Jeepinaround
New member
Sweeet thanks. While I am getting the head done, anything else I should change while I have it open? Lifters? Push rods? The engine was running perfectly prior to the burnt valve.
Jeep TJ cylinder 3 misfire, please help me diagnose
- Thread starter Jeepinaround
- Start date
Sweeet thanks. While I am getting the head done, anything else I should change while I have it open? Lifters? Push rods? The engine was running perfectly prior to the burnt valve.
JPNinPA
Well-known member
Was there any knocking noise or noisy lifter? Inspect them if high milage change for piece of mind.
Also look at cam for worn lobes.
But not really necessary to change more.
Sent from my iPhone using Jeepz.com mobile app
Also look at cam for worn lobes.
But not really necessary to change more.
Sent from my iPhone using Jeepz.com mobile app
Jeepinaround
New member
So I did a leak down test, and there was no significant leakdown in any of the cylinders. I repeated the test and got the same results. Also did a wet compression test and got normal results. I don't think I will be tearing it apart just yet. There has to be something I haven't considered...
JPNinPA
Well-known member
Just to restate your issue. The rough running and misfire happens below 2000 rpm. It does not matter if started cold or warm or at idle or running while driving. It only happens below 2k rpm.
I still say that fuel pressure oscillating is not normal. It should be steady like it is at 2k rpm.
Do you mind posting the values by cylinder that you measured on both the compression and leak down test?
While you had the plugs out to do the compression test and leak down did you look at them? Mind posting pics? Tip, threads and ceramic.
And of the boot that goes over the plug?
Have you ever taken the intake or exhaust off? Or let me ask it differently. Was the intake or exhaust manifold ever off of the engine?
Also the paper or rag you hold near the exhaust does not show any sucking in. You need a flat sheet closer to the exhaust. It should always be being pushed away. A bad valve would suck the paper in the pipe. It should almost pull it out of your hand. Actually I don't hear any miss firing more like no firing. No backfiring.
Have you ever pulled the ODPA oil drive pump assembly? The thing that sits where the distributor would be. On 04-06 there was a huge issue but timing can be off on any vehicle if either the ODPA is set wrong or it's gears are worn. BE WARNED you can't just pull it out and stick it back in. There are directions to follow, so you don't miss a tooth and throw the timing way off.
How good is the ground from the battery to the engine? If measuring res it should be less than 1ohm.
What is your battery voltage off, at idle, at 2000rpm or higher?
Lastly do you have a field service manual? Find one and buy it. It has every test and measurement. Described correctly.
Regards,
JPNinPA
Sent using TapTalk
I still say that fuel pressure oscillating is not normal. It should be steady like it is at 2k rpm.
Do you mind posting the values by cylinder that you measured on both the compression and leak down test?
While you had the plugs out to do the compression test and leak down did you look at them? Mind posting pics? Tip, threads and ceramic.
And of the boot that goes over the plug?
Have you ever taken the intake or exhaust off? Or let me ask it differently. Was the intake or exhaust manifold ever off of the engine?
Also the paper or rag you hold near the exhaust does not show any sucking in. You need a flat sheet closer to the exhaust. It should always be being pushed away. A bad valve would suck the paper in the pipe. It should almost pull it out of your hand. Actually I don't hear any miss firing more like no firing. No backfiring.
Have you ever pulled the ODPA oil drive pump assembly? The thing that sits where the distributor would be. On 04-06 there was a huge issue but timing can be off on any vehicle if either the ODPA is set wrong or it's gears are worn. BE WARNED you can't just pull it out and stick it back in. There are directions to follow, so you don't miss a tooth and throw the timing way off.
How good is the ground from the battery to the engine? If measuring res it should be less than 1ohm.
What is your battery voltage off, at idle, at 2000rpm or higher?
Lastly do you have a field service manual? Find one and buy it. It has every test and measurement. Described correctly.
Regards,
JPNinPA
Sent using TapTalk
Last edited:
JPNinPA
Well-known member
Still think the jumpy fuel pressure is a cause or symptom.
So you didn't give all the info.
And there is no such a thing as analysis paralysis. Unless you make no changes. It just sounds cool and a pressuring statement.
From another forum:
"Replaced the coil and absolutely no difference. Also put on the injector 3 shield and no difference. I notice it begins right after the vehicle warms up and goes into open loop. Also, I notice that the injector 3 doesn't click as strong as the rest (by placing my finger over each injector). "
"Thank you for the reply! It's exactly as you say, when I clear the code, the jeep behaves better for a while until it throws the code again. Although I put the heat shield on and it is not making any difference. Was wondering what else I can try to make this misfire gremlin go away."
So when you clear the codes it runs fine for a while? Then it is a sensor.
And it only happens after warmup.
Try measuring the temp sending unit resistance from cold as the engine heats. It should be steady resistance change.
Regards,
JPNinPA
Sent using TapTalk
So you didn't give all the info.
And there is no such a thing as analysis paralysis. Unless you make no changes. It just sounds cool and a pressuring statement.
From another forum:
"Replaced the coil and absolutely no difference. Also put on the injector 3 shield and no difference. I notice it begins right after the vehicle warms up and goes into open loop. Also, I notice that the injector 3 doesn't click as strong as the rest (by placing my finger over each injector). "
"Thank you for the reply! It's exactly as you say, when I clear the code, the jeep behaves better for a while until it throws the code again. Although I put the heat shield on and it is not making any difference. Was wondering what else I can try to make this misfire gremlin go away."
