XJ XJ6 / XJR6 ( X300 ) 1995-1997

96 VDP P0300/P0302/P1313. What to try next?

Old 07-26-2016, 11:55 PM
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Default 96 VDP P0300/P0302/P1313. What to try next?

My 96 USA VDP had these codes (and no others), and still gets them after I’ve tried a number of things, and cleared codes:
• P0300 – Random misfire detected.
• P0302 – Misfire detected – cylinder 2.
• P1313 – Catalyst damage misfire detected – cyl 1, 2, 3 (Bank A)
I understand that possible causes for all these are:
• Fuel contaminated.
• Fuel injector blocked or leaking.
• Ignition secondary circuit breakdown (coils, spark plugs).
• Fuel pressure low.
• Cylinder compression low.
• Broken valve spring(s).
Here’s what I’ve done so far, without improvement:
• Inspected old spark plugs. Nothing unusual.
• Installed new spark plugs.
• Got a new coil and cycled it through all six positions.
• Removed fuel injectors and had them rebuilt by Mr. Injector.
• Compression check (I didn’t record the values, but nothing seemed way off, nor were any two adjacent cylinders low).
• Bought a fuel filter (but couldn’t get the old one out, even with the special tools. Could have a pro install it. But doesn’t seem like it would affect one bank only.)

Symptoms (besides the recurring codes):
• Rough idle (consistent with missing).
• Some slight surging and hesitating at freeway speed.
• Some slight lack of smoothness when accelerating from idle.
Any ideas?
What should I try next?

Old 07-27-2016, 02:07 AM
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a) check wiring to each coil (continuity, voltage, etc)
b) clean throttle body
c) load test battery and check voltage to under-hood locations
d) check ground straps and ground points
e) check for coil(s) shorting (arcing) to valve cover
f) validate CKPS or simply replace if it's seeing its age
g) check fuel pressure
h) check connectors (clean?) at sensors and modules

Last edited by caldercay; 07-27-2016 at 02:10 AM.
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gbmtkj (07-27-2016)
Old 07-27-2016, 10:53 AM
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Thanks so much for the suggestions!
I'm not familiar with how to do a few of those things, but will check them out in the forum.

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