Blinking check engine light - Misfire

Hey guys, new Jeeper here.

I have a 2000 Jeep Cherokee sport that I traded my Subaru for back in November. I'm kind of regretting it now though :X

Everything was fairly ok until recently when I added an AEM air intake. Now I get a solid and blinking check engine light, stutter, rough cruising, no power. Prior to this I'd get a small stutter occasionally on the freeway.

Anyway the code is reading misfire on cylinder 5. P0305 I believe.

Since getting it I've put on in the last 5 months:

-Champion double platinum plugs
-Rock auto coil pack
-Mopar crank position sensor(after cel)
-Ford XRE-something 4 hole injectors
-Mopar cam sensor (after cel)
-Serp belt
-Flowmaster muffler/magnaflow cat (put on after cel)
-Both o2 sensors NGK (Federal emissions)
-AEM air intake (major problems after this)

Previous Owner said he replaced the TPS and Battery(cheapo Walmart one)

Engine grounds look ok, battery leads cleaned (replacing in future)

Reseated coil pack and cleaned plugs. (Swapped the one for cylinder 5 also)

That pretty much covers ignition system, correct? I might be missing something...

I know people are going to chime in and say take off the intake, which I would/will....but there's still an underlying issue somewhere without it.

In the stock form, it did stutter occasionally on the free way (or when it was warmed up for a decent amount of time, no CEL though) this is both with and with out those new parts.

I'm currently thinking it's my fuel pump not delivering the PSI the truck wants since I about doubled the air flow going in and out essentially. Or maybe a bad valve?

I'm going to test fuel pressure today and double check it.

I have a bored out throttle body coming tomorrow also. (Not that I'll be able to enjoy it)

Hopefully someone can chime in something I might've missed. Thanks for any and all help...

Since it is saying only one cylinder, trouble shoot things that effect that cylinder only. What do the plugs look like? Do a compression test both wet and dry. Do a leak down check.

It could be a clogged injector. Run a can of BG44K through the gas or at least a bottle of Chevron Techron. Another alternative would be to swap that injector to a different cylinder and see if the problem follows the injector.

I'm mainly a Renix guy. Does your rig have a coil per cylinder? If so, swap the coil to another cylinder. If it has spark plug wires, pull that one off and measure it with an ohmmeter. You could have arcing. Start it at night in a dark place and look for arcing.

2000 has coil pack. Like one of the things old man said though, check compression. If your valves and rings aren't sealing, the other parts don't matter. Always check compression before pouring money into other parts. If possible, check before buying vehicle.

Have to ask, is the engine consuming coolant? I had a '97 that was tossing misfire codes for one cylinder and when I pulled the plug, I could actually see steam coming out of the plug hole. Turned out to be a blown head gasket allowing water into the cylinder that killed the firing of that one cylinder.

Not saying that yours is having the same isue but, it may be worth looking into...

When did you install the injectors?

Injectors I did a month ago? They worked great..until I put this intake on.

But still had a small stutter at highway speeds, heated up.

I have been fairly vigilant on checking the coolant and seems ok, no oil, but that's a good possibility. I will pull the plug after being fully heated up just to see.

I'm just hoping it's not the rings. Jeep seems to if been well cared for so hopefully just a valve, or HG, or fuel pump. I really don't want to do a motor swap in 10 degrees

I will get compression test results and report back.

Thank you guys

Ok update!
Just finished the compression test with O'Reilly's rental kit.

Results:
1 = 155
2 = 160
3 = 155
4 = 165
5 = 155
6 = 170

I have to say first I had a hell of a time getting those remotely hand tight due to the tools design. But even with those numbers they look good?

BUT! The spark plug for cylinder 5 was awful! 6 wasn't great either.



1 is the far right, 6 being far left.

Close up of 5



I installed these plugs within the last 4 months.
What would foul it out that quick if my compression is good?

Starved for fuel?

old_man said:

Another alternative would be to swap that injector to a different cylinder and see if the problem follows the injector.

Click to expand...

This is exactly what I would do. You need to rule this particular injector in or out. Your compression numbers are fine.

Swap and see if the misfire follows. You also can test injectors for resistance, but swapping is the best way to go. Just because injectors are newer doesn't mean they can't fail.

Gotta do this before moving on.....

