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96 Jeep won't idle in really cold weather.

Discussion in 'Repairs, Maintenance, Help' started by MarkT, Dec 28, 2017.

  1. MarkT

    MarkT Member

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    Looking for some help. My 1996 Jeep Grand Cherokee has 89k miles and a 4.0 liter gas engine. It won't idle in the very cold weather. Long story short it started this 2 years ago and was a little worse last winter but only in bitter cold. It was good this winter but now it's teens in the day and single digits at night.

    I have to keep my foot on the gas for it to run but this happens only in very prolonged cold like it is here now. Temps in the 20s and on no problem. A day or two of real cold no problem. Bitter sustained cold, problem!

    There is over 3/4 tank of gas. I keep it filled in the winter. I even put some dry gas in Saturday anticipating the cold. The battery is a 3 year old Interstate.

    I've read it could be an Idle Air Control Valve (Motor), a MAP sensor or a TPS sensor. I didn't get any codes. Any advice would be helpful since it's really cold out and I'm trying to limit time outside and next week will be colder yet.
     
  2. ImperialCrown

    Level III Supporter

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    Is the inside of the air cleaner getting motor oil and condensation build up? Is it soaking the paper air filter?
    The PCV valve on these was an orifice in a plastic line and could plug up easily sending blow-by into the air cleaner and causing both running/starting problems.
    I usually replace the line and don't try cleaning it. Replace the filter element if it got soiled. You should have good vacuum at the end that enters the valve cover.
    See items # 2 and # 3 here:
    00000DZ6.png
    Make sure that the throttle body bore and blade are clean and carbon free. Carbon build-up and moisture might invite icing.
     
    1999 White C5 Coupe likes this.
  3. MarkT

    MarkT Member

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    Just went out and looked. Dang it's cold out there. The air cleaner filter box is dry. The filter is a little dirty but all the pleats are dry. No oil or moisture. I pulled the large hose off the throttle body and looked inside. It actually looks good. The blade is shiny. I might wait till tomorrow and look at #2/#3 and #1/#4. It'll still be cold but least sunny and no wind like right now. I'll let you what i find in those.
     
  4. ImperialCrown

    Level III Supporter

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    If things are clean and dry, then the 'PCV' sounds like it is working OK.
    Are the spark plugs the correct Champion Copper Plus RC12LYC.
    This has the spark rail instead of distributor and wires, correct? Check and adjust the cam position sensor, if necessary:

    View: https://www.youtube.com/watch?v=eV7ase3dcoc
     
  5. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    Back around the Blizzard of 78, it was about -5F outside, and my carbureted 66 Plymouth began freezing up. It would not idle without my foot holding the gas. I drove 80 miles home from college, and even 70 miles into the trip with engine hot, it would stall when I coasted. Had to hold the throttle open the entire way. I suspect water is freezing in your fuel system somewhere.
     
  6. MarkT

    MarkT Member

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    I know the plugs are good since i changed them, the oil and the antifreeze this fall and I've used Champions all my life. This has a distributor and plug wires, not a spark rail. 4.0 liter 6 cylinder.The carbon inside the throttle body and plate is very light, not a heavy build up.
    I'm in northern PA. so we get winters. Average cold doesn't affect it, 20's-30's. Just prolonged bitter cold like now. It will start and idle in cold weather just in this bitter cold it will start but won't idle. I have to keep my foot on the gas or it will stall. It's been cold for a few months and was fine, just this very cold weather seems to affect the idle from working.
     
  7. ImperialCrown

    Level III Supporter

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    There should be a fuel pressure fitting on the fuel rail. 44-54 psi (305-370 kPa) should be the pressure. I would think that low fuel pressure would affect acceleration and hill-climbing when fuel demands are greater, than at idle when fuel demands are low.
    Most gasolines contain ethanol which absorbs some water. This gives some 'dry gas' capability to the fuel. 'Bad' gas from breeched storage tanks can still happen.
    A scan tool may tell you what the ECT (engine coolant temperature sensor) thinks the engine temperature is.
     
