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Topic Review (Newest First)
07-22-2013 11:28 PM
Jeepfixer1 I have run into aftermarket crank sensors giving misfiring issues. If you have your original and not sure anything was wrong with it then reinstall it and test. Remember that the crank sensor is supposed to have a small air gap between it and the flywheel. Too close and you can mess the tip of it up and too far and you will have a reading issue. It should be about the thickness of a matchbook lid (.015) or so away from the flywheel if I remember correct. Some of the ckps come with a small felt piece glued to the tip. If you put one in that has this the go ahead and let it hit the flywheel. This felt/paper sets the gap and gets knocked off when you start it. After that I would check the plugs but if you have done them twice and your last was autolites (I prefer NGK or champion in chryslers) they probably are ok.
You do have what can be a difficult problem to diagnose. Remember just because you replaced something, it's not guaranteed to be good (especially true with aftermarket parts). Now before everyone rants about how good their aftermarket parts are, I use quality aftermarket stuff everyday and most of the time it's ok! I have run into a few vehicles that have fought me on this issue though. Secondly sometimes a (GOOD) technician can save you money in the long run, especially if you are throwing parts at it . Good luck and hope this helps!
07-22-2013 09:54 PM
4wheelin
Quote:
Originally Posted by Jerry Bransford View Post
You're confusing the double-tipped term used with single gap platinum plugs with different technology plugs that have multiple electrodes/multiple gaps like the Bosch Plus2 or Plus 4.

The commonly recommended Autolite APP985 and Champion 7034 platinum coated plugs are both what is known in the industry as "double tipped"... which simply means that both sides of the gap are tipped/coated with platinum. One gap, both sides coated with platinum = double tipped. One gap, just the center electrode coated = single-tipped.

Non-platinum plugs, like the Jeep factory cheaped out with and installed into our TJs, work fine but only work fine for around 1/3 the life you'd get with a platinum tipped plug or approximately 1/6th the life of an iridium tipped plug. And non-platinum doesn't necessarily mean OEM... two of my three vehicles came with double-tipped (single electrode) platinum plugs right from the factory.

You can see in the below packaging that there is only one electrode on the spark plug that is considered a doublet-tipped platinum plug.
Right again! I misunderstood the double tipped after reading about the E3's. Mind just went in that direction when I read double tipped :-)

I wonder if the OP ever got it figured out?
07-22-2013 07:41 PM
Jerry Bransford
Quote:
Originally Posted by 4wheelin View Post
None of the suggested plugs here are double tipped. Use OEM type plugs, and you'll be fine.
You're confusing the double-tipped term used with single gap platinum plugs with different technology plugs that have multiple electrodes/multiple gaps like the Bosch Plus2 or Plus 4.

The commonly recommended Autolite APP985 and Champion 7034 platinum coated plugs are both what is known in the industry as "double tipped"... which simply means that both sides of the gap are tipped/coated with platinum. One gap, both sides coated with platinum = double tipped. One gap, just the center electrode coated = single-tipped.

Non-platinum plugs, like the Jeep factory cheaped out with and installed into our TJs, work fine but only work fine for around 1/3 the life you'd get with a platinum tipped plug or approximately 1/6th the life of an iridium tipped plug. And non-platinum doesn't necessarily mean OEM... two of my three vehicles came with double-tipped (single electrode) platinum plugs right from the factory.

You can see in the below packaging that there is only one electrode on the spark plug that is considered a doublet-tipped platinum plug.
07-22-2013 07:23 PM
jdjolly2
Quote:
Originally Posted by Jerry Bransford View Post
Since I have never run Champion plugs in any of the five Jeeps I have owned since 1989 & never had any idle problems or misfires from the plugs, I can't agree with that. Not to mention that the factory installed NGK plugs in many model years. For example, 2000 and newer TJ distributorless 4.0L engines are very fussy about the spark plugs they like to run on but certainly don't require Champions to run well. My 2004 runs fine without idle or misfires on Autolite plugs & I would expect the same with other brands like NGK, Champion, etc..

What type of plug can cause idle & misfire problems in 2000 and newer distributorless 4.0L engines? Single tipped platinums... like the Champion 3034 or Autolite AP985. 2000 and newer 4.0L engines require either conventional plugs, iridium tipped, or double-tipped platinum coated which means platinum on both sides of the gap.

