Intermittent rough idle and engine cuts off at approx. 2800 RPM

[TopShapeCabby]

I need you input on issues the Liberty is having......

In the past, this would happen every 6 months but it happened everyday this week, at least once a day:
-start the Jeep, run rough (1 to 2 cylinders out)
-engine light blinks
-low power (obviously)
-as I drive, the engine cuts out every time I hit approx. 2800 RPM
-if I turn off the Jeep and re-start, it idles fine and revs past 2800 RPM
-engine lights remains on

I retrieved the following codes:
300 - Misfire detected in multiple cylinders.
302 - Misfire detected in cylinder #2.
303 - Misfire detected in cylinder #3.
462 - Fuel level sender voltage wrong.

Other info:
For about 3 years, my fuel gauge hasn’t worked.
-the gauge shows empty when tank is Full to ¼
-when tank hit ¼ to empty the gauge bounces from Full to Empty
(I had 2 dealers look at this with no success on their part…..one of the dealer replace the fuel sending unit)


I have a coolant consumption problem. I have to top it up once in a while. Absolutely no leak. Coolant smell from exhaust on cold start up.

The compression test was good.
I have check and cleaned the connector at the PCM.
I switched the coils around: same result
Replace the plugs: same result

Any ideas on what the problem(s) are?
Are they related?

Thanks in advance for the help…

 

[kj924]

Coolant doesn't just disappear...if there are no leaks visible...then it must be entering the combustion chamber via a head gasket leak....any whitish smoke from exhaust on start up...I know you said you can smell it...but do you see anything?


Sending unit issue may be a low voltage from the sending unit...seen some GM vehicles with that problem in the winter salt zone that we Canadians live in...if the sending unit was replaced with the same result as before...then wiring would be my next area to inspect....

 

[LibertyTC]

Driving with coolant entering into the chamber is asking for serious engine mishap.
How does your oil look when you pull the dipstick? Bubbles in oil? =water /Hoat particles.
How many miles on this KJ?

 

[TigerClaws]

Definitively a gasket leaking, not much other way to get coolant smell from exhaust... Anything can alter the performance of your oil in the engine, EVEN old unflushed oil will deter the new one, at some point ... Coolant isnt known to be anti-friction Bad news is: You need to change that gasket NOW, because it wont last long i can tell you !! Cylinder misfiring is probably due to not enough lubrification and pistons are frictionning instead of pumping, youll scrape the heck out of the piston's rings and sleeves ... Dont run with it and get it to the garage !!

P.S. When your engine is cold, no matter what car or make it is, NEVER rev up your engine BEFORE it is up to its regular temperature.... thats will burst the gaskets, i had a Pontiac 3.4L Grand AM, i know about gaskets ... Been there,done that ...

 

[TigerClaws]

Thing im thinking is the fact that cold start materials are skinny, with heat materials expands, your leak might be very very small. At cold start you get troubles, but once you drive it up to the stealership, the engine has heated up and gaskets expanded up to the point where there is nothing apparent... thus explaining the correct compression... Does it run good once its heated up ? Anyway, dont mess with this because this will cost you a lot more money if you dont get it fixed right away. Yes, to the point of getting a new engine... if i were you i might consider looking for a used engine at the scrap yard and see how much they will go for and how much for its installation at your favorite garage BEFORE you get the stealership to ask you if they must fix it .... You know they will steal your wallet and ask you to pay to have it back ...

I might be exagerating a bit but dont get all scared up and stuff. Just consider what i told you and make sure you check the options you have ... I have no idea how much it costs to rebuild an engine but i doubt itll be less then getting a used one ...
If your pistons/rings/sleeves are ok then all youll need is to get a new gaskets job done. Gaskets are cheap but the labor to do it is another matter... Im guessing a 3-4 hours labor job and a 30$ gasket maybe ...

 

[TopShapeCabby]

Coolant doesn't just disappear...if there are no leaks visible...then it must be entering the combustion chamber via a head gasket leak....any whitish smoke from exhaust on start up...I know you said you can smell it...but do you see anything?


