Question about 1998 Jeep Cherokee

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Engine will idle but backfires thru the exhaust and air box

Just rebuilt the 4.0 put it in and started it up. let it idle to fill the rad. and when i tried to bring up RPM's it would bust out like intake AND exhaust valves were open. good compression on all cylinders replaced almost everything except flywheel and computer.......heeeeelp

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  • pikupmn Feb 09, 2009

    the timing order is correct but the #1 is the 2nd one from lower screw acording to my book. cap& rotor are good. it runs fine at idle just backfires at acceleration ,

  • pikupmn Feb 09, 2009

    it idles fine just starts busting out at 1200+ RPM firing order is OK #1 is 2nd from lower screw according to my book(clockwise) cap&rotor are good

  • pikupmn Feb 09, 2009

    thanx, T-god will try that.............pc302001 , you cant adjust the timing it is set by the PCM

  • pikupmn Feb 10, 2009

    1st.... thanx to every1 for the help, put scanner on jeep and it said the sync was off, turned distributor cam gear one tooth clockwise and solved the problem.....thanx again

  • Barry N Melissa Spring
    Barry N Melissa Spring May 11, 2010

    Correct timing order?



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How about adjusting the timing.

Posted on Feb 09, 2009

  • Barry N Melissa Spring
    Barry N Melissa Spring Feb 09, 2009

    Was dealing with my problem when I came across yours. Wasn't thinking fully about PCMs. Hope "GURU" solved it for ya. Please post if that helped. I'd like to know. Good Luck!

  • Barry N Melissa Spring
    Barry N Melissa Spring Feb 11, 2009



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Are you certain that you have the ignition wires hooked up to the correct cylinders(153624 from front of engine back, #1 on cap 1st post past the lower cap screw, clockwise) That's the only thing I can think of that will give you misfire in both intake & exhaust. Cap & rotor are new?

Posted on Feb 09, 2009

  • Richard Scordino Feb 09, 2009

    OOPS... That's what happens when I attempt thinking before 1st cup of coffee!!! Second tower cw from screw on right side.Lets boil it down... If valves were open at wrong time, cam would need to be out or phase.(possible) If valves were open because they were not closing, lifters would need to be "pumped up" too much and acting like solids. Or, too much material had been milled from head. Since they are hydraulic, that is so unlikely as to be a non issue. Unless oil pressure is something like 100!! Either way, a valve sealing problem would give you a rough idle and if checked with vacuum gauge, a rapidly fluctuating reading.It's nearly impossible to put the injector harness on wrong (you'd really have to work at that) You can't do anything to the crank or pistons to cause this.
    The distributor (and cap/wires etc) are only going to do what the cam is telling them to do. if the cam is incorrectly installed, spark will happen in relation to that position. OK, I've mentioned cam position twice. I have seen an incorrectly installed cam give fairly normal idle, incredible low end torque and major misfire on acceleration. ( a long time ago... If I remember correctly it was in one tooth retarded) I'm not sure you can accurately check this without real teardown. Possibly with dial indicator on rockers and piston (carefully through plug hole) you may be able to check it.But backside of lobe ramps is pretty wide and may cause innacuracy unless centerline is established. Therefore, if after a careful check of everything outside, you come up empty, remove the timing cover and check that cam is in correctly.



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2006 jeep Cherokee 5.4 hemi smokes real bad and idles rough but not when revving the engine

Have you had the engine control unit scanned for fault codes? Is this oil smoke or fuel?

