Hey everyone, yesterday while driving back home, stopped by the store to get something to drink, came out and started the jeep - misfire. This happens often, I know its the heat soak, and its usually fine within a minute or two, however this time it didn't calm down. Check engine light started flashing on the (short) drive home and it ran rough. When I got home, I disconnected the battery (not smart, now I don't have codes) to work on it, but it got dark quick so I couldn't.

This morning, started it up, ran rough at idle and low speeds, but the drive to work it drove perfectly fine. So it's only bad at idle and very low speeds < 10.

Any idea what it can be? The drive to work was maybe 1.5 miles and the CEL isn't on again so I haven't plugged in a scanner as of yet. Just wanted ideas before i start troubleshooting.

Summarize: Rough idle and at low speeds, runs fine when moving. (Coil pack was changed in August)

Thanks everyone.

Sounds like a vacuum leak. I'm new to Jeeps so maybe someone who knows these engines better might chime in on most likely place.

Maybe aacuum leak, or possible dirty or malfunctioning IAC (Idle Air Control). Often all that's needed is to clean it up. Sometimes it needs to be replaced. It's an easy job.

To find a vacuum leak, spray WD-40 or similar flammable product around the suspected leaks, and listen to the engine. If you spray a flammable liquid and it gets sucked in, the engine RPM will increase. Now you know where the leak is.

Yep - my thoughts exactly. Both easy jobs mate - couple of hours max - start with vacuum leak as it's easiest. Presume she's been regularly serviced and that the HT leads were replaced with the coil pack or around the same time?

Disconnecting the battery on an OBD2 won't clear the (flash memory) trouble codes.

Get an O'Reillys to pull the codes - or better yet your local NAPA Monday AM. Those are the only places I do business with. Most other places won't even tell you the codes if they pertain to 'emissions' codes.

Well, heres an update
I scanned it, got a misfire on cylinders 1 and 4.

I changed the coil rail, spark plugs, and all 6 injectors, and now I am getting a code for cylinder 1.

Changed the pcv valve, and I don't know what to check for next. I got a compression test and it all checked out fine (I didn't do the test myself, I had it done because I don't have the tools)

Any suggestions? thank you

Stop firing the parts cannon. It's an expensive and frustrating way to fix a car.

Have you tried any of the suggestions already made?

I actually had the parts already because I was going to do a tune up once the weather got warmer, with the exception of the coil rail, but I had changed it in August and it was still under warranty so I just grabbed another one.

I did not get any email notifications for the post for some reason, so I will be checking for a vacuum leak as you suggested. Any tips on where to look or to make things easier?

Thanks

Give this a try... I did with my '98 Limited. I chased a misfire for over 2 years off and on. Ended up being bad injector wiring to #3 and #5 - had to buy a used harness. Changed it... problem solved. I think I paid $100 for the harness that had low miles on it. Gotta look on your harness at the PCM and be sure to get the exact part # replacement so that all your stuff hooks up properly. A PITA to unsnake the harness... but take it from someone that threw $$ at it and did nada... this solved my problem. Try what ya wanna first, but don't forget about wiring... it can drive you bat **** crazy

Nate

May wanna try some BG 44K valve cleaner first. Read many posts about carbon building up on exhaust valves causing them to 'float' and not seal fully which can give a 'misfire' code. This stuff is used by dealerships. The direct injection cleaning is done by certain shops because it is done through the fuel rail. Or, you can use the 'in-tank' stuff first which does not require anything except dump into gas tank and drive it out.

https://www.bgprod.com/catalog/gasol.../#bg-product-4

Hmmm. Not really. Just start somewhere and keep working along. Keep track of where you have been. There are a lot of vacuum hoses.

Here's a random thought - take a picture or two of the engine bay, pop it into Paint (or similar), highlight all the vacuum possibilities, and print it out. Then you can use a marker on the picture to keep track of where you have sprayed.

This is a good test because it's really cheap (a can or two of WD-40) and very important.

BTW, it's either tjwalker or cruiser54 who recommends the BK44. That's not a bad idea, too. Their advice carries a lot of weight around here.

And... I will also tell you in advance... you can not rewire the injectors manually. I had that bright idea before I purchased a used harness. I swear Chrysler either glues or varnishes those bundles of wires that feed through the injector rail. I could not separate them to save my life. Jus a heads up... been there... done that

Compression test.....Same thing happened on my 00, ended up being a stuck valve. Could be another issue with the head as well

I haven't had a chance to check vacuum leaks yet, but I did check the injector wires and they all are okay. Combination of work and school, you know how hectic it can get. But thank you.



I got a compression test earlier (I didn't run the test myself) and was told its fine. Head issue is also very possible, considering its an 01