  8. MarkT

    MarkT Member

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    I took the pcv lines apart this morning. All clean and dry. I took the battery out last night and let it charge over night in the cellar. Put it in and started right up then stalled. It'll run with my foot on the gas but as soon a I take it off it'll stall and won't idle. Only seems to do this in very cold weather.
    I buy gas for all the vehicles at the same station. My car is fuel injected and the truck is carbureted. They both idled fine this morning even in this very cold weather.
    I did put in a bottle of Heet in last Saturday in anticipation of this bitter cold. Over 3/4 tank of gas. Ran great all along till this bitter cold, now it won't hold an idle.
     
  9. NYBo

    Level III Supporter

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    Check for vacuum leaks.
     
  10. MarkT

    MarkT Member

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    Went back out this afternoon with fresh batteries in the scan tool. It was a balmy 17, sunny and no wind. I charged the battery over night (a 3 year old interstate) and it fired right up and with a little coaxing i got it to idle. Scan tool came up with no codes. I disconnected the battery a few times and did the test a few times. No codes or faults. I did the dash keep dance and got no codes.

    The initial coolant temp showed 38 degrees with an outside air of 17, which it was. As it warmed up it read 195-196.

    I have it in the garage now. I believe (please correct me if I'm wrong) it may be a dirty idle air control motor which I'll clean in a warm garage tomorrow, or a vacuum leak in the ccv system. I ordered two grommets,two pcv elbows and the hose tube which I'll change in a warm garage next week.

    The only other thing i can think of (any additional input is appreciated) is the battery may be on it's way out. It's a 5 year interstate installed 12-1-14.
    The post and terminals are all very clean. The lights are bright and the dash gauge shows no discharge.

    Any additional ideas or advice is appreciated.
     
  11. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    See my post above.
     
  12. MarkT

    MarkT Member

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    Hi Bob,

    I had it in the garage last night. I'm going to fill the tank again today and toss in another bottle of Heet. If there is water in the fuel i don't know what else to do right now to get it out. The reason i'm a little skeptical is all the other vehicles (all Mopars) don't have this problem and are outside. I'm a creature of habit. They all get Prestone anti freeze, Valvoline oil, Fram filters, Champion plugs. I buy the gas for all of them at the same station. It's on a hill so water never ponds in the lot from rain.
     
  13. Rickorino

    Rickorino Well-Known Member

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    Very doubtful water is the problem. There is up to 10 percent alcohol in the gas already which is basically the ingredient in the Heat product. I would check fuel pressure, the IAC which could have a carboned up pintle or bore, it is responsible for your idle speed. If all check out I would look at fuel trims with a scan tool, your readings will tell you a lot as far as the fuel mixture and look why your ECT is a little off. It should be a little closer to your outside temperature and could be adding to your difficulties without tripping a code.
     
    Doug D and ImperialCrown like this.
  14. ImperialCrown

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    Agree. If you already have E10 gasoline in your area, you don't really want to add any more alcohol to the fuel than that. Diagnose first.
    If you introduce a vacuum leak to the intake manifold (which is basically what the IAC does to control idle speed), does the idle speed come up and keep the engine running then?
    Check the 'no trouble code' tests in the Powertrain Diagnostic Procedures book beginning on p. 218 here:
    http://oskin.ru/pub/chrysler-dodge/manuals/Service Manuals/2002_WG_Jeep_Grand_Cherokee/02wgep.pdf
    Evaporative emissions faults usually don't cause driveability issues unless things are grossly rich, like from the vapor system being flooded with raw fuel. Plug tips may be black with carbon. Otherwise, disregard this test.
    The SKIM key (if equipped) has to be OK if it runs by feathering the gas pedal off-idle and the dash SKIM/VTS warning lamp is out. Disregard this test.
    The radiator/hydraulic fan probably has little to do with idle quality. Disregard this test.
    The start/stall condition test is on p. 269 and has some bearing on what may be happening here.
    Connector pinouts and simple wiring diagrams are in the back of the manual. There is a PDP manual for the 1996, but not for free online. There may be differences.
     
