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Unread 09-15-2013, 06:23 PM   #1
JeepgrlFl
Registered User
1997 ZJ 
 
Join Date: Sep 2013
Location: Ormond Beach, Florida
Posts: 1
Check Engine Code po300

I keep getting a po300, 302, 303, 304, and 305 check engine light reading. I put in a fuel injector cleaner a month ago. I'm at a loss of what to do. My mechanic is no help and wants to charge me an arm and a leg to do bunch of things I didnt really understand. Any suggestions???

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Unread 09-15-2013, 06:33 PM   #2
Oldfrog
Web Wheeler
1997 ZJ 
 
Join Date: Feb 2008
Location: Louisiana/Texas
Posts: 4,241
Please complete your profile about your Jeep.
Which engine? What year model?...etc.

Ok...haha...I see you were doing that as I was typing.
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Cajun Recipes and Fishing tips

Words of wisdom, Posted by Zeejay:
"..it's not air, it is the opposite of air... suckage so to speak."

Stalling? Work through Zeejay's list
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Unread 09-15-2013, 06:38 PM   #3
Oldfrog
Web Wheeler
1997 ZJ 
 
Join Date: Feb 2008
Location: Louisiana/Texas
Posts: 4,241
Multiple misfires.
Symptoms?
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Cajun Recipes and Fishing tips

Words of wisdom, Posted by Zeejay:
"..it's not air, it is the opposite of air... suckage so to speak."

Stalling? Work through Zeejay's list
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Unread 09-16-2013, 07:38 AM   #4
newfieZJ
Registered User
1995 ZJ 
 
Join Date: May 2008
Location: , Alberta
Posts: 6,521
Typically , a tune up will cure this issue . Plugs , wires , cap and rotor .

Occasionally , a weak coil can do it . Bad grounds might make the coil signal weak also . Check and clean connections

Fuel pressure should be tested with a gauge , and can cause the issue if not right

Bad or poor signal from the crank position sensor (CPS)

Check wires around exhaust for any shorts

Lastly , valve springs . 97-98 apparently saw a batch of weak springs . Jeep has a TSB to address that problem which is nothing more than replacing the valve springs and cleaning the carbon that typically builds up from this problem out the combustion chambers causing the mis-fires .

Attempt a good misting with a water hose while the engine is running . See if it starts running rough . Good ignition systems can handle a little water with no effect .

Disconnect the battery , clear the codes . Give 30 mins disconnected to be certain it's cleared . As soon as the jeep tosses a check engine light , check the codes ASAP , report results here .
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Unread 09-16-2013, 08:30 AM   #5
johns1mj
Registered User
1995 ZJ 
 
Join Date: Aug 2013
Location: midland, michigan
Posts: 170
When you change your cap and rotor check the distributor shaft for movement. I have seen a couple of these "wobble" from the bushings going bad.
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