I am at a loss, help please
Thread Starter
Senior Member
Joined: Feb 2012
Posts: 627
Likes: 3
From: newjersey
Year: 2000
Model: Cherokee
Engine: I6
I am at a loss, help please
So Id say about march i got a check engine light, codes for misfires in 1,2,3,4, and random. and noticed a rough idle. replaced the spark plugs with bosch platinums and cleaned the throttle body. that worked and it ran fine. about june I got a rough idle again with the check engine light. misfires in 1, 3, 4, and 6. did an entire seafoam engine clean: oil, gas tank, through a vacuum hose and in the intake. that worked and it ran like a champ. just recently, id say about 1 week ago i went wheeling for the first time and didnt go to crazy. well check engine light came on day after and rough idle came back again. codes for misfires in 5 and 6, and random. replaced plugs with champion copper and reset. it worked and no light and no rough idle. cold start it idles great at about 750 rpm. after it warms up it idles at 500 with a tiny misfire. nothing crazy but it taunts me. I have read it is the coil pack, i have read it could be the cps. i am 17 so i dont have much money, dad gave me 200 bucks for helping out in hurricane sandy. was going to my lift but i figured a running jeep is way better than a lifted one. can i get some help and opinions on what it could be. I dont wanna blow the whole wad if i dont have too. sorry this is so long but i figured the whole story would be better. thanks!
Senior Member
Joined: Oct 2012
Posts: 989
Likes: 2
From: Gainesville,FL
Year: 1996
Model: Cherokee
Engine: 4.0
check distributor and wires from it to the spark plugs, check voltages and if you can bring it to local parts store to have the code read via the OBD2 port. if that doesn't help hit me up and I'll attempt to help you troubleshoot
Thread Starter
Senior Member
Joined: Feb 2012
Posts: 627
Likes: 3
From: newjersey
Year: 2000
Model: Cherokee
Engine: I6
I dont have a distributor, i got the coil rail/pack, whatever it is called. its a 2000. but right now i dont have the check engine light. it just went away but the codes pulled last were the ones for misfires in 5 and 6 and random. right now its got a little rough idle, and no light (for now)
Newbie
Joined: Oct 2012
Posts: 6
Likes: 0
From: arkansas
Year: 1998
Model: Cherokee
Engine: 4.0
I had the same problem on my 98 4.0 sport check your Ecu. Make sure the connectors are pushed in good. Also could be heat soak. Search heat soak in you will find plenty of info.
CF Veteran
Joined: Apr 2012
Posts: 5,302
Likes: 23
From: Wisconsin
Model: Cherokee
You may find this of interest:
So... one no-cost thing you may want to try is decarbonizing the engine. You can do that with a Coke bottle full of water.
Run the engine up to about 2K rpm and slowly dribble the water into the throttle body...enough to get it to sputter a bit, but no more.
Following that you may want to thoroughly warm up the engine and rev it up over 3,200 RPM a few times to rotate the exhaust valves. You may have to repeat both things a second time, depending.
0900303 - 4.0L MULTIPLE CYLINDER MISFIRE
Date: 08/01/03
Model Year(s): 1999-2004
Description: NOTE: THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH A 4.0L ENGINE. This bulletin involves inspection of all engine exhaust valves and a decarbonizing procedure if necessary.
Details: The customer may experience an incident of engine misfire during certain vehicle operating conditions. The misfire may occur when the vehicle is operated between 50 - 70 MPH and under light loading conditions, e.g. slight uphill road grades. This condition may occur at all ambient conditions, but is more noticeable when ambient conditions are less than 0 C (32 F).
If the vehicle is equipped with On-Board Diagnostic (OBD), a MIL illumination may also have occurred due to Diagnostic Trouble Code (DTC) P0300 - Multiple Cylinder Misfire. Various single cylinder misfire DTC’s may also be present. If the frequency of misfire is high the Powertrain Control Module (PCM) may place the engine in “Limp-In” mode.
The misfire condition may be caused by one or more engine exhaust valves that are slow to close. Late closure of an exhaust valve may be the result of no valve rotation and associated build up of carbon on the exhaust valve stem.
This condition may occur when the engine is not allowed to run at engine RPM’s that are greater than 3,200 RPM. At 3,200 RPM or higher the engine exhaust valves will rotate if not impeded by high carbon deposits. Low engine RPM’s and high carbon deposits are associated with short trip driving where the vehicle engine is not allowed to fully warm to normal engine operating temperatures. Cold ambient temperatures will increase engine warm-up time and add to the opportunity of carbon deposit build-up on the stem of the engine exhaust valve.
