Jeep Wrangler Forum

Jeep Wrangler Forum (http://www.wranglerforum.com/)
-   TJ Tech Forum (http://www.wranglerforum.com/f210/)
-   -   The dreaded misfire (http://www.wranglerforum.com/f210/the-dreaded-misfire-230572.html)

Deathmask 03-26-2013 07:07 PM

The dreaded misfire
 
So I got my TJ with a misfire (p0300 p0301 p0302 and sometimes p0201 and p0202) thinking all I had to do to fix it was a tune up.... That wasn't the case. I've been doing a lot of reading about people replacing the valve springs and it not getting rid of the misfire. I was also reading about the Bosche injectors being awesome. Theoretically could replacing all 6 injectors and swapping in some of the quad tip or whatever they are called spark plugs smooth it out and get rid of the misfire?

jp2611 03-26-2013 07:13 PM

IMO nope......TJ's old fashioned Jeep likes old fashioned plugs....yeah there is a thread fro that somewhere......and there is another thread that tells you what the codes are for...first guess from experience would be 02 sensors, second would be the Cat...don't see the year of your Jeep but assuming it doesn't have the coil rail, that leaves plugs and wires......I would check the codes and do the tuneup since it seems you don't know when it was last done....GL!!

Deathmask 03-26-2013 07:26 PM

It's an 2002 so it does have a coil rail which I have already replaced along with replacing the plugs with "old fashion" plugs. I've already checked the codes 300- random misfire 301. misfire cylinder 1 302. misfire cylinder 2 201. Open in injector 1 202. Open in injector 2.

RypH 03-26-2013 07:57 PM

My '97 was plagued with a misfire (36k miles) but would run dandy while in cold loop startup. Someone on a forum long ago swore it was the infamous TSB'd valve springs and I needed them replaced. I bawked at it. The misfire cleared up with a fresh set of plugs but within 6k miles went right back to misfiring at warmup. Long story short.....it was faulty plug wires. I now have 150k and valve springs are still doing quite well.

Deathmask 03-26-2013 08:06 PM

I'm with you, I rather not do the valve springs. I wish I could clear mine up that easily.... After replacing the coil rail and plugs and cleared the codes the CEL stayed off for a couple days but once the computer went through all it's check around 50 miles it started again and the light was back.

jp2611 03-26-2013 08:18 PM

Quote:

Originally Posted by Deathmask (Post 3556173)
It's an 2002 so it does have a coil rail which I have already replaced along with replacing the plugs with "old fashion" plugs. I've already checked the codes 300- random misfire 301. misfire cylinder 1 302. misfire cylinder 2 201. Open in injector 1 202. Open in injector 2.

So here is my question/ or maybe thoughts..... and understand my "logic" could well be wrong.

Misfire codes on a TJ with a coil rail, (especially a new coil rail) have to do with the timing, which is controlled by the computer which gets its info from the sensors, and in turn adjust based on info to the sensors, so if there is a bad sensor...it gives garbage info to computer...which in turn adjusts based on the info from the sensor....(garbage in = garbage out) but another sensor would catch the misfire...so based on what I have seen on this Forum, and not having any clear problem/ knowing what is wrong....02sensors do wear out and mileage goes down and sometimes throws codes and sometimes doesn't......these are not the only sensors that can do this but are the first ones that come to mind.....I chased a CEL for a couple years...never came on till the jeep sat and idled for a few minutes...not even at stop lights..and if I revved the motor never came on at all.......finally swapped 02sensor...problem solved

Deathmask 03-26-2013 08:41 PM

Since I'm getting a misfire in cylinder 1 and 2, would I be safe in assuming it would be the front upstream or downstream o2 sensor? If it is the o2 that is.

jp2611 03-26-2013 08:45 PM

Quote:

Originally Posted by Deathmask (Post 3556497)
Since I'm getting a misfire in cylinder 1 and 2, would I be safe in assuming it would be the front upstream or downstream o2 sensor? If it is the o2 that is.

Anything I say is a "guess" because I can not remember which is which, the theory I used is to replace both...if one is bad good chance the other is bad or close to going bad also....slight caution....I got lucky...I didn't buy OEM I bought the "cheap ones" but I have had no issues...if I had it to do over I would have got the OEMs....NTK or NGK..not sure which

Deathmask 03-27-2013 07:04 PM

Is there a typical location (before or after the cat) that goes out more ofter? Because I'm only getting a misfire code from cylinders 1 and 2 I'm thinking I would only need to replace the sensor for the front cylinders. I will eventually replace the others but at the moment I would like to save money where I can to replace my Dana 35 before my 35's blow it up.....