Sending unit issue may be a low voltage from the sending unit...seen some GM vehicles with that problem in the winter salt zone that we Canadians live in...if the sending unit was replaced with the same result as before...then wiring would be my next area to inspect....

yes, it is a little smokey at start up, not major and not every time

I'll check the wiring again...

Driving with coolant entering into the chamber is asking for serious engine mishap.
How does your oil look when you pull the dipstick? Bubbles in oil? =water /Hoat particles.
How many miles on this KJ?

almost 200 000KM

oil is black, no bubbles or milky color

Thing im thinking is the fact that cold start materials are skinny, with heat materials expands, your leak might be very very small. At cold start you get troubles, but once you drive it up to the stealership, the engine has heated up and gaskets expanded up to the point where there is nothing apparent... thus explaining the correct compression... Does it run good once its heated up ?

that's a very good idea...I'll do a compression test with the engine cold and inspect the spark plugs again

 

[TigerClaws]

You then have might both problems maybe, sending unit, i cant help you out on this one as i dont know anything about it, but it sure wont make your KJ lose coolant ... But at almost 200 000KM, car's life shortens and we all have to expect more then 1 bugs to come out.

How ''black'' is the oil ? How many kms with that oil so far ? Oil is black ... you ran with cylinder misfiring ... I'm guessing your about 1/2 way into the usual 5000-7000kms oil change ? You'd have about 3500 km done since last oil change or maybe less ... If that's the case, expect your piston's rings and sleeves to be grinded a bit ...
My Yamaha 250 WR-F needs oil changes every 8 hours of ride done. 8 hours and the oil is pitch black, but thats the normal wear and tear for the engine. Metallic sparkles found in oil every oil change, thats what happens to engines liquid cooled and perform more then a 250cc should ... Last year i had to rebuilt the engine, first time since i had it, as it was getting less and less compression. One would usually do 2-3 years of regular riding before it all wears up and need to be rebuilt to keep performances up ...

200 000kms, i know lots of people will say you can do better with that KJ's engine and stuff, but that still has to start showing wear and tear ... If you intend on keeping the KJ, then, you know its coming so you can prepare for it and be happy to give your KJ a new life instead of being sad and depressed about the fact it let you down as you didnt expected it ...

 

[Ry' N Jen]

I need you input on issues the Liberty is having......

In the past, this would happen every 6 months but it happened everyday this week, at least once a day:
-start the Jeep, run rough (1 to 2 cylinders out)
-engine light blinks
-low power (obviously)
-as I drive, the engine cuts out every time I hit approx. 2800 RPM
-if I turn off the Jeep and re-start, it idles fine and revs past 2800 RPM
-engine lights remains on

I retrieved the following codes:
300 - Misfire detected in multiple cylinders.
302 - Misfire detected in cylinder #2.
303 - Misfire detected in cylinder #3.
462 - Fuel level sender voltage wrong.

Other info:
For about 3 years, my fuel gauge hasn’t worked.
-the gauge shows empty when tank is Full to ¼
-when tank hit ¼ to empty the gauge bounces from Full to Empty
(I had 2 dealers look at this with no success on their part…..one of the dealer replace the fuel sending unit)


I have a coolant consumption problem. I have to top it up once in a while. Absolutely no leak. Coolant smell from exhaust on cold start up.

The compression test was good.
I have check and cleaned the connector at the PCM.
I switched the coils around: same result
Replace the plugs: same result

Any ideas on what the problem(s) are?
Are they related?

Thanks in advance for the help…

I read your message but didn't read the rest here...

New plugs is all you need!

This is the second time this Exact same thing has happened to Jen and I!

First time I took it to a stealership and payed them a princely sum of
cash for them to tell me all I needed was a set of brand new spark
plugs...

This time around, I have a neat little aftermarket on board computer/code reader that posted trouble codes... And, well, after a little "Self Diagnosis".
I swapped out the plugs and all is well!
Ya, I also took a multi meter to the coil packs to see what they were putting out and all is well!

Like Geico say's... "Save 15% or more"

Check them first!

