Started out I had no heat with these record breaking sub-below temperatures... Changed out the thermostat a while ago to avail (haven't had heat for 2 years). Had a heater core flush.. again... worked for a day. Had it scheduled for maintenance (had a bunch of stuff needed done).. U-joint, Oil pressure sensor had them re-flush and change out thermostat.. Overheated later that night.. check gauges lite came on.. reflushed core again. Check engine came on later that night. Had the radiator changed out for NEW, had the head fleuxed and shaved to 8/1000's, NEW gaskets, had a NEW thermostat changed again and the water pump checked (OK), had the fuel injectors checked (1 changed out for NEW) and all the O-Rings replaced, NEW coil rail installed, had NEW cam sensor and crank sensor installed (Mopar no after market) ran great for 2 days... 10 miles 1 way to work. mostly highway / over 50mph... trouble always starts at night... (xj is warmed up for a few minutes) drive about 13 minutes to toll I slow down to drive through and as soon as I slow down or proceed to accelerate to get up to speed... Misfire and check engine light comes on.... or as I slow down to take exit off of highway... 35mph... check engine blinks 3/6 times and stays solid yellow... This has happened for the whole month of Feb and now into March! She has spent more time in the shop... have spent over $3k on trying to fix her and I'm starting to run out of $$$... Kept coming up with a misfire cyl 1 code... had the fuel inj and plug swapped out to see if that was the problem... this last time shes been at a sleepover at the shop for the weekend and havent gotten the latest diagnosis... She has a newer engine... replaced approx 4 years ago...... I have read a ton of stuff all over the net/youtube... could be cracked fly wheel, throttle position sensor, O2 Sensors, Bad CPU... any help on diagnosis... really running out of $$ at this point!!! Any help greatly appreciated at this point!

 

Before you spend any more $$$ do a compression test, motor may be kaput.

 

Compression test was done... all is great!... Heard back from shop... looks like I now need a new fuel rail... causing sediment to accumulate at the injectors causing misfire... Keep your fingers crossed this solves my problem... Hope I could help anyone with same issues... Will keep you posted if this does the trick.. It's the last $300 I want to dish out!!! till inspection time... and a new alignment...

 

New Fuel Rail and New Injector 1... Runs like a dream! So Smooth!! No more misfire! The rail was filled with rust and sediment.. every time it got flushed more and more sediment would clog Injector 1... causing the misfire... including every time I slowed down... then accelerated. Like on highway at a toll.

 

Im glad it finally worked out for you, I would've been pissin' my pants by this time if I were you haha

 

Ya... all because I wanted heat... what the H was I thinkin? Should've just stayed cold!... but now it's like havin a new Jeep!!! It was worth in ... but now I have to work a Sh@# ton of overtime to pay for her!!! Gettin ready to do body work and next week finish it off with an allignment after installing new tires and rims... the $$$ just never ends! I keep payin and payin... but she is worth it!! will post before and afters next week!!

 

Back in the day, I worked at a Dodge dealer. I had a Neon that the inside of the fuel rail was coming off. Looked like paint flaking off, stopped up the injectors. New rail, new injectors, problem solved.

Glad you got it figured out......RR

 

Did you ever switch the injectors to see if the misfire moved with the injector? I just find it hard to believe that the sediments always ended up behind cylinder 1 injector. I've also been chasing a cylinder 4 misfire but in my case the misfire is always on the same cylinder no matter which injector is in there. You might have just had a faulty injector.

 

It always came up on injector 1... I had inj 1 replaced... code came up inj 1. I moved the injector around and it still came up 1... the last time it was so clogged after the rail being flushed that inj. 1 couldn't be cleaned and had to be replaced again. Not to mention even after the flush... It was still pushing sediment through! It was definately the rail!