And tbe misfire issue for which a TSB was issued for 2000 and newer 4.0L engines has nothing to do with the brand-name spark plug used. It has to do with the DIS ignition system requiring both sides of the gap have the same type of coating since the later 4.0L's DIS ignition system fires the plug alternately from both sides of the gap twice as often as it did when the 4.0L engine had a distributor. Again, that issue has nothing to do with spark plug brand name and everything to do with the type of coating the electrodes have.
In ten years in a chrysler dealership I have never came across a set of auto lite plugs that have run right in a chrysler engine. Is this his problem I don't know I was simply stating what has been my experience. Ngk work extremely well and are factory installed in some chrysler engines.
06-08-2013 02:52 PM
4wheelin
Quote:
Originally Posted by LSixer View Post
Interesting. I have a similar issue with my 4.0 2004. Regular subtle misfires. But, no codes. I have already decided to replace the plugs this weekend and was actually reading through posts to see what folks thought was best.
Question though, with a "double" tip plug, how do you gap it? I have gapped plenty of plugs in the past, never encountered a double tipped plug. Thanks!
None of the suggested plugs here are double tipped. Use OEM type plugs, and you'll be fine.
06-07-2013 04:38 PM
LSixer Interesting. I have a similar issue with my 4.0 2004. Regular subtle misfires. But, no codes. I have already decided to replace the plugs this weekend and was actually reading through posts to see what folks thought was best.
Question though, with a "double" tip plug, how do you gap it? I have gapped plenty of plugs in the past, never encountered a double tipped plug. Thanks!
06-03-2013 08:46 PM
Jerry Bransford
Quote:
Originally Posted by 4wheelin View Post
Wow! I never heard that the DIS ignition fires the plug alternately from both sides of the gap. Where can I read up on this?
Not all DIS ignitions fire alternately from both sides of the gap, just those where each pair of spark plugs shares a common ignition coil between them. The 4.0L is like that, there are three ignition coils for six spark plugs. So the 4.0L's plugs fire each stroke but with opposite spark polarity for each stroke.

My wife's previous 4.7L V8 Grand Cherokee also had a DIS ignition but it had an ignition coil for each spark plug... 8 ignition coils for 8 spark plugs. Same with her current 4.3L Lexus V8... it has a DIS but each spark plug has its own coil too. So the plugs for the 4.7 and 4.3 spark plugs are only fired during the compression stroke with the same polarity/the same direction across the spark plug gap, not every stroke in alternating directions like the 2000 and newer DIS version of the 4.0L engine does.
06-03-2013 08:38 PM
4wheelin
Quote:
Originally Posted by Jerry Bransford View Post
Since I have never run Champion plugs in any of the five Jeeps I have owned since 1989 & never had any idle problems or misfires from the plugs, I can't agree with that. Not to mention that the factory installed NGK plugs in many model years. For example, 2000 and newer TJ distributorless 4.0L engines are very fussy about the spark plugs they like to run on but certainly don't require Champions to run well. My 2004 runs fine without idle or misfires on Autolite plugs & I would expect the same with other brands like NGK, Champion, etc..

What type of plug can cause idle & misfire problems in 2000 and newer distributorless 4.0L engines? Single tipped platinums... like the Champion 3034 or Autolite AP985. 2000 and newer 4.0L engines require either conventional plugs, iridium tipped, or double-tipped platinum coated which means platinum on both sides of the gap.

And tbe misfire issue for which a TSB was issued for 2000 and newer 4.0L engines has nothing to do with the brand-name spark plug used. It has to do with the DIS ignition system requiring both sides of the gap have the same type of coating since the later 4.0L's DIS ignition system fires the plug alternately from both sides of the gap twice as often as it did when the 4.0L engine had a distributor. Again, that issue has nothing to do with spark plug brand name and everything to do with the type of coating the electrodes have.
Wow! I never heard that the DIS ignition fires the plug alternately from both sides of the gap. Where can I read up on this?
06-03-2013 02:01 PM
Jerry Bransford
Quote:
Originally Posted by jdjolly2 View Post
I've been a tech in a chrysler garage for ten years its been my experience that anything but champion plugs can cause misfires and poor idle..
Since I have never run Champion plugs in any of the five Jeeps I have owned since 1989 & never had any idle problems or misfires from the plugs, I can't agree with that. Not to mention that the factory installed NGK plugs in many model years. For example, 2000 and newer TJ distributorless 4.0L engines are very fussy about the spark plugs they like to run on but certainly don't require Champions to run well. My 2004 runs fine without idle or misfires on Autolite plugs & I would expect the same with other brands like NGK, Champion, etc..

