Misfire not fixed with plugs and coils. :(

[HerronScott]

All,

OK, a little concerned about 2002 Jeep Liberty. We were getting cylinder 4 misfires so I replaced all plugs and coils yesterday. I had done some troubleshooting and moving the coil did not change the misfire but changing the plug appeared to initially eliminate the misfire and since I had already purchased the coils, I went ahead and replaced them as well. Plugs did not look bad all around. Gap and color appeared pretty good but number 4 had some oil on the back of the ground electrode which concerned me a little but I took a test drive up and down the local bypass (about 10-15 miles) and all seemed good (cleared the CEL before the test drive).

We got in the Jeep today and the misfire and flashing CEL were back right after starting it in the driveway. Also, when my wife backed the Jeep out of the driveway it was blowing a little blue smoke which we had not seen before. We bought the Jeep back in February and have put about 7,000 miles on it this year including a vacation trip down to Charleston and no major issues. Currently it has about 160,835 miles on it. It appeared to be a very well taken care of example when we bought it with no rust and a relatively clean engine compartment (not

Any expert thoughts on what could be the likely cause? With the oil and blue smoke is it more likely to be a valve guide issue since it seemed OK yesterday during my test drive and only exhibited issues this morning after sitting over night or is more likely a ring issue?

Thanks for any advice you can give us. Not looking forward to repair costs.

Scott

 

[Dave]

Thoughts,


Sometimes it takes several driving cycles to clear codes. (you didn't say what they were) Driving cycle is stone cold (sitting all night) to highway run at normal running temp for a few miles......repeated over several days.


you used only OEM coil-paks.


You used the NGK copper core plugs and gapped as stated on your emisions sticker on the front frame on top of the radiator under the hood.


Can't think of anything else at the moment. I am sure other more experienced members will chime in.


Dave

 

[LibertyTC]

Please answer Dave's questions as above!
A flashing Engine light means serious code- as in turn off the Jeep!
Was the code still a misfire #4 then?
I would pull the # 4 spark plug and let us have a look at it in a photo.
Also time to pull the valve cover as well as inspection time!
Any objectionable rocker noise?

 

[tjkj2002]

At this point the most useful test is a compression test.

Since you moved the coil before replacement and no change it's not the coil no matter the brand and if a new plug helped for a bit it sounds mechanical issue.

 

[HerronScott]

At this point the most useful test is a compression test.

Since you moved the coil before replacement and no change it's not the coil no matter the brand and if a new plug helped for a bit it sounds mechanical issue.

Thanks, that was my conclusion as well based on the symptoms and initial troubleshooting (and light blue smoke).

It did bug me that replacing the plug seemed to fix it given the condition of the plugs which did not appear to be that old based on condition, gap and electrode condition.

I dropped the vehicle at the shop to have it looked at early next week.

Scott

 

[HerronScott]

Sometimes it takes several driving cycles to clear codes. (you didn't say what they were) Driving cycle is stone cold (sitting all night) to highway run at normal running temp for a few miles......repeated over several days.

Dave,

Thanks for the response. I manually cleared the CEL with Torque so this wasn't a case of waiting for a drive cycle. And the code was the same as before which was misfire on cylinder 4.

you used only OEM coil-paks.

No, but given the CEL did not come back during the 25 minute test drive I don't have any reason to suspect the replacement is suspect (and the blue smoke is not good). However, if it does turn out to be that I'll be extremely ecstatic.

You used the NGK copper core plugs and gapped as stated on your emisions sticker on the front frame on top of the radiator under the hood.

Yes.

Scott

 

[HerronScott]

Was the code still a misfire #4 then??/QUOTE]

Yes, same code as before.

I would pull the # 4 spark plug and let us have a look at it in a photo.
Also time to pull the valve cover as well as inspection time!
Any objectionable rocker noise?

No obvious rocker noise.

Scott

 

[grmpyoman]

I don't know if this will help, but this happened to me also. Misfiring all the time put new plugs and replace some of the coils and it kept coming back. After I talk to my one of my good friends at work who is a shade tree mechanic, he asked me what grade of gas I was using. I said the cheap stuff. He told me absolutely no way will the Jeep engine run good on cheap gas. Use the high-octane 91 and after I did that this thing is really beautiful.

