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Discussion Starter · #1 ·
Hi everyone, It's been a long time since I've been here. I have a 1986 720 st 4x4 with a 2.4 fi engine. I rebuilt it about 30,000 miles ago. It has been doing fine except for one thing. It started getting blow by, (I guess that would be what you call it) back into the air filter about 10,000 miles ago. I'm not talking a minimal amount. I'm talking about a lot of oil. Enough oil that it is all around the tbi. Does anybody know why this happens? I have to get my truck smogged here in California and I am thinking it's gonna fail. I was thinking about changing the air filter and cleaning the engine, crossing my fingers and just going for it. Any feedback you all have would be greatly appreciated.
 

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I am no Nissan Tech or any Tech guy for that matter. But it sounds like you have a PCV system problem. Moms jeep does that when things get clogged.

Just my $0.02
 

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yea, check your pcv valve and hoses.
 

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One issue with rebuilt engines and multigrade oil (i.e. 20/50) is getting the rings to seat. I like running straight weight non detergent for the first 1000 miles until those rings seat.

Nissan used a high nickle content on the blocks, so not unusual to see honing marks still on the blocks after 100K miles.

This will make everyone scream... only trick I've seen to "seat" the rings is to pour Bon Ami into the intake system! :eek: I cringe with the thought of doing that, so make it a last resort.
 

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Discussion Starter · #5 ·
Well, I passed smog, yeah! But I went ahead and ordered a new pcv valve. I figured I might as well, since I had to order both front axle shafts. I don't look forward to replacing either one.
I have heard about that Bon ami trick from another mechanic. Out of curiosity, just how would a person go about getting a powdery cleanser into an oily system without the powder clumping up? Is it the heat of the engine oil that thins it out? Has anyone here tried this? I think it would be fun to try it on a truck that isn't my daily driver.
Thanks for the help.
 
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