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Unread 02-21-2015, 12:30 PM   #1
mdoll
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Join Date: Feb 2015
Location: London, Ontario
Posts: 2
No power/no idle hot

91' Jeep YJ, 4.0 6 cyl

I have a bad rear seal and it's -35 so I dumped a can of rear seal sealant in the oil. Drove it for an hour with no issues. Pulled in for gas and filled the tank. Left the station and lost all power at 2000RPM. Could keep it moving on the flat in first and second gear but barely made it up even small inclines.

Now it starts cold and runs fine until it heats up. 1/2 block it again loses power over 1500-2000 RPM. Stalls when I hit the gas.

Once hot won't idle but evens out at 2000+RPM, but can't drive it at all. Dies when you take your foot off the gas and won't restart.

Ruled out the O2 sensor. Dumped gas line antifreeze and injector cleaner in the fuel and it hasn't helped.

Had it at a mechanic and they couldn't fix it. They suggested dumping WNNS tune up in a can in it. I tried that didn't help.

I'm stumped.... any ideas?

I bought a new TPS sensor but haven't installed it yet. It cranks up fine when idling and runs smooth after 2500 or so RPM. So I don't think that is it and would rather not burn the $70 for the sensor if it isn't the cause.

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Unread 02-21-2015, 03:15 PM   #2
mike134
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1989 YJ Wrangler 
 
Join Date: Aug 2014
Location: Cleveland, OH
Posts: 1,683
this sounds like a severe vacuum leak around the manifold. It only occurs after the metal has expanded. Use an unlit propane torch around the manifolds while the engine is at idle. Listen for a change in RPM. A vacuum gauge is a good idea if you have one. I have one permanantly mounted in the cab to monitor engine vacuum.

Also, check for a severe exhaust leak. how did you rule out the O2 sensor? did you unplug it to see if the situation improved?

Also clean out the throttle body and IAC valve with throttle body cleaner! very simple to do, takes about 20-30 minutes.

You should go to Autozone an borrow the fuel pressure gauge, its free if you leave a deposit. It just plugs into the shrader valve on your fuel rail. Read the pressure with the key in the ON position, at idle, and with the vacuum line disconnected from the fuel pressure regulator.

when was the last time you:
changed the fuel filter?
changed the air filter?
changed the spark plugs, wires, distributor cap?
changed the oil/oil filter? what oil did you use?
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Unread 02-21-2015, 08:12 PM   #3
mdoll
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Join Date: Feb 2015
Location: London, Ontario
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Quote:
Originally Posted by mike134 View Post
this sounds like a severe vacuum leak around the manifold. It only occurs after the metal has expanded. Use an unlit propane torch around the manifolds while the engine is at idle. Listen for a change in RPM. A vacuum gauge is a good idea if you have one. I have one permanantly mounted in the cab to monitor engine vacuum.

Also, check for a severe exhaust leak. how did you rule out the O2 sensor? did you unplug it to see if the situation improved?

Also clean out the throttle body and IAC valve with throttle body cleaner! very simple to do, takes about 20-30 minutes.

You should go to Autozone an borrow the fuel pressure gauge, its free if you leave a deposit. It just plugs into the shrader valve on your fuel rail. Read the pressure with the key in the ON position, at idle, and with the vacuum line disconnected from the fuel pressure regulator.

when was the last time you:
changed the fuel filter?
changed the air filter?
changed the spark plugs, wires, distributor cap?
changed the oil/oil filter? what oil did you use?
Thanks did you mean a lit or unlit propane torch?

Fuel filter who knows, air filter brand new, spark plugs, wires and cap are fairly recent. Oil is new, filter is not (waiting to replace the rear seal when it's not -35)

I am in Canada so don't have an autozone, but might have a fuel pressure gauge in the tool box. Can't remember. definitely have a vacuum pressure gauge.

Thanks for the ideas... wish I still had my garage. Just moved
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Unread 02-21-2015, 10:50 PM   #4
The_Goob
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1991 YJ Wrangler 
 
Join Date: Jun 2012
Location: Walcott, IA
Posts: 3,655
unlit of course. map gas, or even carb cleaner in a pinch. the theory is that if you have a vacuum leak it will suck in the propane and cause a change in idle as the engine burns it.
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Unread 02-22-2015, 01:17 AM   #5
mike134
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1989 YJ Wrangler 
 
Join Date: Aug 2014
Location: Cleveland, OH
Posts: 1,683
Like The_Goob says, unlit propane torch!

you can try NAPA, pep boys, O'reilly's if you have any of those. They all have tool loans. They want you in there buying parts, so they loan you the tools to do repairs for free.
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Unread 02-22-2015, 08:18 PM   #6
Que89YJ
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1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 16,272
Follow the directions on the link and check the codes. Post what you get.


http://www.jeepforum.com/forum/f12/h...codes-1257145/
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