Date: 08/01/03
Model Year(s): 1999-2004
Description: NOTE: THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH A 4.0L ENGINE. This bulletin involves inspection of all engine exhaust valves and a decarbonizing procedure if necessary.
Details: The customer may experience an incident of engine misfire during certain vehicle operating conditions. The misfire may occur when the vehicle is operated between 50 - 70 MPH and under light loading conditions, e.g. slight uphill road grades. This condition may occur at all ambient conditions, but is more noticeable when ambient conditions are less than 0 C (32 F).
If the vehicle is equipped with On-Board Diagnostic (OBD), a MIL illumination may also have occurred due to Diagnostic Trouble Code (DTC) P0300 - Multiple Cylinder Misfire. Various single cylinder misfire DTC’s may also be present. If the frequency of misfire is high the Powertrain Control Module (PCM) may place the engine in “Limp-In” mode.
The misfire condition may be caused by one or more engine exhaust valves that are slow to close. Late closure of an exhaust valve may be the result of no valve rotation and associated build up of carbon on the exhaust valve stem.
This condition may occur when the engine is not allowed to run at engine RPM’s that are greater than 3,200 RPM. At 3,200 RPM or higher the engine exhaust valves will rotate if not impeded by high carbon deposits. Low engine RPM’s and high carbon deposits are associated with short trip driving where the vehicle engine is not allowed to fully warm to normal engine operating temperatures. Cold ambient temperatures will increase engine warm-up time and add to the opportunity of carbon deposit build-up on the stem of the engine exhaust valve.
Run the engine up to about 2K rpm and slowly dribble the water into the throttle body...enough to get it to sputter a bit, but no more.
Following that you may want to thoroughly warm up the engine and rev it up over 3,200 RPM a few times to rotate the exhaust valves. You may have to repeat both things a second time, depending.
Last edited by Radi; Nov 4, 2012 at 01:57 AM.
Junior Member
Joined: Oct 2012
Posts: 36
Likes: 0
From: Beverly Hills Fl.
Year: 01
Model: Grand Cherokee
Engine: 4.0
If the thought of dumping water into your engine bothers you, try sea foam. Follow the directions on the bottle, and if there is a lot of carbon in your engine, you will pump tons of white smoke out of your exhaust. I've seen it done, and have done it myself.
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Joined: Aug 2011
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From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Member
Joined: May 2009
Posts: 172
Likes: 2
From: CT
Year: 2001
Model: Cherokee
I'd check your injectors...I had a similar problem and it was due to a few of the injectors leaking internally...I ended up upgrading mine...but I believe they can be cleaned and tested for less money...
Thread Starter
Senior Member
Joined: Feb 2012
Posts: 627
Likes: 3
From: newjersey
Year: 2000
Model: Cherokee
Engine: I6
couple questions. how do you check if they are leaking? what did you upgrade to? and how much did it cost you?
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,577
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Senior Member
Joined: Aug 2011
Posts: 760
Likes: 6
From: Landers, CA
Year: Several
Model: Cherokee
Engine: 4.0
Not the coil rail, not the CPS, Seacrap, MMO, Water etc will not help.
Coil rail will not set codes, CPS very rarely sets codes.
Injectors don't swap positions.
You have the typical symptoms of an intake vacuum leak - -- very popular on inline Jeeps.
Engine off - Blow cigarette smoke through a vacuum hose into the intake manifold, rag in TB.
Fix wherever it comes out!
Best of all - IT'S FREE!
Let us know!
Pouring cold water or ANY liquid down is dangerous! Unless you really want your valve stems to look like Pretzels. -- hot stems, cold water == $$$$.
Or it can loosen a chunk of carbon, causing it to get stuck in a valve, holding it open so the piston can smack it and bend it, or it hitting the roof and knocking a hole in a piston.
I fired a guy for doing it after I told him not to! I witheld his pay to pay for the repairs and the customer's rental car. He sued me - he lost!
Coil rail will not set codes, CPS very rarely sets codes.
Injectors don't swap positions.
You have the typical symptoms of an intake vacuum leak - -- very popular on inline Jeeps.
Engine off - Blow cigarette smoke through a vacuum hose into the intake manifold, rag in TB.
Fix wherever it comes out!
Best of all - IT'S FREE!
Let us know!
Pouring cold water or ANY liquid down is dangerous! Unless you really want your valve stems to look like Pretzels. -- hot stems, cold water == $$$$.
Or it can loosen a chunk of carbon, causing it to get stuck in a valve, holding it open so the piston can smack it and bend it, or it hitting the roof and knocking a hole in a piston.
I fired a guy for doing it after I told him not to! I witheld his pay to pay for the repairs and the customer's rental car. He sued me - he lost!
Last edited by rrich; Nov 4, 2012 at 05:22 PM.