What type of plug can cause idle & misfire problems in 2000 and newer distributorless 4.0L engines? Single tipped platinums... like the Champion 3034 or Autolite AP985. 2000 and newer 4.0L engines require either conventional plugs, iridium tipped, or double-tipped platinum coated which means platinum on both sides of the gap.

And tbe misfire issue for which a TSB was issued for 2000 and newer 4.0L engines has nothing to do with the brand-name spark plug used. It has to do with the DIS ignition system requiring both sides of the gap have the same type of coating since the later 4.0L's DIS ignition system fires the plug alternately from both sides of the gap twice as often as it did when the 4.0L engine had a distributor. Again, that issue has nothing to do with spark plug brand name and everything to do with the type of coating the electrodes have.
06-03-2013 01:55 PM
bigeyed76 I am having the same issues..I replaced both the O2 sensors and I have replaced the CPS and it went away for a while then back again and this time even worse miss fire.. I am at a loss too.. I have a cracked boot on top of the head cover but that cant be it can it? I got stranded the other day when I shut the engine off it would not start until it cooled down..Now it will start but not run down the road...?
05-18-2013 09:07 PM
JREDmoto11 Have you figured it out yet bagged92sdime? I'm still having issues... Extremely frustrating
05-16-2013 07:21 PM
jdjolly2 I've been a tech in a chrysler garage for ten years its been my experience that anything but champion plugs can cause misfires and poor idle. Also don't over look o2 sensors they can cause misfires and be intermittent. Yours is tough also never tape a rubber boot replace it because vacuum leaks will cause it to run bad as well.
05-16-2013 07:10 PM
JREDmoto11 I'm having similar problems with my TJ, and have been dealing with them for sometime. Any updates would be appreciated, since I've tried all that I can think of. I'm throwing at the moment are p0300,p0335,p0339. Codes that I have recently thrown are p0457, p0421,p0431,p0222... Have done plugs,coil,oil,filter,air filter, basic maintenance as well as CKP sensor (a lot of dirt was in it), battery terminals, cleaned TPS. I'm thinking a bad connection? Or short in the harness? This all started with what I had thought was the Cat going bad, so I did basic maintenance listed above as well as gut the pre cats, since the front one had melted and a ball of titanium was resting in the down pipe causing a clog. Inspected rear cat as well(all good) reset the ECM and she was golden for awhile... Now I'm battling this, any ideas?
04-25-2013 08:46 PM
4wheelin
Quote:
Originally Posted by bagged92sdime View Post
Holding off on the TPS...I ran it up to about 4-4500rpms and no CEL...WTF...Talked to a local shop today and they said maybe the fuel pressure regulator...
Man, you really got a tough one. I recall reading some folks get a bad TPS or Crank Position sensor right off the shelf. Do you have a jeep group near you that can help you out by testing some parts between vehicles?

I would think fuel pressure would always be off and not intermittent.

I know you replaced plugs, but those can break too. Take them out and verify they are still intact. Don't just look at them, move and pull on the ceramic and electrode. Check the gap while you're at it. Ignition problems can be a pain to troubleshoot. Keep at it. You'll figure it out.
04-24-2013 11:03 PM
bagged92sdime Holding off on the TPS...I ran it up to about 4-4500rpms and no CEL...WTF...Talked to a local shop today and they said maybe the fuel pressure regulator...
04-24-2013 04:46 PM
bagged92sdime So the problem randomly went away yesterday...No codes, no more CEL...WTF? Did everything I could to see if it would come back...Still nothing...Cool!

Went to pass some lady today and mashed on it...Got around her, slowed down and turned...CEL came back...Got home and sat in the driveway in park, ran it up to 2k and the CEL came back. I disconnected the battery for about 10 mins. No CEL...until about 3k driving down the road.

Pulled in the parking lot at work...Locked it in first gear and ran it up to 3500 (about 20-25mph), nothing....WTF!?!?!?!

Rocky Bar, I'm gonna go get a TPS today and give that a try...Thanks!
04-19-2013 12:50 PM
Rocky Bar
Mis-fire

Here's another idea. When I was chasing my miss, the TPS sensor on throttle body was going to be the next item to replace when I found the miss. (bad plug). Keep us posted. I know you'll find it.
04-19-2013 12:22 PM
bagged92sdime Anybody have any other ideas? I would prefer figure it out rather than take it to a shop...
04-17-2013 08:44 PM
bagged92sdime Well, I checked the intake manifold...I tightened down some bolts a little more, tightened up the throttle body a bit and wrapped the end of a breather line from the valve cover to the intake manifold with electrical tape (had a crack in the boot)...Still no luck...Could the CKP not be in far enough or too far? Is that even possible? Just seems a little odd that right after replacing the CKP that it starts doing this. I mean, it stopped when I put copper core Autolites in, but it's back again...