On my home from work my CEL started flashing at me (danger to cat). Would a o2 sensor still be the likely culprit or is it still a guessing game?

viperx6x9x 03-27-2013 11:00 PM

I think O2's are a seperate problem. I am getting an engine light and the code is P0161. Which is O2 sensor 2 (i am told sensor 2 is the downstream one). Mysteriously the light went away though.

another thought, and bear with me because this is a problem i had with my 03 silverado, I had a misfire going on with that. No check engine light accompanied it but you could literally feel the misfire at idle. So i took it to the dealer and their code reader caught the misfires. Turns out the electrical connectors on 3 of the injectors were loose. So the injectors were not spraying fuel at the right times due to not getting the signal to open.

So give those connections a look. It could be that simple.

also i don't know much about the 4.0 engine, but does it have seperate plug wires running from the coil packs to the spark plugs? If so, swap in some new plug wires too. Those things go bad over time as well.

slathrum 03-27-2013 11:29 PM

I can tell you that changing the fuel injectors on my 2001 XJ completely solved the misfiring issues. It's pretty well known that the 2000 and 2001 XJ's with 4.0's had a problem with the injectors vapor locking due to heat soak from the exhaust manifold to the intake manifold. I've noticed my new to me 2005 TJ has a little bit of insulation on the top side of the manifold, but that's about the only difference.

If I remember correctly, there is a guy that rebuilds 19lb Mustang fuel injectors that are a direct swap. The spray design is supposed to be significantly better, and for me, my XJ ran much smoother and the misfiring issues went away. It's been a while, but I think I was getting the same engine code you are. My TJ stumbles every once in a while after a longer trip where it gets good and warm for an extended time, so I'm planning on the same upgrade soon. I'll have to find the website, but I know it was less than $150 for all six injectors.

viperx6x9x 03-28-2013 12:49 AM

That could be the problem too. My 02 TJ has a rough idle sometimes but it hasn't been throwing codes other than the recent O2 code. It has been idling rough for months though so I don't know if it the O2 has anything to do with it.

Go figure though, you throw some ford parts on a chrysler and it starts working right. :)

Deathmask 03-28-2013 02:00 AM

I think I'm going to look into the known problem (injectors 1 and 2) before I throw o2 sensors at it without an o2 code being present. I would rather spend $150 on improved injectors than $150 on something that I don't for sure need yet.

viperx6x9x 03-28-2013 04:20 AM

Yeah i think you should stick with injectors and spark plugs for now. I am not too knowlegeable on how O2 sensors work, but it doesn't seem they would effect individual cylinders like your problem.

only other thing i can think of, is there a sensor on each cylinder that is telling the PCM it didn't fire when it should have? if so maybe those sensors went bad or have a bad connection.

you already replaced the coils and plugs, so that should cover the electricity delivery. unless somehow the plugs weren't gapped correctly, that could effect your spark.

best bet seems like it should be the injectors or maybe loose connection to the injectors. Maybe the injectors are clogged up, do you ever put any injector cleaner or fuel system cleaner through your jeep?

showtime 03-28-2013 06:22 AM

Have a 04 tj with similar prob.,replaced coil pac,o2 sensors and next step was going to be injectors,any one have a link to the injector upgrade.:thumb:

slathrum 03-28-2013 06:41 AM

Just Google mustang remanufactured or reconditioned 19 lb injectors. Seems odd, but that's the most cost effective way to go about it. They have the same improved 4 spray nozzles. I've found them between $100 and $200 that way, completely cleaned, rebuilt and flow tested.

Once you have the injectors, the swap is a piece of cake. You just bleed off the pressure at the fuel rail and then carefully unbolt and remove it. Definitely wait to do this until it's been sitting for a while. You don't want to press that relief valve on a freshly pressurized line. Make sure you have a rag to catch the small amount of fuel that will come out too. The old injectors may be a little gummed in there, but they will pull right out and the new ones go right in. Replace the fuel rail and connect all the wiring harness connections and you're good to go!