 

[Sirthor1881]

RYAN09- what type of plugs did you use that second go around? I installed some autolite platinums, and I ended up having the same issue again. I am not trying to threadjack, I am having some of the same issues. I have the same codes coming up the only difference is mine is a misfire on cyl 1and cyl 6, but I still have the multiple misfire code also.

 

[TopShapeCabby]

I read your message but didn't read the rest here...

New plugs is all you need!

This is the second time this Exact same thing has happened to Jen and I!

First time I took it to a stealership and payed them a princely sum of
cash for them to tell me all I needed was a set of brand new spark
plugs...

This time around, I have a neat little aftermarket on board computer/code reader that posted trouble codes... And, well, after a little "Self Diagnosis".
I swapped out the plugs and all is well!
Ya, I also took a multi meter to the coil packs to see what they were putting out and all is well!

Like Geico say's... "Save 15% or more"

Check them first!

I'll replace my plug to see if it resolves the misfire problem...

I'll check the conlor/condition of each plug to see if there is a difference from cylinder to cylinder.

Oh ya, I'll do a compression test while I'm there. I think I'll do the compression test with a cold engine.

 

[TopShapeCabby]

UPDATE.

-cleaned my K&N air filter
-replace the spark plugs (NGK Platinum, they didn't have regular NGK)
-cleared codes

Better startups, idles smooth, better acceleration

-I perfromed a compression test (with the engine warm): 195 on 3 cylinders and 200 on the other 3

The color of the sprak plugs is very similar.

I don't think there is a problem with the heads/head gaskets.

The other option would be a coolant leak in the intake/plenum? I will get a coolant pressure tester.

 

[journeyjim]

Some one on the site has said that the radiator will develop leaks around the top hose connection, I don't know if there is a dye for detection radiator leaks or not, thought I would throw this out to you.

 

[kb0nly]

Also check your hoses and clamps for signs of coolant leaking, should be a bit of whitish residue where the coolant leaked out and dried up.

On my KJ i was getting some unexplained coolant loss and smell of coolant, it was random. The problem was the place i bought it from put in a new radiator and hoses but only tightened them up once, never rechecked the hose clamps after a couple heating and cooling cycles. So one morning when the engine was cold i grabbed a screwdriver and sure enough the clamps were loose enough i could easily get a couple turns out of them without feeling like i was overtightening them, just snugging them up. Then i went for a drive and got everything up to normal temp and stopped again to shut off and check them, got another turn out of them before they felt tight.

After that it took a few drives to burn off any coolant still hanging around the engine bay, and after running through the carwash to clean the rest off i never smelled it again and the level no longer moves around much, just normal expansion and contraction with heating and cooling.

A few suggestions... Make sure your not overfilling, with the engine cold the coolant in the reservoir should be at the middle where the seam in the tank is. If you haven't replaced the hoses and clamps in a while do that, the factory spring loaded hose clamps weaken in time also, replace with some good quality stainless steel hose clamps, tighten down and do like i did, take it for a drive and get everything up to temp and then check tightness again. Look for leaks around hose ends. And definitely check for leaks and cracks, as it was already mentioned around the top radiator hose on the radiator is a common place for it to crack. Check the overflow hose too, both ends and make sure there is no sign of leaks and everything is tight. Also check heater hoses as well.

With the compression results you got i doubt you have a bad head gasket. I bet your just smelling a dripping coolant leak somewhere. Coolant leaks are a pain, even a small drop of it on the exhaust manifold makes enough smell to drive you nuts. And with the fan blowing and the airflow underhood it only takes a small leak like that for coolant to get blown onto the exhaust.

 

[TopShapeCabby]

I replaced the upper & lower rad hose with 4 new clamps about a year and a half ago. I did check last night if there was a leak/seep on them. They all look good.

My next step is a coolant pressure test and inspect all coolant hoses. If everything looks good, I might take the intake/plenum off to inspect and replace all the gasket. From what I understand, the coolant does go through the intake/plenum since the coolant temp sensor is located in the intake.

Thanks everyone for the input. Any more ideas?