1. Welcome to Jeeps.net!

    You are currently viewing as a guest! To get full-access, you need to register for a FREE account.

    As a registered member, you’ll be able to:
    • Participate in all Jeep discussion topics
    • Transfer over your build thread from a different forum to this one
    • Communicate privately with other Jeep owners from around the world
    • Post your own photos in our Members Gallery
    • Access all special features of the site

Hard start with rough idle and miss at road speed

Discussion in 'Cherokee' started by scovik88, Sep 10, 2019.

  1. Sep 10, 2019 at 8:25 AM
    #1
    scovik88

    scovik88 [OP] Member

    Joined:
    Sep 10, 2019
    Member:
    #3799
    Messages:
    9
    Gender:
    Male
    Vehicle:
    97 Grand Cherokee Laredo 4.0
    Hi Folks and thanks for the add to the group. I got a great deal on my 97 Grand Cherokee and it been great so far. But the past few months it has been taking more cranks to start and I have to turn off the key and crank it again b4 it starts.So I figured I would change the plugs ( gapped at .35) and wires and distr. and rotor. Now it's still hard to start and now I have a rough idle and a slight miss goin down the road. I have 170,000 mile on it. What should I check next? Thanks for the help.
     
  2. Sep 10, 2019 at 9:09 AM
    #2
    Prerunner1982

    Prerunner1982 Well-Known Member

    Joined:
    Aug 4, 2017
    Member:
    #1745
    Messages:
    957
    Gender:
    Male
    First Name:
    Jon
    Vehicle:
    93 XJ 2 door, 97 XJ 4 door, 00 XJ 4 door
    Do you have any Check Engine codes? If so, post them up.
    I would also check fuel pressure, the multiple cranks to start is sometimes a sign that the fuel is draining back into the tank. Low fuel pressure might cause the rough idle/miss.
     
  3. Sep 10, 2019 at 9:19 AM
    #3
    scovik88

    scovik88 [OP] Member

    Joined:
    Sep 10, 2019
    Member:
    #3799
    Messages:
    9
    Gender:
    Male
    Vehicle:
    97 Grand Cherokee Laredo 4.0
    No, no codes at all. I will check the fuel pressure. I hope it's not the fuel pump . Thanks for the reply.
     
  4. Sep 10, 2019 at 9:20 AM
    #4
    aggrex

    aggrex Well-Known Member

    Joined:
    Sep 12, 2016
    Member:
    #203
    Messages:
    2,968
    DE
    Vehicle:
    Backcountry '16
    Tuffy>AEV>TTO>JW>STech>EVOcage>MagnaFlow>SpiderTrax>RockHard>TF>SpringTail>67design>Bolt>GPCA>Curt>
    Welcome @scovik88 ...just to eliminate a variable have the battery/alt checked out free at places like advance auto. They will also check for any CEL.
     
  5. Sep 10, 2019 at 9:28 AM
    #5
    Awrench

    Awrench Well-Known Member

    Joined:
    May 12, 2018
    Member:
    #2303
    Messages:
    699
    Gender:
    Male
    Vehicle:
    3 jeeps
    welcome to the forum..

    hope we can help, you mention NO CODES - will your scanner display live data?
    Would be nice to look at ECT, TPS, MAP, fuel trims and o2 sensor voltages. That will give us the big picture.

    For fuel pressure -- attach gauge, turn key to RUN observe and record high pressure at @3 seconds, then leave key in RUN post the pressure in 5minutes -

    Plugs yeah it matters, a simple solid core is best, champions or NGK.
     
  6. Sep 10, 2019 at 3:12 PM
    #6
    scovik88

    scovik88 [OP] Member

    Joined:
    Sep 10, 2019
    Member:
    #3799
    Messages:
    9
    Gender:
    Male
    Vehicle:
    97 Grand Cherokee Laredo 4.0
    I put in the Champion. Seemed to be the popular choice here. And I will need to get to the auto parts store and get the other things checked and pick me up a fuel pressure gauge. I will post again after I do. Thanks for all the suggestions. I have to figure it out soon cause it's getting harder to start.
     
  7. Sep 10, 2019 at 3:48 PM
    #7
    aggrex

    aggrex Well-Known Member

    Joined:
    Sep 12, 2016
    Member:
    #203
    Messages:
    2,968
    DE
    Vehicle:
    Backcountry '16
    Tuffy>AEV>TTO>JW>STech>EVOcage>MagnaFlow>SpiderTrax>RockHard>TF>SpringTail>67design>Bolt>GPCA>Curt>
    Since the rough idle+slight miss seemed to occur AFTER the plugs+wire+dist+rotor, confirm wires are installed + routed correctly to avoid any chance of arcing or damage from hot or sharp surfaces.
     
  8. Sep 11, 2019 at 1:39 AM
    #8
    scovik88

    scovik88 [OP] Member

    Joined:
    Sep 10, 2019
    Member:
    #3799
    Messages:
    9
    Gender:
    Male
    Vehicle:
    97 Grand Cherokee Laredo 4.0
    Well I actually replaced the wires last. I had the plugs from about a year ago and replaced them first and the rough idle started then. I then got the new dist. cap and rotor button, still no change and then replaced the wires. With my memory not being what it used to I replaced them one at a time to be sure I put them back the way they came out and them rechecked them to make sure they were all spaced right. I also made sure the new plugs were tight. But I might pull them back out to recheck them also.
     