The injector isn't starved of fuel. Its oil, coolant of fuel on it. Its wet. I would rent a coolant pressure tester kit, pull that plug and pressurize the cooling system. Its a start but not 100% conclusive as it may need to be hot if there is a HG leak. You could also see if there are any bubbles in the radiator neck while running. Do you notice any smoke from the tail pipe? I would also move the #5 injector to another position and see what happens. If the injector has an issue the misfire code will follow the injector as well as the plug on the cylinder having the same issue. Does that plug smell of anything, coolant, fuel, etc? When did the issues happen as far as the plug change goes? Its generally recommended to use NGK copper plugs on the 00+ engines.

^ I've' always been told to use Champion Platinum plugs on the Jeep 4.0ltr coil pack systems. It's a waste spark design and coppers will burn up on them...

I'll swap the injector, clear the codes and see. I did test the fuel pressure and it held a 49psi pretty well.

@Talyn there is only the white smoke when first started up(like every car I've owned), nothing that's alarming to me. I'm familiar with blown HG as I fixed it in my Subaru before trading it. Once warmed up, exhaust is dry and hot, no coolant or burnt oil smell.

If the injector turns up ok I'm just going to take the head off and go from there.

That's what I read also scoobyxj!

I took copper champions out of it, they had been in there about a year and looked weathered.

Ok swapped injector #5 to #4 (Tried to go farther in firing order)

Touched battery cables, reset PCM. I let it idle for about 5 minutes, got a CEL, I shut it off to look for something in the house.

Came back out 5 minutes later, started it up, CEL gone, drove around for about 45 minutes with a carwash, freeway driving etc.
Could not get another solid CEL, but I got a few occasional blinking CEL's.

Went back to O'Reilly to turn in the compression test kit and fuel test kit, borrowed their scanner and got P0122 (TPS low voltage or something) and P0304 Misfire Cylinder 4

So it looks like it's a bad injector. I will get a replacement and update on what happens.
For the record, the part number for the injector is Ford/Bosch XF2E-C4B - which is what I read is appropriate for 2000 and 2001 XJ's

scoobyxj said:

^ I've' always been told to use Champion Platinum plugs on the Jeep 4.0ltr coil pack systems. It's a waste spark design and coppers will burn up on them...

Click to expand...

I don't know where that info came from, but its wrong. The wasted spark system won't burn up the copper plugs. NGK Coppers were OE for all the 4.0Ls w/ coil rails. Must be some crap from CherokeeForum or JeepForum. I still run NGK coppers on my stroker, but a colder heat range.

rogo.xj said:

Went back to O'Reilly to turn in the compression test kit and fuel test kit, borrowed their scanner and got P0122 (TPS low voltage or something) and P0304 Misfire Cylinder 4

Click to expand...

Sounds like it is definitely a bad injector.

So another question, during this trouble shooting I ended up putting the bored out throttle body on, and now am getting the TPS code throwing...one thing I encountered when swapping the TPS is I wasn't sure if there was a specific way of putting it on?

I definitely didn't get that code prior to swapping it over, anything I should look at?

@Talyn...any recommendations on which NGK plug?

Thanks again for all help for anyone who chimed in.

There is a correct way to put the TPS on. You need to seat the throttle shaft in the TPS, then rotate it so the bolt holes line up. If you forced it, it is damaged. However, you would have noticed it going together poorly.

The NGK plug is ZFR5N PN 3459

Talyn said:

I don't know where that info came from, but its wrong. The wasted spark system won't burn up the copper plugs. NGK Coppers were OE for all the 4.0Ls w/ coil rails. Must be some crap from CherokeeForum or JeepForum. I still run NGK coppers on my stroker, but a colder heat range.

Click to expand...

Nope...

http://www.aa1car.com/library/sparkplugs_for_dis.htm

http://shop.advanceautoparts.com/o/article-spark-plug-basics

http://www.youtube.com/watch?v=ekCpGSR4oMA&feature=player_embedded

Wanting to educate myself on this "reverse spark polarity" thing, I went to the NGK site. Coil rails like ours should use dual exotic metal electrodes.

When I had a similar issue w/my '01 XJ it was a bad Coil Pack. When I swapped in the new Coil Pack it fixed the issue. Since then I've replaced the Coil Pack w/a different set up... Viper Coil / Wires and like it MUCH better.

I also agree w/ Talyn... use the NGK Copper plugs. To be hones I've never had long-term good luck w/the super-duper-exotic plugs. NGK Coppers are the most consistent and best I've had for the past 20 years... in all my different vehicles. They are a replaceable part and I don't believe the hype of lasting 100K miles, etc... Plus they're a LOT cheaper than the Titanium/etc plugs.