Bulletin?

That seems to be my problem after replacing upper and lower gaskets. Trying to figure what exactly happend to mine.

IM leak I can't imagine leading to engine failure. Running rich yes.

MAF sensor will not change the air and the fuel provided will give it a rich mix thus not causing detonation. Just make things a little dirtier...

I say coincidence perhaps.

If the leak dumped coolant into the oil and the engine operated in this condition for some time, it definitely can cause bearing failure. Water does not lubricate anywhere near as well as oil. If you even suspect a LIM gasket failure, keep an eye on the condition of your oil. If it starts to turn milky, stop driving your truck or at the very least, change your oil often (like whenever it gets even a hint of milkiness) to buy some time.

The MAF will definitely have an impact on the fuel being provided. If you have any doubts to that fact, try disconnecting the fresh air return from the back of the intake hat with the engine running and then try to drive it. It will run horribly! The PCM uses inputs from the IAT, O2, & MAF are used to determine the load on the engine and thereby the IPW (injector pulse width) is calculated. Bad MAF readings can cause a lean or rich condition depending on the reading reported back to the PCM.

i think Kyle covered it nicely.

LIM Lower Intake Manifold Gasket failure
 

When my 1996 Blazer was at 148,000 miles, it began having a 'tick, tick, tick' sound at start up, then would go away after 10 seconds. It did this for about 3 cold starts ( in the summer ), I checked the dip stick to find the oil level was very high, I checked the radiator level, it was very low. So, there was a lot of coolant in my oil, and it is using the bottom of the oil pan, displacing the oil. So, at cold start-up, the oil pump pickup is pulling water through the oil pump first ( tick, tick, tick ), then getting oil, which was keeping everything quiet again. Okay, that said, if someone had weak neglected antifreeze, and a bad Lower intake manifold gasket ( LIM ), and it was below freezing outside, then the sump could be encased in a block of ice, and starve the oil system at every turn of the key. I think that would make a fair amount of ticking at first, then some knocks, then it might just say nothing at all. Hope this helps.

also they tend to leak at the front 2 corners alot. keep an eye to see if its wet

i had been driving my 93 4.3 cpi while it had a lower intake leak for awhile and i did the upper and lower gaskets and drove the truck for 2 days after i got it done and the engine blew due to antifreeze being in the oil and causing bearing failure.