4.0 CEL, random cylinder misfire, cyl 2/5 misfire, and a loud engine noise at accel.

Aran · 03-08-2009, 01:49 PM

Wow, I need a longer title line.

This is a '00 XJ with the 4.0.

I made a thread ages ago for the still-unresolved misfire CEL codes, but I can't seem to find it.

Anyhow, it's added in a new problem.

Now, when you put pressure on the accelerator, there's a vibration in the pedal and a loud metallic noise, a cross between a clang and a quiet gunshot sound, every few seconds. With the hood up and using the throttle on the engine itself, it sounds like it's coming from somewhere under the airbox, though it's not causing any sort of problems with the engine running, it's still sucking air hard, and the only issue is that the misfires are putting it into limp-home mode so it makes acceleration a bit difficult.

Unfortunately the weather and my work hours have made it too inconvenient to get under and look for any issues that might be causing the sound. My thought was maybe the exhaust header has a leak, as it's a similar sound to what my Probe makes with the EGR hole on the exhaust header being unplugged. It's not quite like something's banging, just an unrestricted kind of sound.

It's hard to describe, I guess.

At any rate, is there anything any of you have encountered that would give me an idea where to start on any of my issues? I know that there are platinum plugs in it, which may be part of the misfire problem from what I've read. I don't have a socket that can get down into the holes to pull them and replace them, unfortunately. My sockets are all too big to fit down in. That's on my list of things to do.

It's at about 185k miles, the oil's been changed every 3-5k from what the previous owner told me, and the only records I have on it are from when it had an alignment at 170k. The air filter looks clean, with nothing blocking it. It still runs perfectly, pulls hard, gets decent gas mileage, etc., aside from when it knocks into limp home mode and the CEL comes on, seemingly at random.

It can go for a week or two before having another spat, then do it constantly over the course of the next day, having to have its codes cleared to get it to stop for an hour or so.

Thanks in advance

Aran · 03-10-2009, 08:34 AM

Anyone?

Pretty please?

I can't afford to take it to a shop to get it looked at

jeeptown · 03-10-2009, 08:46 AM

when was its last tune up? Maybe you have a bad ignition wire or plug.

Arkansas91XJ · 03-10-2009, 09:09 AM

Check for any blown fuses, my buddy's 99 was throwing MAP, IAC, O2 codes, running rough and everything, after resetting the comp it would be ok until a couple hours later, after replacing the MAP sensor and it still throwing the code for it, he happened to run across a little 10 amp mini fuse under the hood that was blown, popped in a factory spare and all problems went away!

**XJH-007** · 03-10-2009, 09:54 AM

Hmmmmmmmmm, lound metallic sounds or a gunshot?!? WTF? You sure it's not like a driveby going on behind you??

So hows about this one........

If it still runs decent and has these misc. issues.....look into the throttle body and it's components. I've never heard of the sounds you talk about but I suppose the IAC motor could be really messed up.....that's the ONLY thing directly connected to your pedal. Maybe it's jerking the throttle, causing a backfire(gunshot)the CEL code and making your noise....

Amadeus3 · 03-10-2009, 11:34 AM

What about an exhaust or intake manifold leak? Exhaust would be my bet, especially with the noise you are describing and that could throw the random misfire code

rtrimarc · 03-11-2009, 03:19 PM

I had similar issues, turned out to be my fuel rail was corroding from the inside and kept messin' up my fuel injectors. Eventually it would only run on 4-5 cylinders. been fine since changing the fuel rail.

Good luck.

Rob

Aran · 03-15-2009, 02:42 PM

Well, that's quite the laundry list of things to look at.

I guess I'll start from the easiest stuff and work my way up.

Thanks for the ideas guys!

I'll let you know if I come to a solution

XJ Jay · 03-15-2009, 04:06 PM

sounds like its midfiring and leaning out and back fire through the intake.

but my recomendation would be to bring it to a shop to at least diagnose it. your gonna spend all kinds of cash chasing your tail and chucking parts at it, when you can pay a pro a hour or two of labour to tell you exactly what it is. but if i had to guess i would say cloggeg injectors

**filluptrk** · 03-16-2009, 12:11 AM

The rail has 3 coils, with waste spark ignition and one of the coils fires cyl 2&5. It would seem then that either the coil rail has a weak or faulty coil, or the perhaps the rail connection is not great. In addition the PCM controls the drivers for the coils. You might try pulling the connectors to the PCM, and reconnecting them. I've read that you should pull the negative battery cable before doing this to avoid damage to the PCM. Often a disconnect and reconnect will clear a poor connection. Phil

**tjwalker** · 03-16-2009, 07:22 AM

Posting the exact code numbers is always helpful.

You might want to try swapping hardware associated with the misfiring cylinder(s) and see if the code follows. Fuel injectors, coil rail would be things to swap.

colt933 · 03-16-2009, 10:53 AM

Quote:

Originally Posted by tjwalker

Posting the exact code numbers is always helpful.

You might want to try swapping hardware associated with the misfiring cylinder(s) and see if the code follows. Fuel injectors, coil rail would be things to swap.

Fuel injector - yes, certainly, swap with a known good firing cylinder and see if the code follows the injector.

How would you swap a coil rail without buying a whole new one?

**filluptrk** · 03-17-2009, 12:21 AM

You might try first pulling the connectors on the injectors on 2 & 5. You can spray some contact cleaner if you have some, but if not plug them back on and wiggle them around while you reconnect. This worked for me with injector problems on 1 & 2. Cleaned them up put some dielectric grease on injector pins and ran some Techron thru the system twice, and no problems since. It is a lot easier than swapping injectors. Phil

**tjwalker** · 03-17-2009, 07:22 AM

Are the plug boots firmly and completely seated on each of the plugs ? Easy stuff first. Test the coil rail with an OHM meter. You should have between 250 and 1000 ohms. The coil rail fires the plugs in pairs, so you may have to test coils packs similar to this procedure

Pin 1&2
Pin 1&3
Pin 1&4
Pin 2&3
Pin 2&4
Pin 3&4

If you suspect a coil rail, a salvage yard is a good place to source this part to swap in inexpensively, especially if you're not dead certain of the cause.

03-10-2009, 09:54 AM	#5
XJH-007 I drank what? Join Date: Mar 2005 Location: Morrison, Colorado Posts: 4,674 Profile Gallery Classifieds My Jeeps	Hmmmmmmmmm, lound metallic sounds or a gunshot?!? WTF? You sure it's not like a driveby going on behind you?? So hows about this one........ If it still runs decent and has these misc. issues.....look into the throttle body and it's components. I've never heard of the sounds you talk about but I suppose the IAC motor could be really messed up.....that's the ONLY thing directly connected to your pedal. Maybe it's jerking the throttle, causing a backfire(gunshot)the CEL code and making your noise.... __________________ Scott-Crawlorado Native I have an addiction..... 00' XJ_T-n-T Y-Link/6" RE_OME's_33" KM2's Tera 4:1 / 4:56's_Elec. Locked D44 84' CJ7 4"BDS 33's **02 WJ Overland

03-11-2009, 03:19 PM	#7
rtrimarc Registered User Join Date: Dec 2005 Location: Saratoga County, NY Posts: 94 Profile Gallery Classifieds My Jeeps	bad fuel rail I had similar issues, turned out to be my fuel rail was corroding from the inside and kept messin' up my fuel injectors. Eventually it would only run on 4-5 cylinders. been fine since changing the fuel rail. Good luck. Rob __________________ 2009 Grand Cherokee Laredo “Not responsible for misplaced property, political unrest, coaching decisions, bad punctuation, misspelled words, the economy.”