I recently changed my spark plugs. Since then my car has been misfiring, shutting off randomly, shaking, and shifting really hard! Please help!

 

If it wasnt misfiring before and started to misfire right after, obviously it has something to do with the work you did. Pull the plugs and check your work, you probably over torqued and cracked a plug . Did you use a torque wrech and go to only 20 ft-lbs or just crank on them with a rachet?

 

I just cranked on them with a ratchet. But I took it to the dealer and they took out the spark plugs and put them back in. So they basically went over my work. I was thinking it was the coils so I just ordered six new ones. Can a bad coil cause these issues?

 

Yes a bad coil can cause misfire, but if it wasnt misfiring before you changed the plugs it most likely isnt the coil. Plus a bad coil would throw a code. Coils are very easy to check, just hook a ohmmeter up and test continuity between pins 2 and 3. Also the coil pack will usually blister if it fries.

Look for any oil in the spark plug tubes, probably cylinder 6.

 

I will try that. But what I was thinking was that when I installed the spark plugs wrong the first time it may have messed up the coils. The codes I get are P300 and P1574. Any help with those codes?

 

P300 and P1574. Any help? Please!

 

P1574 is a problem with the vehicle speed sensor. Your ECM compares two speed signals (one from TCM and one from your combination meter) and give an error if they do not match. Means either one of the signals is bad, harness has a short, or ECU has an error. I have no idea why you are getting this code, it has nothing to do with the other issue. A ECU reset should hopefully clear it.

P0300 is multiple misfiring on 3 or more cylinders. This easily explains your issues. Something is defiantly wrong. Check the following:
-First, recheck your plugs for cracks and verify gapping. Plugs are preset but could be off. Get a gap measurement tool from autozone for a buck and verify all are .044".
-Second, check for any blisters on the coil packs.
-Thrid, check for oil pooling in the spark plug tubes.
-Fourth - verify you connected the cylinders properly. 4/6 are easy to swap.
-Fifth - check your intake gaskets for vacuum leaks.
-Sixth - check your coil grounds are all tight.

Remember to reset your ECU too.
-turned ign. to on & wait 3 seconds
-press and release gas pedal 5 times within 5 secs.
-wait 7 secs then press and hold gas pedal for 10 secs
-if you did it right, the check engine light starts to blink to let you know you are in service mode
-release gas pedal
-press and hold gas pedal for 10 secs to reset ecu memory
-turn key to off, then start car

 

I will definitely be doing these things. Thank you so much man!! You have been great! Is there any other way I can contact you beside this website? It seems like u know what your talking about.

 

Zoosk.com


He resides on the jeep forums, iirc!

 

Also... I notice that everytime I get in my car I see that my temp gauge is all the way down. Then when I start driving it rises to mid range. Is that normal?

 

Also... I notice that everytime I get in my car I see that my temp gauge is all the way down. Then when I start driving it rises to mid range. Is that normal?

 

a common problem when swapping spark plugs is people install the coil packs for #6 and #4 in the wrong places. Those are the rear 2 on the driver's side. Check this also, if you haven't. It causes a P0300 when it happens...also sounds completely different in exhaust.

 

Okay. Will do. Thanks!

 

Every car does that when it hasn't run for a while