  15. MarkT

    MarkT Member

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    WOW. I certainly appreciate the information and feedback. Just an update since this may help other people also. I filled the tank yesterday and added half a bottle of Heet. I don't really like loading up on dry gas. I left it sit outside last night but put the battery in the cellar. It was put in 7-1-14 so it's 3 1/2 years tomorrow. It started and with a very slight throttle effort it idled.

    I messed up the ECT test last time. Today i got an initial reading of 15 degrees with an outside air temp. of 9 degrees and the coolant temp started going up a degree every few seconds. The last time i got 38 with 17 outside air but i did the code test first not realizing the coolant was warming, duh.

    It fired right up after that as i used it today. I pulled two plugs and they're clean. The engine overall is pretty solid and tight.

    I have the ccv parts order since when i checked the hoses the other day they were clear but pretty old and dry so those will be changed. I'm going to clean the IAC motor also since that's easy to get at. I will also check the fuel pressure since there is a long rough winter ahead.

    The Jeep doesn't have a SKIM key. Don't know what VTS stands for? I took the oil fill cap off and looked in the valve cover. Very clean, no muck or moisture. I appreciate the manual. I'm going to read that over and I'll post results afterwards since it may help others with a similar problem but tomorrow i have busy day of laying on the couch and watching college football.
     
  16. chuzz

    chuzz Well-Known Member

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    Are those the original plug wires? If so, one or more may be breaking down due to the cold. I'd try replacing them, if nothing else works. Pull the plugs, like IC suggested and look at them.
     
  17. valiant67

    valiant67 Rich Corinthian Leather
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    VTS is the factory security system. You can have the security system even if you don't have the SKIM key.
     
  18. Muther

    Muther Well-Known Member

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    I am a battery expert. I am not a car expert.

    A sealed (recombinant) lead-acid battery like the one you have is pretty much guaranteed to last 3 years. Usually they last 5 years. I’d replace your battery just in case.

    Measure voltage at the battery when your symptoms are occurring. A low battery voltage MAY be the cause. If the battery has failed, this “could” be casing your symptoms.

    Batteries are sensitive to cold. Colder temps means a battery that is less reactive, and therefore has less energy to deliver. A battery that is warmer is MORE reactive, and therefore it has MORE energy to deliver.

    Again, I don’t think that this is your problem, but stranger things have happened.

    Most folks wait until the battery won’t start the car before they replace it. At that point it already failed, and because it’s start voltage drops so low before the alternator/Charger comes up, this scenario causes stress on your electronics.

    I replace my batteries at three/four years whether they need it or not.

    Again, this don’t know jack smack about cars like these guys do. I am sure they will weigh in (they are brilliant). However, I know more about batteries than anyone on these boards.

    Good luck, I enjoy reading no these problem threads. To a guy like me, they are better reading than a good novel. Please post up the fix once you have it, because if you don’t, we won’t know how the story ends.
     
  19. MarkT

    MarkT Member

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    I appreciate the feedback. The Jeep doesn't have an anti-theft system. Just an old fashioned key. I bought it used years ago. Loaded with options but no theft system. I pulled two plugs out of it yesterday and they were clean. The wires aren't new but not original. I'm going to put it in the back of the garage tonight and take the under hood bulb out. I know if wires are breaking down you can see arcing if it's really dark enough when it's running.

    The battery may be on it's way out but i don't think that is affecting the idle issue when first starting. I'm going to change the pcv parts when they come in this week, clean the Idle Air Control Motor and test the fuel pressure. Those are both original and i don't think the motor was ever cleaned. With 89k miles it can't hurt.

    I checked the battery voltage with the scan tool while running and it was good. The charging system is good but I'm not ruling out the battery, just fixing what looks like two issues first. Changing the old pcv parts and cleaning the IAC motor. I'm not a car guy in the sense that i ever took a class or did it for a living. I managed to learn some things over the years out of necessity.

    I'll post the results since i also want to see how this novel ends, but first a very rare day of doing nothing but watching college football.
     
  20. chuzz

    chuzz Well-Known Member

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    The best way to see if the plug wires are leaking is to get a spray bottle of water and with the engine running (in the dark) spray the wires. You'll see all kinds of dancing sparks if they're leaking.
     
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