So when you clear the codes it runs fine for a while? Then it is a sensor.
And it only happens after warmup.
Try measuring the temp sending unit resistance from cold as the engine heats. It should be steady resistance change.
Regards,
JPNinPA
Sent using TapTalk
Last edited:
Jeepinaround
New member
Thank you for the reply. Haven't gotten around to working on it due to work. Hopefully will have a chance in a few days.
Where it currently sits, its throwing a cylinder 1 code now. I was ale to start and drive it for about 10 minutes without a single hiccup or hesitation. I turned it off and restarted and it began doing it again. I have the following parts waiting for me
iridium spark plugs
Fuel pump relay
Map sensor
All 4 NTK oxygen sensors.
Have never taken the intake or exhaust off. The compression values were all about 160+/- 10psi. Leak down test I used the compression testor and hooked it up to an air tank, brought the piston to top dead center and tested each cylinder. Did not leak any air over the 15 minutes I allowed for each cylinder.
If I replace the above parts and it still does the issue, next thing I will replace is the fuel pump, followed by the coolant temperature sensor.
At that point, there is nothing left for me to change and I will have to take it into a local shop to help me out. Ideally, they could identify the issue and I can swap it out at home. Found a local head shop which has entire heads ready for a fair price, but the negative dry and wet compression tests as well as the leak down test makes me not suspect the problem being internal (and also, it has bouts of running just fine, so if it was mechanical, this would not be possible)
JPNinPA
Well-known member
Send a pic of the old plugs by cylinder showing tip thread and ceramic.
Check the wiring to all sensors as you change them.
To clarify and please correct. Details are great value.
If you reset the codes by disconnecting the battery and shorting the pos cable to negative for 30 sec. Then reconnecting the battery.
The issue does not happen until up to temperature and some driving?
How far or how many starts until it repeats. Or as soon as it heats it's back?
And once the code is thrown it happens each start as soon as it reaches temp.
Regards,
JPNinPA
Sent using TapTalk
Check the wiring to all sensors as you change them.
To clarify and please correct. Details are great value.
If you reset the codes by disconnecting the battery and shorting the pos cable to negative for 30 sec. Then reconnecting the battery.
The issue does not happen until up to temperature and some driving?
How far or how many starts until it repeats. Or as soon as it heats it's back?
And once the code is thrown it happens each start as soon as it reaches temp.
Regards,
JPNinPA
Sent using TapTalk
Last edited:
Jeepinaround
New member
I will do as you mentioned and get back to you. Made another video update of where I am:
I fix a vacuum leak from the CCV as well as show my leak down test apparatus. Repeated in all 6 cylinders x2 over (took forever).
JPNinPA
Well-known member
Brake cleaner is fairly harsh.
Water, WD 40, TB cleaner, carb cleaner all work as well and less harsh.
CRC brakekleen has toluene in it and that reacts with many materials. It is used as paint thinner and can melt/degrade rubber.
“Toluene is a common solvent, e.g. for paints, paint thinners, silicone sealants,[20] many chemical reactants, rubber, printing ink, adhesives (glues), lacquers, leather tanners, and disinfectants.[19]”
Sent from my iPhone using Jeepz.com mobile app
Water, WD 40, TB cleaner, carb cleaner all work as well and less harsh.
CRC brakekleen has toluene in it and that reacts with many materials. It is used as paint thinner and can melt/degrade rubber.
“Toluene is a common solvent, e.g. for paints, paint thinners, silicone sealants,[20] many chemical reactants, rubber, printing ink, adhesives (glues), lacquers, leather tanners, and disinfectants.[19]”
Sent from my iPhone using Jeepz.com mobile app
Last edited:
Gennybro
Active member
I used WD 40 on a new sterret dial caliper thinking I was taking well taken care of it. It desolved the glue that holds the measureing plate on to the caliper. So be careful, in my opinion. Anything that acts as a penetrite , you have to think about it.
Jeepinaround
New member
Finally figured out the issue. A hard lesson learned - here is the final video. Glad she is running smoothly now. How this helps others in the future!
JPNinPA
Well-known member
No sound for some reason.
Glad you got it fixed.
FYI they were autolite APP985 plugs in the video. You mentioned Bosch
You mentioned 10-15k miles on those plugs but you said they are pretty new in a video.
First post
“... Checked all spark plugs, all gap within range installed 2 years ago...”
Post #25
“... Plugs are champion 7034 and gap was about .035 on all 6. No fouling or gas smell on any of them. ...”
Just noting you have been all over with data. Or not up front with info.
Just use this as a learning opportunity. I did.
Sent from my iPhone using Jeepz.com mobile app
Glad you got it fixed.
FYI they were autolite APP985 plugs in the video. You mentioned Bosch
You mentioned 10-15k miles on those plugs but you said they are pretty new in a video.
First post
“... Checked all spark plugs, all gap within range installed 2 years ago...”
Post #25
“... Plugs are champion 7034 and gap was about .035 on all 6. No fouling or gas smell on any of them. ...”
Just noting you have been all over with data. Or not up front with info.
Just use this as a learning opportunity. I did.
Sent from my iPhone using Jeepz.com mobile app
Last edited:
Similar threads
