4.0 started running rough, I changed spark plugs, still runs rough.

Tiny
POP TERRY
  • MEMBER
  • 2002 JEEP GRAND CHEROKEE
  • 150,000 MILES
Plugs were long overdue. New plugs are the same # that I took out. When I disconect wire to fuel injector on # 1 cylinder, it makes no difference in how the motor sounds. When I disconect #2, I can tell a difference in the way it sounds. There was some codes, I cleared them after replacing plugs. They were 300, 301, 305, 340, 442, 455. Service engine light has been on a long time. Engine light is not on now, but the motor idols a little rough and when you start to drive it, it shakes bad. I think #1 plug is not getting fire to it. I took # 1 plug out, and it was clean, #2 & 3 had some black stuff built up on them.
Do you
have the same problem?
Yes
No
Thursday, February 23rd, 2012 AT 12:10 AM

3 Replies

Tiny
BMRFIXIT
  • EXPERT
Bad coil is a very common issue
p0442 p0445 is an EVAP system
Check canister vent solenoid
Was this
answer
helpful?
Yes
No
Thursday, February 23rd, 2012 AT 12:27 AM
Tiny
POP TERRY
  • MEMBER
Could the coil pack be bad and not show a code. Is there a way to check it to see if it is fireing. Thanks
Was this
answer
helpful?
Yes
No
Thursday, February 23rd, 2012 AT 1:36 AM
Tiny
BMRFIXIT
  • EXPERT
Unbolt the coil pack lift of spark plugs have a helper crank as you check for spark
Was this
answer
helpful?
Yes
No
Sunday, February 26th, 2012 AT 1:22 PM

Please login or register to post a reply.

Recommended Guides