98 grand cherokee cyliner 1 misfire,, HELP ..

po300 is a random misfire, a P0300 doesn't tell you specifically which cylinder(s) is/are mis-firing, nor why. If it was a po302 this means its #2 cylinder thats misfiring,ETC, But po300 could be any one of the cylinders. check plugs, wires, fuel injectors, Etc. Good-Day!

have them check the fuel injectors and comprission test the engine ask the genral mgr what kinda techs he has that cant find a mis fire

300 is random misfire and 306 is cylinder #6, I would check the coil pack on #6. If it has separate coils per cyliner, swap the coil, see if the misfire goes to that cylinder. If it does replace the coil.
If it has three coil packs you can still swap the coils. If that doesn't fix your problem, then you will have to check the injector with an ohm meter. resistance between the prongs should be between 11 to 15 ohms. check another injector and they should be relatively close. Let me know
Good luck

Yes, it would. But not the whole pack, just the coil for that cylinder would be the problem. Try swapping them around and see if the mis-fire follows the suspect coil.

For the 1998 Jeep Grand Cherokee Laredo:
I do not know if you have the 4.0L In-Line 6-Cylinder, the 5.2L V8, or the 5.9L V8; however I have included ALL below:

For the 4.0L In-Line 6-Cylinder:
Firing Order:
1-5-3-6-2-4
Cylinders:
(back)
...6
...5
...4
...3
...2
...1
(front)

Distributor:
....(back)
.....5....3..(+)-screw
1.............6
(+).4....2

For the 5.2L V8: AND 5.9L V8:
Firing Order:
1-8-4-3-6-5-7-2
Cylinders:
.......(back).......
|..8..|.........|..7..|
|..6..|.........|..5..|
|..4..|.........|..3..|
|..2..|.........|..1..|
.......(front)
Distributor:
.....(back)
.......3
..4.........6
8.............5
..1.........7
.......2
......(front)

Let me know if this helped, or if you have additional information or questions. Feel Free to contact me at FixYa.com!

For the 1997 Jeep Grand Cherokee:
I do not know if you have the 4.0L In-Line 6-Cylinder or the 5.2L V8, however I have included both below:

For the 4.0L In-Line 6-Cylinder:
Firing Order:
1-5-3-6-2-4
Cylinders:
(back)
...6
...5
...4
...3
...2
...1
(front)

Distributor:
....(back)
.....5....3..(+)-screw
1.............6
(+).4....2

For the 5.2L V8: (Side Note 5.9L V8 = Same)
Firing Order:
1-8-4-3-6-5-7-2
Cylinders:
.......(back).......
|..8..|.........|..7..|
|..6..|.........|..5..|
|..4..|.........|..3..|
|..2..|.........|..1..|
.......(front)
Distributor:
.....(back)
.........3
....4........6..(+)-rounded tab screw
8................5
[ ].1.........7
.........2
......(front)

Let me know if this helped, or if you have additional information or questions. Feel Free to contact me at FixYa.com!

Fuel injector cleaner commonly has a low success rate, and will not help if it's more than one cylinder that is missfiring. The fact that you have a "rattle" noise, leads me to beleive the engine is not receiving fuel on one or more cylidners. If it is all the cylinders, than the fuel pump may be the culprit, or the fuel pump circuit. But if only one cylidner is missfiring than it is a possibly an injector. A code P0300 refers to all cylinder missfires, and any code between P0301-P0308 distinugiushes a particular cylinder.

Misfiring
1- a general electrical tune-up (spark plugs, wire set, cap & rotor) is a basic start to cure this issue. Wiggle the dist shaft while you are in there, if you have one.
2- Then a good carbon cleaning / throttle-body cleaning.
3- Vacuum leaks at any of the hoses that connect to the Intake manifold; especially the MAP sensor connection.
4- If that does not help then the O2 sensor could be bad or drifting.
5- Funky coil/coil-packs
6- Theoretically a microsecond glitch in either the cam or crank shaft sensors would cause this, but I am not aware of this as a typical cause.
7- Lastly a funky PCM but again it is not common for this to cause miss-firing.

Note for the V8 then also:
a) bad erg valve (this dilutes the combustion gases and hence raises the combustion temp
b) a leaky plenum/Intake manifold gasket. Leaking Intake gasket symptoms

Also can check the TSB 18-48-98 Ignition System Cross Fire/Secondary Ignition Wire Induction (Complete Version )

Hope help with this (remember rated this). Good luck and have a nice day.

You could try an additive to go in your fueltank, in England its called Redex or STP, that may help as they are designed to brake down the carbon build up

1.Plugs
2. Vacuum leak
3. Injector fault
4. High or low fuel pressure.
Thats the list of things to check.
This is a #3 cylinder misfire.
There is also TSB about #3 injector needing added heat protection. This could definitely be the cause. I start at plugs and go from there.
Hope this helps.
Thank you,
Lee

I wrote all engine spec for a 2005 jeep grand cherokee

3.7L 6 cylinder
1-6-5-4-3-2

4.7L 8 Cylinder
1-8-4-3-6-5-7-2

5.7L 8 Cylinder
1-8-4-3-6-5-7-2

let me know if this help you.....