Serious 4.0 toubles but I'm clueless
#1
Newbie
Thread Starter
Join Date: Mar 2017
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
Model: Cherokee
Serious 4.0 toubles but I'm clueless
Alright so I've had my jeep for years and of course it has its problems but this one leaves me clueless. Recently it's been having alot of problems and I'm fairly certain that they're tied together somehow. Alot of times when I start it it's very bogged down and doesn't want to idle (crankshaft position sensor symptoms but it was already replaced) and when I shift into 2nd it is bogged down but then backfires through the intake and after that it's normal. The other day when I started it, it was again idling rough at low rpm like expected but the exhaust was coming out the air intake. I know this because it was very audible and I could see the burning oil coming out. I shut it off immediately and when I started it again it was back to normal. No clue what's going on, PLEASE HELP!!!
#2
Have you done a compression test? You might have a bad valve. Cylinder not sealing, so loss of power, backfire, and maybe backpressure through the intake. That's where I would start anyway.
#4
Newbie
Thread Starter
Join Date: Mar 2017
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
Model: Cherokee
#5
Newbie
Thread Starter
Join Date: Mar 2017
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
Model: Cherokee
#6
CF Veteran
Join Date: Nov 2010
Location: In the middle of Minnesota!
Posts: 5,805
Received 99 Likes
on
88 Posts
Year: 1999
Model: Cherokee
Engine: 4.0
Your symptoms sound to be "fuel" related to me. Things I would recommend:
1. Test fuel pressure. You should have 49 psi, plus or minus 5 psi. You really need to start here. It's the most basic of testing data and easy to do.
2. Test your MAP sensor. It is partially responsible for your fuel/air ratio. Be sure that the vacuum line leading to this sensor is in good shape.
Good luck and keep us updated!
1. Test fuel pressure. You should have 49 psi, plus or minus 5 psi. You really need to start here. It's the most basic of testing data and easy to do.
2. Test your MAP sensor. It is partially responsible for your fuel/air ratio. Be sure that the vacuum line leading to this sensor is in good shape.
Good luck and keep us updated!
#7
Newbie
Thread Starter
Join Date: Mar 2017
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
Model: Cherokee
Your symptoms sound to be "fuel" related to me. Things I would recommend:
1. Test fuel pressure. You should have 49 psi, plus or minus 5 psi. You really need to start here. It's the most basic of testing data and easy to do.
2. Test your MAP sensor. It is partially responsible for your fuel/air ratio. Be sure that the vacuum line leading to this sensor is in good shape.
Good luck and keep us updated!
1. Test fuel pressure. You should have 49 psi, plus or minus 5 psi. You really need to start here. It's the most basic of testing data and easy to do.
2. Test your MAP sensor. It is partially responsible for your fuel/air ratio. Be sure that the vacuum line leading to this sensor is in good shape.
Good luck and keep us updated!
Trending Topics
#8
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,875
Received 1,526 Likes
on
1,238 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
How old are the plugs, wires, cap and rotor? Due to be changed every 30,000 miles.
#9
Newbie
Thread Starter
Join Date: Mar 2017
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
Model: Cherokee
#10
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,875
Received 1,526 Likes
on
1,238 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
#12
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,875
Received 1,526 Likes
on
1,238 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
I'll bet they're as old as the cap and rotor or older. Why not start there? Cap, rotor, and wires. That's normal maintenance that is long overdue.