Deathmask 03-28-2013 08:17 AM

Quote:

Originally Posted by viperx6x9x (Post 3562504)
Yeah i think you should stick with injectors and spark plugs for now. I am not too knowlegeable on how O2 sensors work, but it doesn't seem they would effect individual cylinders like your problem.

only other thing i can think of, is there a sensor on each cylinder that is telling the PCM it didn't fire when it should have? if so maybe those sensors went bad or have a bad connection.

you already replaced the coils and plugs, so that should cover the electricity delivery. unless somehow the plugs weren't gapped correctly, that could effect your spark.

best bet seems like it should be the injectors or maybe loose connection to the injectors. Maybe the injectors are clogged up, do you ever put any injector cleaner or fuel system cleaner through your jeep?

I might think it was the forward o2 sensors if there was a misfire in cylinder 3 also, but since just one and two have a misfire code along with an injector code I'm leaning more towards injectors.

I will check the connectors, harness, coil connection and plugs this weekend.

In the three weeks I've owned it I've ran two tanks with sea foam, one tank with gumout, and sea foamed the motor twice through a vacuum line.

Quote:

Originally Posted by showtime (Post 3562590)
Have a 04 tj with similar prob.,replaced coil pac,o2 sensors and next step was going to be injectors,any one have a link to the injector upgrade.:thumb:

For new injectors you can check precision auto injectors. I have not bought from them and haven't looked into the company so I don't know how reputable they are, I just know that they have the Bosch injectors and they've done a very through YouTube demo on the Bosch injectors that impressed me and made me want the Bosch injectors.

http://www.precisionautoinjectors.co...c?categoryId=3

http://www.youtube.com/watch?v=bHf-6ohkgbA

Deathmask 03-28-2013 08:24 AM

Quote:

Originally Posted by slathrum (Post 3562620)
Just Google mustang remanufactured or reconditioned 19 lb injectors. Seems odd, but that's the most cost effective way to go about it. They have the same improved 4 spray nozzles. I've found them between $100 and $200 that way, completely cleaned, rebuilt and flow tested.

Once you have the injectors, the swap is a piece of cake. You just bleed off the pressure at the fuel rail and then carefully unbolt and remove it. Definitely wait to do this until it's been sitting for a while. You don't want to press that relief valve on a freshly pressurized line. Make sure you have a rag to catch the small amount of fuel that will come out too. The old injectors may be a little gummed in there, but they will pull right out and the new ones go right in. Replace the fuel rail and connect all the wiring harness connections and you're good to go!

Is there any particular year or would any year work?

slathrum 03-28-2013 11:15 AM

From what I understand, any year should work as long as it's a 19 lb injector. The main advantage to using those is that they have the 4 nozzles instead of one without having to buy the more expensive Bosch injectors. They must be getting harder to find though, cause I'm having a hard time finding the ones I used before. That website you listed was the place I got mine from before I think. The ones I used had an orange body.

Deathmask 03-28-2013 11:34 AM

Alright I'll have to look for a set. I've found a set or reman'd Bosch on eBay from a seller with 99.9% positive feed back, but I'm having a hard time bringing myself to buy a major component off eBay....

slathrum 03-28-2013 11:56 AM

Well, I found a guy selling them on Craigslist too...

Jerry Bransford 03-28-2013 12:24 PM

Exactly what spark plug brand & model are you running? Some types of spark plugs, especially single-tipped platinum plugs like the Champion 3034 or Autolite AP985 will cause misfires in 2000 and newer 4.0L engines after they have been installed a short while.

I really doubt it's a bad or clogged fuel injector, the OE injectors just aren't known for causing problems. And you can prove that one way or the other by moving the fuel injectors around to see if the problem follows any particular fuel injectors. Like swap your #1 and #2 fuel injectors with #5 and #6 and see if the misfires follow the fuel injectors. It only takes a few minutes to swap injectors around.

slathrum 03-28-2013 12:52 PM

I would have thought that too, but switching around fuel injectors resulted in the same cylinder DTC's in my XJ. The problem was heat getting to the stock injectors, which apparently weren't up to the job. Unfortunately, our engines are designed to run hot and the injectors sit on an intake manifold that's directly about the exhaust manifold. It's a pretty common problem in XJ's. Doesn't seem to be talked about much in TJ's, but that might be because the symptoms aren't quite as severe. My TJ just happens to run similarly to how my XJ did before I did the swap, though I'm not getting any DTC's with my TJ. To me, it's worth the upgrade at $100 or so that's been proven to me in the past.

