Back firing bad!

Had a buddy bring over his 97 Cherokee 4.0 auto 2wd. It's been having a lot of trouble. Put my scan tool on it and I got

P0304
Cyl 4 Mis
P0303
Cyl 3 Mis
P0302
Cyl 2 Mis
P0300
Random Mis
P0135
Ox sensor heater Bank 1 sensor 1
P0204
Inject 4 open
P0201
Inject 1 open
P0203
Inject 3 open

Viewing the live data the down stream o2 is fluctuating above .8 constantly and the cat is glowing orange hot after a few seconds of running the motor. It's backfiring at idle constantly. It's running like its down a few cylinders as well. Really ruff idle. Every cylinder is getting spark. The plugs look really black on the electrode. And the ceramics are all really red. I'm thinking it's timing and injector related. Ill be glow plug checking the injector harness this week and working that way. The map sensor seams to be working properly. Just wondering if anyone had any other ideas to look at. Live data shows the timing at about 15 at cold idle and about 47 at 2500.

A bad cat? Does it rattle when you "tap" it. If the cat is clogged it'll glow like that...it will also cause way too much back pressure. Glow plug? Is this a diesel?

The 3 main culprits I would look at are:

Clogged cat (pre-cat?) or disintegrated cat...clogging the muffler?
Bad UP stream O2
Messed up distributor have you had the dizzy out? Looked into the dizzy?. Rotor seated correctly? Any play in the dizzy shaft?

I would check to see if TDC is still TDC for #1 cylinder and verify the dizzy is pointing at #1 on the cap. Then check compression on all 6 cylinders.

Do both of these BEFORE you run the engine again, or you risk ruing many parts very quickly!!!

So last night I pulled the cap and rotor appart and checked it out. Looked to be in good running order. I also swapped the pickup coil out. It ran worse when I put it all back together. I'll be checking TDC tonight and check the injector harness out as well. The funny thing is I test drove this thing before he bought it. It ran like a champ. And it's just steadily been running worse since then. Just want to figure it out soon so he doesn't get too discouraged with it. He is just getting into jeeps and off-roading.

Bucking, stalling and backfiring are O2 sensor symptoms. Since O2 sensors have direct input to the fuel trim, one might suspect an issue there. You obviously have excess fuel passing through to the exhaust.

What is the age and condition of your O2 sensors ?

Have you tested the injectors for faults or failure ?

This statement "cat is glowing orange hot after a few seconds of running the motor" says the problem is immediate, and not an O2 sensor issue to me. The engine is in open loop and not using the O2 sensor at that point.

Sounds like timing changed jumped or worse to me.

I also think the timing chain is suspect. Check the TDC and timing mark, and see if it is off. Then a compression test is a great idea. If all cranking pressures are within 10 percent, it should be an easy fix. If all are below 120 psi, and one or more is below 100, get ready to take the engine apart...

Ok so just to update. Took another crack at it on Sunday evening. Found the source of the backfiring. Some how the five and six plug cables got swapped. The cat is no longer glowing a d it's starting just fine now. Still is down a cylinder though. Did a compression check and all is good there. Checked the injector harnes and all are working properly. Checked the injectors all are working properly at least they are clicking when I give them power. But still number four wasn't firing. So I manually fired the injector and wow huge difference. Obviously not perfect but you can tell that cylinder is not getting fuel. So I back probed the number four injector plug and it is working properly. Don't know what to do from here. The injector only works if you manually fire it but there is nothing wrong with the harness, plug, or PCM.

1-5-3-6-2-4

Worth memorizing.

15 too young, 36 too old, 24 just right...

I'm going to staple it to his forehead.

lol
Its witten right on the intake manifold for a reason.
Dont feel bad. I didnt know the order so I found it on the manifold and proceeded to hook it up in the right order, but backwards (clockwise). Intake backfire and ended up blowing my intake gasket out worse than it was.

*89Laredo* said:

Its witten right on the intake manifold for a reason.

Click to expand...

Oh, I thought that was the part number...:twak:

I asked for the #153624 manifold. They didn't have it.

...but seriously folks, that's has been the same firing order on every 6 cyl engine I'e ever had. I thought it was universal. Maybe no, maybe yes.

I had a dodge avenger v6 do this to me, random misfires and a glowing cat.. It was a faulty ASD relay go figure lol

Haha. Yeah. Wasn't sure of it either so I just pulled the hood on mine and checked. I have seen that on the intake though. Never thought to use it. Haha

Yeah the order is the same but I did find out there are a few different orientations of the dist depending on model I think.