i think i'm only running on 3 cylinders? could it be the intake manifold/gasket? - JeepForum.com
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Unread 05-02-2007, 01:33 PM   #1
9erHIGH
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1987 YJ Wrangler 
 
Join Date: Oct 2006
Location: maui no ka oi
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i think i'm only running on 3 cylinders? could it be the intake manifold/gasket?

in recent weeks i've noticed a loss of horsepower.
it's especially obvious when i'm accelerating from a stop,
or when i'm going uphill.
occasionaly (usually when i'm going uphill) i'll get a sputtering
almost like i'm running out of gas,
followed by a little lurch (like i just tapped the brakes hard.)

when idling it sounds like a cylinder isnt firing right,
and there is also a constant but somewhat faint smell of gasoline.

my cap, rotor, wires, plugs are all pretty new (18mos?)
one mechanic told me my intake manifold is cracked
and that is causing the problem.
is that possible?
i dont see a crack, but i think i'm gonna take it apart
and look at it closer. (rusted exhaust manifold needs to be replaced anyway.)
i want to get as good of an idea what possible culprits are first tho,
cuz i live on maui and gettin parts can take a while
if it has to come from the mainland,
and i dont want my jeep to be out of commission for too long...

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Unread 05-02-2007, 02:00 PM   #2
EABiker
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The best way to find an intake leak is to spray some carb cleaner or un-lit propane all around the intake/vacuum lines while the engine is running. Any change in RPMs indicates a leak> I would also pull and examine each plug to see which cylinders are miss-firing. It could be a cracked plug or bad wire as well. I'll help you personally if you send me a plane ticket!
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Unread 05-02-2007, 02:02 PM   #3
Michael_94YJ
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if your manifold is cracked you will know it because you will hear it. Probably is tho if its stock.
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Unread 05-02-2007, 02:13 PM   #4
9erHIGH
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Quote:
Originally Posted by EABiker
The best way to find an intake leak is to spray some carb cleaner or un-lit propane all around the intake/vacuum lines while the engine is running. Any change in RPMs indicates a leak> I would also pull and examine each plug to see which cylinders are miss-firing. It could be a cracked plug or bad wire as well. I'll help you personally if you send me a plane ticket!
k. i'll try that (not the sending you a ticket part tho, sorry)
but IF it IS in fact cracked,
do you think that would cause one of the cylinders to not fire?
if one of the cylinders isnt firing,
would that explain the problems i described?
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Unread 05-02-2007, 02:50 PM   #5
ltdanyj
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A bad enough leak will cause you to miss on a couple cylinders... but your other symptoms lead me to think that your timing is off....
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Unread 05-02-2007, 03:13 PM   #6
9erHIGH
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Quote:
Originally Posted by ltdanyj
A bad enough leak will cause you to miss on a couple cylinders... but your other symptoms lead me to think that your timing is off....

would timing "being off" start gradual and get worse over the span of several months? i've never messed with the timing so i'll probably have to refer to my hynes manual...

if the timing is off, would that explain the gasoline smell?
probably not right?

thanks for the feedback tho.
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Unread 05-02-2007, 03:55 PM   #7
joe's_yj
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i would just rplace cap rotor, wires and plugs, its not like its very expensive and then see if that helps
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Unread 05-02-2007, 04:22 PM   #8
9erHIGH
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Quote:
Originally Posted by joe's_yj
i would just rplace cap rotor, wires and plugs, its not like its very expensive and then see if that helps
there's no way that should be it tho.
i replaced those 18 mos ago.
now it will barely drive.
that doesnt make sense to me.
it sputters so bad right now.
i would think maybe it's a fuel line prob (pump or even filter)
but the engine must be getting fuel, or else why would the exhaust smell like unburned gas?
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Unread 05-02-2007, 05:19 PM   #9
BadAddetude
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Check the plugs and the plug wires. Sometimes if a plug wire is riding on hot metal for a while, it kinda melts thru and starts to ground out. or you could have a bad plug somewheres. pull 'em and look at it. sounds like an ignition problem, but thats my
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Unread 05-02-2007, 05:25 PM   #10
laredo_man
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could also be a clogged catalytic convertor .had a v8 that ran like a 4 banger with the loss of power.
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Unread 05-02-2007, 11:26 PM   #11
9erHIGH
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so, just to humor you guys (and to cross one thing off the list,)
i replaced my plugs and checked the cap, rotor and wires.
we're good there.
test drove it and same thing.
sputters pretty badly whenever i really apply the gas (going uphill
or accelerating from a dead stop.)

i'm gonna replace the intake/exhaust manifold gasket 2moro
and see where that leaves us.

any further suggestions?
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Unread 05-03-2007, 02:59 AM   #12
ChrisYJ - Italy
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Check very well the fuel system for leaks. My junk did the same thing, and was the pump-sender unit gasket on the top of the gas tank that was rotten dead. It seems that the system works well only if sealed.

There is a test procedure to check if your fuel system is pressure tight but can't find it right now, anyway it should be on any manual!

Good luck!
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Unread 05-03-2007, 05:20 AM   #13
EABiker
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Try disconnecting the exhaust after the cat to see if the guts from the cat are plugging the muffler; if the cat appears hollow when you look inside, it is bad and most likely the cause of your problems.
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Unread 05-03-2007, 05:58 PM   #14
9erHIGH
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Quote:
Originally Posted by ChrisYJ - Italy
Check very well the fuel system for leaks. My junk did the same thing, and was the pump-sender unit gasket on the top of the gas tank that was rotten dead. It seems that the system works well only if sealed.

There is a test procedure to check if your fuel system is pressure tight but can't find it right now, anyway it should be on any manual!

Good luck!
you know, there is a good chance that could be it.
i thought i had taken care of that issue...

i'm gonna double check something...

thanks for the suggestion!
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Unread 05-03-2007, 06:22 PM   #15
ChrisYJ - Italy
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Give it a good check and post up what it was, when you find the problem!

Hope it's a simple fix!
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