Oct 20, 2016 | Jeep Cherokee Cars & Trucks

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Fans not turning on and replaced the coolant temp sensor? Coolant in reserve but not in radiator?

why do you have ? on facts? odd that.
my guess replaced ECT ! not ?
my guess, doing so , now engine is full of air, and not fails.
as all do.
front RAD cooling FANS, right? (not heater blower )
it don't work like you think, ? huh?
what does" not in Rad "mean? with ? marks?

means you trust the silly side tank and not look in rad? fail you will.
when doing cooling service, learn read a book first.
read how to fill and burp your engine, Just like feeding a baby it is.
is engine overheating?
did it , has it, or ? , what started this saga, tell a full story?
and WIN !
Facts: on this system.
the fans are controlled by the computer brain, under a complex set rules now. it's not some mindless switch like days of old.
ill now answer for USA 03, how ours work,
ours has one fan., (not fans)
ours has a 3 speed fan (at rad back side.)
and has rules to run all 3 speeds, via 3 relays
the PCM/ECU decides this, based on if A/C is on or off.
and a complex set of rules (uses the ECT for this magic)
Fact 2: ECT will not work with air pockets !!!!
The PCM even turns on and turn off are not same temp!!!
1: Rad must be filled of AF/ 50% antifreeze cold, to the top neck of RAD filler.
2: rad and engine burped of all air pockets, ask it's same on all cars.
3: the ECT must work, right, if air pockets there, it CANT work.
4: park car, idle until the minimum engine time is reached parked.
about 180F, but all cars overheat if parked, idling and fan stays dead.
fan is off , and at some point, the fan goes to low speed.

this varies by engine option, but is around 225F. (stage1)
THE FSM covers these checks, and rules, and temps. for all 3 stages of fan speed.
scan the pcm yet>?
got P0128 DTC? or others, for temperatures wrong,
not scanning is a big mistake on all modern cars.
big time!
yes, rad must be full parked cold, yes, yes, yes...
side expansion tanks do fail. for many reasons. ask.

a 2.0L engine. only, here. 7.4quarts cooling cap.
here is ours. usa fan. a 4 wire fan it is....
the ecu controls it using SOFTWARE, (firm-ware in truth)
26098393-rlcj0qgtvzvpudyok3p1nj5o-4-0.jpg do not drive car until all air is burped out of engine and rad.
in fact run it idling to hot. 180f. ( too hot to touch long)
, kill engine with key.
let cool, to luke warm, or cold.
check rad level. (sure its low)
top it off, cap it,
repeat 3 times, before driving or if it holds levels.

Feb 17, 2016 | 2003 Suzuki Aerio

2 Answers

Idles ok backfires thru exhaust under a load

Since it is so old, Start with a compression test. 90lbs is about minimal. The cylinders should be with in 10% of each other. If your there or lower, Time to retire or rebuild this engine. This part here will save you time, trouble and money into an engine that won't be any better when your done.

Feb 08, 2016 | 1987 Ford F 150

2 Answers

We changed thermostat sensor and thermostat, still over heating. What could it be?

overheating has many symptoms, not just green on the ground
do tell?

temp gauge lies its buns off... use a real tool called a thermometer to see real temps. we use a IR pyro gun to see it and not GET burnt.

gauges is telling truth, so......................

a bad rad cap, or bad thermostat are common fails.
test one: (dead cold engine) never hot.
radiator tank filler cap off , you look down there, is the level really low?
(forget the silly side expansion tank for now)
if found low , then fill it and burp it. no air allowed there
running 50% antifreeze now? no?, that its WRONG.
the tool is $2, test it. (Prestone sells it)
the coolant is all rusty color, (ill not comment ) try service.