Jerry Bransford 03-28-2013 12:55 PM

It makes no sense to swap out the fuel injectors until it has been shown the misfire will follow the injector from the misfiring cylinder(s) around. Not to mention that just throwing parts at a problem in hopes of a fix is very expensive.

And if the problem is heat-soak related, new injectors aren't the fix. There is a TSB for heat soak that basically involves placing foil-backed insulation under the injectors.

slathrum 03-28-2013 08:21 PM

Yeah, been there and done that. Spent about $50 in high temp insulation with little to no benefit. The 4 nozzle fuel injectors vaporize/atomize fuel more efficiently. Do you disagree with that? I have personally experienced a realized benefit of a smoother idle, improved acceleration and the complete resolution of my misfiring problems with this upgrade. I understand that you don't see the value in that or doubt that it is possible, but I do. Others have experienced this as well. Like I said, maybe the fixing of the misfiring was just due to having a fresh and clean injector, but there are other benefits as well. :thumb:

Deathmask 03-28-2013 08:31 PM

Quote:

Originally Posted by Jerry Bransford (Post 3563678)
Exactly what spark plug brand & model are you running? Some types of spark plugs, especially single-tipped platinum plugs like the Champion 3034 or Autolite AP985 will cause misfires in 2000 and newer 4.0L engines after they have been installed a short while.

I really doubt it's a bad or clogged fuel injector, the OE injectors just aren't known for causing problems. And you can prove that one way or the other by moving the fuel injectors around to see if the problem follows any particular fuel injectors. Like swap your #1 and #2 fuel injectors with #5 and #6 and see if the misfires follow the fuel injectors. It only takes a few minutes to swap injectors around.

I think they are NGK iridium plugs and I think the plugs I took out were autolite.

I'm not sure if it's the injector either, the wires to the injector connectors have some of the insulation peeling up a little. Maybe it's not getting the correct power it needs. I'll try to test it with my volt meter later.

Jerry Bransford 03-28-2013 08:33 PM

Quote:

Originally Posted by slathrum (Post 3565450)
Yeah, been there and done that. Spent about $50 in high temp insulation with little to no benefit. The 4 nozzle fuel injectors vaporize/atomize fuel more efficiently. Do you disagree with that? I have personally experienced a realized benefit of a smoother idle, improved acceleration and the complete resolution of my misfiring problems with this upgrade. I understand that you don't see the value in that or doubt that it is possible, but I do. Others have experienced this as well. Like I said, maybe the fixing of the misfiring was just due to having a fresh and clean injector, but there are other benefits as well. :thumb:

Once again, it is free, quick, and easy to swap the injectors around to see if the misfire follows a particular injector. If it follows an injector, the problem has been isolated to a fuel injector. If the misfire doesn't follow an injector, the problem is not with injectors.

This is just basic troubleshooting that is free and quick to do rather than spending big $$$ buying a new set of injectors that may or may not help. I guess some would rather throw parts at a problem instead of doing the simple and free basics first.

Deathmask 03-28-2013 11:01 PM

I see both of your view points. Yes I would like to not spend money if I don't have to, but after seeing that demo video of the 4 hole injectors compared to the OEM injectors I was blown away by the design differences. I also like the feed back I've heard about doing the upgrade. I am going to try to fix the problem without buying them but I would like to upgrade them eventually.

viperx6x9x 03-28-2013 11:12 PM

I agree, I don't like spending money unless the component really needs to be replaced. But if I ever have to replace an injector, I am just going to do the upgrade on all of them. For $100 that ain't a bad upgrade. Better fuel atomization can help with mpg's and at todays fuel prices that upgrade will pay for itself.

So swapping around the injectors to prove they are bad sounds like a really good idea. I try all the little things I can think of before I go buy replacement parts but I did not think of that one, thanks Jerry.

slathrum 03-29-2013 12:24 AM

That sounds like a pretty smart plan. I didn't mean to imply that troubleshooting them shouldn't be done. I did that myself, and installed heat shielding and still had the misfire with DTC's showing up on the same cylinders. Replacing the injectors was the last thing I did, and it just happened to completely resolve the issue. Good luck!


All times are GMT -5. The time now is 12:40 AM.