 

[JasonJ]

^ It's something to try.

I replied in more detail to grmpy's post on his own issue... but be aware that just moving to a higher octane fuel (not necessarily higher quality with different additive package) may just be masking the problem, if it does anything at all.

But if it does improve with that switch, it should give you a direction on where to go to fix it properly.

FWIW, my Jeep engine has run perfectly for the 7 years that I've owned it on "cheap gas"; meaning just regular unleaded 87 octane.

If this does anything at all to improve your situation Herron, start looking into options to decarbonize the engine. Might be excessive carbon build up stopping the valves from closing all the way, or causing pre-ignition and resultant misfires.

 

[GunnerSchenck]

He told me absolutely no way will the Jeep engine run good on cheap gas.

Pretty sure most, if not all, of the people on here use regular gas and many have favorably functioning vehicles.
There's a gas thread somewhere on here you can dug up to see what everyone on here uses....and they're all 87.
Including myself. And my engines never skipped a beat..well minus the few times I've flooded the coils with water, but not gas related.
Sounds like if you have to run 91 octane to get your car to run correctly, the gas isn't the problem.
Also. May not be severe enough for you to notice, but you're actually using your fuel faster using 91 octane. So not only are you paying more, it's not lasting as long. Double the less "bang" for your buck.

 

[tjkj2002]

Pretty sure most, if not all, of the people on here use regular gas and many have favorably functioning vehicles.
There's a gas thread somewhere on here you can dug up to see what everyone on here uses....and they're all 87.
Including myself. And my engines never skipped a beat..well minus the few times I've flooded the coils with water, but not gas related.
Sounds like if you have to run 91 octane to get your car to run correctly, the gas isn't the problem.
Also. May not be severe enough for you to notice, but you're actually using your fuel faster using 91 octane. So not only are you paying more, it's not lasting as long. Double the less "bang" for your buck.

Not everyone has the option of 87 octane "cheap gas",around here it's 85 octane which should never be used in a FI engine.We have to pay 40 cents more for 87 octane and almost a dollar more for 91 octane.

Oh and not sure about newer years but '02 KJ's it is recommended to run 89+ octane gas when towing,states it in the owners manual.

I must run 91+ octane gas in my KJ,high altitude and moving 2200+lbs more around at 6200'+ elevation the cheap stuff just will not work.Nothing wrong with my KJ and is running correctly.


And finally the statement about using more gas if using 91+ octane over 87 octane is not correct.If your engine only requires 87 octane and is in perfect running condition you should actually use less gas using 91+ octane,same goes for a very dirty air filter you should again use less gas on any vehicle made model year 1996+.

 

[GunnerSchenck]

Oh and not sure about newer years but '02 KJ's it is recommended to run 89+ octane gas when towing,states it in the owners manual.

And finally the statement about using more gas if using 91+ octane over 87 octane is not correct.If your engine only requires 87 octane and is in perfect running condition you should actually use less gas using 91+ octane,same goes for a very dirty air filter you should again use less gas on any vehicle made model year 1996+.

Mine states only 87, 89 when towing. 03

His engine is not in perfect running condition if he has a misfire issue when using 87. Which no other person is experiencing from using 87 octane gas.
The gas is not the problem, but a bandaid. A very temporary bandaid.

87 octane has a lower combustion rate or a "knocking" condition (pre-detonation) yes.
But with a vehicle experience pre or post combustion issues, do you think his spark is hitting on time to combust 91 octane? That it will burn all the gas being pumped into it?
Likely he has carbon problems and gunk in there, and pumping in high octane that will not properly combust is going to cost him more money for the same result.

That was what my statement was aimed at. Wasting money to mask his problem until he ends up with a bad motor.


I'd love nothing more than for him to post back a year from now and say my motor is in great shape and I haven't quit using 91 octane. But if he continues, that won't be the thing he's posting.

 

[tjkj2002]

Mine states only 87, 89 when towing. 03

His engine is not in perfect running condition if he has a misfire issue when using 87. Which no other person is experiencing from using 87 octane gas.
The gas is not the problem, but a bandaid. A very temporary bandaid.

