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post #1 of 4 Old 08-01-2013, 02:52 PM Thread Starter
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1991 YJ Wrangler 
Join Date: Feb 2012
Location: Northwest Missouri
Posts: 77
YJ replacement engines

My 1991 with 6 cylinder is blowing oil out the intake (pretty bad). I've done things like replaced pcv or ccv valve (whatever its called) on valve cover. Replaced various parts like idle air control, tps, spark plug wires, etc, but it's not running real good. Some time back I sucked some water in the intake crossing a river. In a perfect world I would have shut it off and drug it home, but I was alone and hundreds of miles from nowhere, literally.

I have no idea how many miles are on the engine, I bought it used with a replacement odometer in it. I'm thinking of just replacing the engine or having it rebuilt. I'm not sure what my best options are here. I can turn wrenches, but I'm no mechanic. Anyway advice is appreciated. I would like this thinking running again.

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post #2 of 4 Old 08-01-2013, 03:16 PM
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1995 YJ Wrangler 
Join Date: Nov 2009
Location: Schenectady
Posts: 1,182
since it's still running at all, I'd say it's safe to say you didn't hydrolock...
for a start (if you haven't already) completely remove the valve cover and SOAK it in degreaser and use various parts cleaning brushes to thoroughly clean it out... making sure to get into the baffles on the underside - they tend to clog up and make blow-by even worse than the 4.0 is already known for.

buy, borrow or rent a compression tester and check compression and leakdown on each cylinder... this will give you a good starting point to diagnose if the engine is ok or needing a full rebuild/replacement

Sean B. - Schenectady, NY - 95 YJ, 350/700r4/NP241, JB Shorty SYE, 8.8 rear, 2" BDS, 1" homebrew shackles, Daystar 1" BL, TJ flares, 35x12.50 General Grabber AT2 on 15x10 Bart D-Truckers, Polyshield polycarbonate windshield, HD over/under crossover steering
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post #3 of 4 Old 08-01-2013, 03:18 PM
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1987 YJ Wrangler 
Join Date: Apr 2007
Location: west palm beach fl
Posts: 1,990
first thing I would do is run a compression test and see exactly where you stand.if it is bad replacing the engine with a good used one would be the cheapest way out. I had my 4.2 rebuilt at a machine shop and it cost 2,800 a few years ago.

Do everything with a positive attitude, it won't always work but you'll piss enough people off to make it worthwhile.

the voices aren't real but they sure have good ideas.
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post #4 of 4 Old 08-01-2013, 05:18 PM Thread Starter
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1991 YJ Wrangler 
Join Date: Feb 2012
Location: Northwest Missouri
Posts: 77
I had the valve gasket cover off when i replace that pcv/ccv valve and it was amazingly clean. I think I have a compression tester gauge around here somewhere if not I'll buy another one. Trying to find a YJ to salvage a motor from is probably not worth my time, but they put that same engine in the cherokee from the same years right? I can probably find a junk one of those if the engine isn't shot in it too. I'll start with compression test.
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