1991 spark plug change over.
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CF Veteran
Joined: Mar 2015
Posts: 1,203
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From: Northern CT
Year: 1995
Model: Cherokee
Engine: Turbo 4.0
1991 spark plug change over.
I am curious why the transition to obd changed to the champion rc12LYC from the renix with the rc9YC? Why was an extended tip needed?
CF Veteran
Joined: Apr 2012
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From: Wisconsin
Model: Cherokee
From what I've read, the air/fuel mix is more uniform near the center of the cylinder (away from the walls). The extended reach plugs try to hit that sweet spot. Less unburned fuel = better emissions.
CF Veteran
Joined: Aug 2010
Posts: 8,357
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From: Canton, MI
Year: 1999
Model: Cherokee
Engine: 4.0
See if the below data will help.
I think when OBDII came along (California initiated) there was an effort to decrease pollution and increase fuel economy fleet wide so I think that is the reason for longer projection plugs.
NGK's answer to the Champion RC12LYC was the FR5-1. Talking to NGK Tech Support, their claim was that the extended shell was a request from Chrysler.
FR5-1
.
I think when OBDII came along (California initiated) there was an effort to decrease pollution and increase fuel economy fleet wide so I think that is the reason for longer projection plugs.
NGK's answer to the Champion RC12LYC was the FR5-1. Talking to NGK Tech Support, their claim was that the extended shell was a request from Chrysler.
FR5-1
.
CF Veteran
Joined: Aug 2010
Posts: 8,357
Likes: 103
From: Canton, MI
Year: 1999
Model: Cherokee
Engine: 4.0
Also,
I see that the cylinder head changed in 1991 from the 1990 C/N 2686 head to the 1991 C/N 7120 head (different exhaust ports).
The intake and exhaust manifold changed from 1990 to 1991.
The O2S changed in 1991 to an O2S with a longer pigtail (for the new exhaust manifold I guess).
Fuel injectors changed.
PCM changed.
I see that the cylinder head changed in 1991 from the 1990 C/N 2686 head to the 1991 C/N 7120 head (different exhaust ports).
The intake and exhaust manifold changed from 1990 to 1991.
The O2S changed in 1991 to an O2S with a longer pigtail (for the new exhaust manifold I guess).
Fuel injectors changed.
PCM changed.
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