  9. Sep 11, 2019 at 1:43 AM
    #9
    scovik88

    scovik88 [OP] Member

    Joined:
    Sep 10, 2019
    Member:
    #3799
    Messages:
    9
    Gender:
    Male
    Vehicle:
    97 Grand Cherokee Laredo 4.0
    Another thing is that I've had the hard start problem for about six months. It just seemed to get worse over time and it would usually take two long cranks to start. Well yesterday it started to take me three long cranks before it would start. So I'm gonna check for codes and get a number on my fuel pressure and see where I'm at. But the deeper I get into it the more I think it's the fuel pump. Thanks all
     
  10. Sep 11, 2019 at 8:06 PM
    #10
    JKBob 25

    JKBob 25 Well-Known Member

    Joined:
    Mar 22, 2017
    Member:
    #1197
    Messages:
    3,535
    Gender:
    Male
    First Name:
    Bob
    Jersey Shore, NJ
    Vehicle:
    2016 JK Wrangler Sport
    2" Superlift kit. 315/ 70/17.
    Welcome @scovik88 . My GFs 98 had a similar issue. We replaced cap, condenser, and wires. Still a problem. Shot in the dark. We replaced the coil. Bam....issue fixed. For $25. Worth a shot.
     
    aggrex likes this.
  11. Sep 12, 2019 at 1:28 AM
    #11
    scovik88

    scovik88 [OP] Member

    Joined:
    Sep 10, 2019
    Member:
    #3799
    Messages:
    9
    Gender:
    Male
    Vehicle:
    97 Grand Cherokee Laredo 4.0
    ...and easier to get to than the fuel pump. I'm gonna start testing everything today. Thanks, by the way did her Jeep also have rough idle to go along with the hard start before you changed out the coil? Thanks again for the help.
     
    Last edited: Sep 12, 2019
    JKBob 25 likes this.
  12. Sep 12, 2019 at 3:20 AM
    #12
    Awrench

    Awrench Well-Known Member

    Joined:
    May 12, 2018
    Member:
    #2303
    Messages:
    699
    Gender:
    Male
    Vehicle:
    3 jeeps
    at part store, get the fuel pressure gauge - loaner, rental or purchase...and 1 can 'seafoam' for gas tank also a can of carb cleaner and look at this video - is easier/better than explaining... what do they say a picture =1000 words so a video speaks tomes
     
    JKBob 25 likes this.
  13. Sep 12, 2019 at 3:26 AM
    #13
    scovik88

    scovik88 [OP] Member

    Joined:
    Sep 10, 2019
    Member:
    #3799
    Messages:
    9
    Gender:
    Male
    Vehicle:
    97 Grand Cherokee Laredo 4.0
    Thanks Awrench, will do. But I wasnt able to open/see the video.
     
  14. Sep 12, 2019 at 3:46 AM
    #14
    Awrench

    Awrench Well-Known Member

    Joined:
    May 12, 2018
    Member:
    #2303
    Messages:
    699
    Gender:
    Male
    Vehicle:
    3 jeeps
    JKBob 25 likes this.
  15. Sep 12, 2019 at 4:42 AM
    #15
    scovik88

    scovik88 [OP] Member

    Joined:
    Sep 10, 2019
    Member:
    #3799
    Messages:
    9
    Gender:
    Male
    Vehicle:
    97 Grand Cherokee Laredo 4.0
    Yes it does. But we ain't gonna go down without a fight. Lol, thanks
     
  16. Sep 13, 2019 at 6:59 PM
    #16
    JKBob 25

    JKBob 25 Well-Known Member

    Joined:
    Mar 22, 2017
    Member:
    #1197
    Messages:
    3,535
    Gender:
    Male
    First Name:
    Bob
    Jersey Shore, NJ
    Vehicle:
    2016 JK Wrangler Sport
    2" Superlift kit. 315/ 70/17.
  17. Sep 13, 2019 at 7:00 PM
    #17
    JKBob 25

    JKBob 25 Well-Known Member

    Joined:
    Mar 22, 2017
    Member:
    #1197
    Messages:
    3,535
    Gender:
    Male
    First Name:
    Bob
    Jersey Shore, NJ
    Vehicle:
    2016 JK Wrangler Sport
    2" Superlift kit. 315/ 70/17.
    Honestly...IDK...I just got a call her ZJ died. But the coil was the issue. And it didn't happen again.
     
  18. Sep 18, 2019 at 5:10 PM
    #18
    scovik88

    scovik88 [OP] Member

    Joined:
    Sep 10, 2019
    Member:
    #3799
    Messages:
    9
    Gender:
    Male
    Vehicle:
    97 Grand Cherokee Laredo 4.0
    Ok I'm back....long week. I got to test my fuel pressure from the pump. I got 40 psi when I had the key in the on position and it fell to zero psi when I switched the key off in about 10-12 seconds. When I turned it over and when it was started it held 40 psi also but also dropped to zero psi in 10-12 seconds.
    So from what I've read I think the pressure is good on the pump. I'm wondering why it drops so quick and I still have to check the coil. Thanks for any help or tips.
     
To Top