I have a 2000 xj and replaced the engine in January then months ago it started to do this stutter as if it were gasping for breath. Then the check engine light came on and the stutter slowly got worse to the point where I had misfires and it would die. It won't do this unless I'm going about 50 mph.

I read the codes and it said misfire o2 censor fail and failure in ignition coil a b and c. I just replaced the coils last night with brand new pack and on the drive home it still stuttered terribly at 50 mph and check engine light back on. Hasn't died yet and haven't had a loss in power like a misfire yet.

Once it starts to stutter it'll keep going like that until it either dies or I shut it off. If I turn it right back on after either of those happening it sounds like the brand new engine I put in it.

The kicker is this isn't constant. It doesn't happen every time I hit that speed so getting a vid up is hard to do.

Anyone have any ideas because the reader isn't saying anything new


Thanks for any and all help

Nick

 

Sounds like heat soak to me.

http://www.naxja.org/forum/showthread.php?t=1022177

 

But wouldn't it misfire and have all these problems in idle too? I only get it when I get up to about 50 mph

 

And it does it when cold too before it has time to heat up

 

I had a similar misfire in my Jeep XJ--with 220000 miles--after much searching it turned out that I had slow opening--stuck exhaust valve.. try the paper on the exhaust trick... anyway I ended up spraying WATER and cleaner into the intake manifold while the engine was running and up to temp.. I used about a pint of water and a can of AMSOIL cleaner - WD40 would also work and voila--no problem.. it seems to me that the sticking exhaust valve allows the exhaust manifold to get unduly hot and heat the fuel rail.. it worked for me though so good luck

 

Have you replaced any of the O2 sensors?

 

No I haven't replaced the o2 sensor yet. I was thinking the unburnt fuel from the misfire was setting off the o2 sensor. And I don't think it's a stuck valve it's a new engine with 2000 miles but I'm going to give it a shot.

 

Blew the paper out of my hand so passed that test. I'll try the wd40 tomorrow anyway just to rule that out

 

I have heat soak issues and nah. Go for the sticky exhaust valve and let us know how that works out for you.

 

What about that sea foam spray I've heard about? Would that work better than wd40 or amsoil??

 

For this application, no.

Seafoam is a dissolvent, destroys oil/gunk buildup. I would think in this case, to try and slime the internals, with an oil based based product. Think of it as running the engine rich.

 

Alright thanks for preventing me from making that mistake. A lot of people are telling me to replace the cam and crank sensors just want to say

Cam position synchronization sensor is new

Crank position sensor is new

Damn near everything is new.

I'm going to try the clean anything off the exhaust valves on Thursday and post the results Thursday night. Stay tuned

 

My 01 XJ had misfires about 6 years ago. Turned out to be low compression from exhaust valves. Head came off and it went to a machine shop. Problem solved.

There is a TSB. Says to pull the rocker arms and see if the valves have a bullseye or a line to determine if the valves are rotating. If not, it outlines a procedure to rotate them manually.

If you find the valves aren't rotating, you may want to try the rotate procedure and use Mopar Top End Cleaner before pulling the head.

 

Sorry to say the water and cleaner into the the intake manifold didn't work. she started to miss again after about 15 miles; but boy it ran well until then...I will continue to work on this and IF I come up with a solution I will post it...the benefits of retirement.....

 

Yeah didn't help me either I did the exhaust clean like was stated earlier and went and cleans the injectors and it died on me about 5 miles down the road. I managed to get a video of it dying and starting it back up with it being all fine again but I couldn't get the studder on video. It's less of a noise and more of a slam vibration from undernieth.

You'll also see in the first video right before it dies that it'll keep running but with only a couple cylinders running the other ones cease foreign completely leaving almost no power. I'm not entirely sure how that fits in with a normal missfire or if it is a normal misfire so any clarification from you guys would be welcome