  1. Green on the ground,? for passengers feet.
  2. Water exploding from overfill side tank? ( oil in RAD or Milky engine oil) (same milk in transmission pan?)Exploding gases, on cold start is bad head gasket or warped head or cracked head/block, or just simple overheating, The Rad leak down test and the exhaust test (green/blue ) tests solve this riddle easy.
  3. Steam rising from hood or Radcap, or hose to Cap and recovery tank. Over heating or leaks.
  4. Dash gauge pegged. (or WILD GAUGE swings "air pockets below thermostat") or gauge bad. sender bad.
  5. Motor pinging and loss of power. (do not allow pinging, it will wreck the engine)
  6. Pistons landing on ground? (just joking....)
  7. A/C dies?, does it?, due to A/C engine overheat switch ,tripping off. a 235 ?F (spec) see FSM. A/C means Air conditioner clutch dead.
  8. Does the engine over heat , if left idling a long time (30min-1hr). or only at stop signs or red lights? (clutch fan not activating , check it, this way.)
  9. Does it only over heat while moving ? ( a bad pump, or Rad)
  10. Overheats, only on hills? (bad RAD)
  11. Only overheats pulling heavy loads ? (inside, full of bricks, or pulling a 1000 trailer ? ONLY?
  12. Never overheats moving fast on flat ground. (so the RAD fan is dead, no mater if stock or hacked in electric fan, it's DEAD)
  13. Do you have carbon or oil floating around in the Rad, filler CAP neck top tank ? yes?, that is bad head gasket or worse cracked block/head. Do the Exhaust test.
  14. Overheats under all conditions, Catastrophic overheat. ( can be bad pump (rotor gone) or RAD or system is packed up)
  15. Seems to overheat , even at first start , in 1min or less I have gases shooting into the overfill tank, that is a bad head gasket (mostly a warped head, at least)
  16. Antifreeze (and water) in the pans, Engine or Transmission.
  17. The RAD fan is DEAD ( just because a mechanical RAD fan coasts, don't mean it WORKS RIGHT.) See the clutch tests below. if electric fan , there is a test in the FSM covers this 100% the fan must come on over heated,.
  18. my electric fan , starts to run idling engine long time at 225F. It kicks on, some cars have 2 fan and staged, come on trip points.
  19. RTM read the manual the FSM>
  20. there is more im sure, cant think of them all now.

That pyro gun allows me to test any RAD easy , ask.
ok , i check all rad tube top and bottom and bingo find any tube clogged fast. if all are equally clogged.(partial) i cant find that.
that is caused by zero service, so...and there are signs for that too.

Jul 02, 2014 | Cars & Trucks

1 Answer

Draining radiator

Terrific question!
First, fill the radiator with coolant, do not fill to the top, just fill about halfway up in the tank.
Start the engine and turn on the heater full blast.
Probably would be good to give it some gas to about a medium idle and hold it there, might require 2 people.
Very carefully watch the level in the tank.
DO NOT put your face over the hole. When the thermostat opens , the coolant will drop quickly.
Try to keep adding coolant as that happens.
After about 5 minutes you should be ready to go.
The way you will know is the heater is blowing hot air.
Now fill it up and replace our cap.
Be Blessed.

Feb 04, 2013 | Cars & Trucks

1 Answer

I have a 99 ford expedition eddie bauer. The heater works great sometimes and other times blows cold. If you turn it off and wait a few seconds and start it again it will work. Truck never over heats or...

You probably have air in the cooling system. These vehicles are sort of hard to bleed it out. I would recommend taking it to a dealership. Or you could take the rad cap off and run it but you will need a large funnel, one that is tight when going into the fill hole on the rad. Warm engine up, the fluid will rise a lot and this is normal. Once the engine is at operating temperature and the thermostat has opened up (grab upper rad hose it will be hot) rev it to 2500 rpm for about 10 seconds then release the gas pedal. This will help get the air out you will see bubbles in the funnel. Do that a few times (4 or 5) then leave it idle for a bit, put the hot air on through the vents it should stay hot if it is then you can put the rad cap back on if it doesn't stay hot you still have air in the system. I do it somewhat like this except I built a special rad cap specifically for the explorers.

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I have a 2005 dodge caravan with a 3.3 engine i have filled the radiator full let vehicle idle for 1 hour checked rad level and it has leaks nor over heating problems where is the anti freeze...

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if you have an LZ9 it will not have air bleed screws
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now if you have no bleeders
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then let the vehicle idle for 3 min
then shut the vehicle off and cool down so the rad cap can be removed
top up coolant
also make sure there is good hot air coming out of the heater if not repeat procedure there is still air in the cooling system
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