Misfire Problems

On my way to work cruising the hwy the other day the Jeep started backfiring and sputtering. I then proceeded to pull over and it stalled out. I got it started again but as soon as you give it gas it would backfire than die. Then finally it wouldn't restart anymore. I ran the codes by key-click and 43 came up, the one for misfires.

I had the rig towed homw and ran the codes with an OBDII reader and they were P0300 (random/multiple cylinder misfire detected) and P0351 (ignition coil A primary/secondary circuit malfunction).

This problem is on a 96 4.0L AW4 w/ 160k. The plugs, cap, rotor, coil were all changed about 3-4 months ago.

I tried searching and didn't really find anything close to my problem, at least code wise. I remember reading somewhere that you should have a constant power to the plug that goes to the coil when the key is turned and a pulsating ground. I checked the plug with a 12 volt light and there is a constant ground to the terminal closest to the block but there is no power (hot going to the other side at any time).

Is there a coil controller somewhere or is it in the ecu? Is there a way to test the coil itself? Hopefully you guys will give me some good pointers. Thanks.

-Mike

Upon taking a closer look at my rig I noticed my throttle body had a crack going across the front. I then proceeded to take it off and took some PICS.

-Mike

That's one hell of a crack. You should be able to fix it with JB Weld. Don't know if that'll also fix the backfiring problem though. This is one of those chicken and egg situations (backfiring and cracked TB) so it's only by trial and error that you'll find out if the JB Weld fixes the backfiring as well.

Fixed the crack temporarily with JB weld. But this did not fix my no-start/backfiring problem. Is there a way to check the coil and the line going to the coil? Is the controller for the coil in the computer or is it seperate someplace? My codes that came up WERE P0300 and P0351. I erased them with a code reader and now they don't come up but it doesn't fire up. It just turns over. So evidently I am not getting spark from the coil. I know I am getting gas because I can hear the fuel pump. Thanks in advance.

-Mike

I would guess the throttle body cracked because the engine misfired out the throttle body and blew it apart. As for why... the usual culprit it's the CPS isn't it? Going out it causes timing type problems, and dead causes no-spark.

Just a guess...