I'm really at a loss here...Aside from replacing the intake manifold gasket, rebuilding the injectors and replacing all the vacuum lines, I have no clue...
04-17-2013 02:20 PM
Rocky Bar
Mis- fire

Had an slight engine miss like you a while back. (97 TJ 4.0)(95k on OD) All electrical parts only had about 10k since changing them out. Bought new cap/rotor/wires, not plugs. Still had miss. Added fuel booster as it might have been bad gas. Still had miss. Was told that it could be air leak on sensor on intake manifold, as they go bad. That was all good. Decided to go after the plugs, but they only had 10k on them. Well found that #6 plug was cracked at tip at electrode. Installed new Champions, and all is good. You might check your intake system for air leaks. Keep us posted.
04-17-2013 01:23 PM
bagged92sdime Decided just for sh!ts and giggle to replace the gas cap...Didn't help...
04-17-2013 04:52 AM
bagged92sdime Yeah, the PO300 is random misfire detected...Somebody else said something about the gas cap...Hmmm...I may look into that...
04-15-2013 04:09 PM
4wheelin
Quote:
Originally Posted by bagged92sdime View Post
So went and got gas today...Yeah, flashing CEL is back...Code PO300..Random Misfire Detected...

WTF! I'm really starting to hate my Jeep...

New coil pack, new plugs, new crank sensor, new cam sensor, new temp sensor, new brushes in the alt...Yeah, this sucks...
Well, I'm going to take a stab at this and suggest your gas cap. That sounds like the common denominator here, since you say you just got gas. I haven't looked up that Code, assuming you have already done that.

Hope this helps,
04-15-2013 03:49 PM
bagged92sdime BTW, speed sensor on mine is a newer (about a year old) teraflex tone ring style for the Terflex extreme short sye...
04-15-2013 03:47 PM
bagged92sdime So went and got gas today...Yeah, flashing CEL is back...Code PO300..Random Misfire Detected...

WTF! I'm really starting to hate my Jeep...

New coil pack, new plugs, new crank sensor, new cam sensor, new temp sensor, new brushes in the alt...Yeah, this sucks...
04-08-2013 11:45 PM
Raif I had very similar misfire problems... would start to misfire after hitting a bump, and would buck like a horse above 3k RPM. Turned out it was a bad VSS (spedo sensor) and a dirty CPS. Glad you got it all sorted!
04-08-2013 04:40 PM
Jerry Bransford First on my list of plugs not to run would be E3s. Second would be Bosch Plus-2 or Plus-4. Three superb plugs for 2000 and newer 4.0L engines include the Autolite XP985 iridium (good for 200k miles) or the dual tip platinum Champion 7034 or Autolite APP985 which are both good for 100k miles. 2000 and newer 4.0L engines are picky about their plugs. In addition to the above plugs, you can run nearly any conventional resistor-type copper core plug but they will only be good for 25-35k miles.

For '99 and older 4.0L and all 2.5L engines, I'd go for the single-tipped platinum Autolite AP985, Champion 3034, or the iridium Autolite XP985. Or a conventional resistor-type plug which will run fine but give less life as described above.
04-07-2013 11:40 PM
bagged92sdime Hope yours gets figured out...

I ended up throwing some Autolite copper plugs in ($1.99 at Napa)...Problem solved (running smooth, no codes, no nothing)...Guess all that stuff about the E3's not working very well with a coil pack ignition is true...
04-06-2013 06:24 PM
4wheelin Most posts on here say the E3's are NOT a good idea. While I suggest OEM style plugs, I'm not gong to say that's the solution to your problems. But, it is a good and inexpensive start.
04-06-2013 06:13 PM
bagged92sdime BTW, I should say with the overheating problems I mentioned, I had a cheap-o electric fan on it that didn't seem to keep up with cooling it off out on the trail - fine for around town, but not much else, so I swapped back to an OE fan and decided might not be a bad idea to replace the temp sensor...Oh and it has a new thermostat as of OCT '12...My old thermostat broke and was in pieces inside the thermostat housing...
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