87 octane has a lower combustion rate or knocking rate, yes.
But with a vehicle experience pre or post combustion issues, do you think his spark is hitting on time to combust 91 octane? That it will burn all the gas being pumped into it?
Likely he has carbon problems and gunk in there, and pumping in high octane that will not properly combust is going to cost him more money for the same result.

That was what my statement was aimed at. Wasting money to mask his problem until he ends up with a bad motor.


I'd love nothing more than for him to post back a year from now and say my motor is in great shape and I haven't quit using 91 octane. But if he continues, that won't be the thing he's posting.

It's really not wasting $$$ running premium gas,on average premium has more cleaners(and better cleaners) then regular and refined a little better since they have to or risk damaging $100K motors.

A few tanks of premium can actually clean the injectors better and top end,does nothing for carbon buildup inside the intake manifold or throttle body.

And finally since altitude was not stated and a host of other factors that may make premium a better choice for said driver.

 

[JasonJ]

It's really not wasting $$$ running premium gas,on average premium has more cleaners(and better cleaners) then regular and refined a little better since they have to or risk damaging $100K motors.

A few tanks of premium can actually clean the injectors better and top end,does nothing for carbon buildup inside the intake manifold or throttle body.

And finally since altitude was not stated and a host of other factors that may make premium a better choice for said driver.

It makes sense that you have to use higher octane, given your conditions and use of the KJ. I think that's a unique use case.

As to more cleaners, or a different add-pack to premium fuel, that depends. Depends on the brand of fuel, who refined it, for what season, and for what general geographic area as well.

At least with top tier fuels, most have the same additive package in regular 87, 89, and 91/93 octane. Some, but not all have a different add pack to premium though.

If that's the case, then you bet, running a tank or two of that once per year can certainly help keeps things clean and running proper.

Gunner's not wrong either though that if this "fixes" the OP's problem, and he isn't in a unique use case like you, tj, where he's hauling a lot of weight, at high altitude, etc... it's just masking the real issue.

 

[Leeann]

I had an '89 Nissan 240sx that ran perfectly on 87 octane gas (and that's what it called for).

Until, that is, the idiots in MD added ethanol to the gas (yes, I understand that ethanol in gas has been in the midwest for decades with no problems, but the additives they put in on the east coast + ethanol = poo for gas). At which time it started knocking on 87 octane and the emissions (which had been almost nil) went up. Switched to 89 octane and all my problems went away.

Gave it the good stuff now and again and always got better mileage from it - and it responded well to it, too.

 

[JasonJ]

I had an '89 Nissan 240sx that ran perfectly on 87 octane gas (and that's what it called for).

Until, that is, the idiots in MD added ethanol to the gas (yes, I understand that ethanol in gas has been in the midwest for decades with no problems, but the additives they put in on the east coast + ethanol = poo for gas). At which time it started knocking on 87 octane and the emissions (which had been almost nil) went up. Switched to 89 octane and all my problems went away.

Gave it the good stuff now and again and always got better mileage from it - and it responded well to it, too.

Nothing good comes from putting ethanol in gasoline. Hmm.. take corn out of the food supply... put it in fuel.. reducing the BTU/gallon, claim it's cleaner for the environment... nevermind the plants and factories to produce it are polluting themselves now.

Plus it really screws up small engines like lawnmowers, ATV's, even my motorcycle hates fuel with ethanol.

 

[Conundrum2006]

Some times it depends on the brand gas too. Had a old rabbit that hated shell 87 octane, ran fine on every other brand .
Jeeps I've never had be picky about where the fuel comes from.
However all the different seasonal blends who knows. You can still find real gasoline without ethanol but it's costly, like finding lead gasoline when I was a kid.

240sx was a fun car. Better than the 80s 300zed far as weight to power.


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[Leeann]

240sx was a fun car. Better than the 80s 300zed far as weight to power.

Sent from my iPhone using Tapatalk Pro

That thing was a blast, right up until it rotted out beneath me. You could turn it on the back wheel, cruised at 90 MPH with no complaints, steering wheel cruise buttons...

 

[HerronScott]

Problem turned out to be a blown head gasket (and apparently at the number 4 cylinder).

Scott

 

[ltd02]

Problem turned out to be a blown head gasket (and apparently at the number 4 cylinder).

What's your strategy now that you've found it?