Engine trouble

Drove up to the mountain today and started having engine trouble. Engine light flashing under load turns off when I Park it on the wide of the road. Still up here and don't have my codereader. No smoke out the back and all gauges are fine, but the motor temperatureseems crazy hot. I mean, the hood and fenders are hot, you can feel the engine heat like a foot away from the rig, but temp gauge shows smack in the middle. Electric fan is working. When on the pedal it sounds raspy, muffled, feels gutless. In case it matters, I have a cracked exhaust manifold because I have the usual ticking from that.

Any clues what this could be?

(don't say blown head gasket...don't say blown head gasket...)

Hello Fellow Oregon Jeeper!

I'm wondering if you have a blockage in your exhaust. The flashing CEL is very bad, indicating a catalyst damaging event is taking place. You mention muffled and gutless with low power.....I think you might have a bad cat or a blockage in your exhaust. Can you pull codes? If possible, pull them and post them here for additional help.

How are the fluids? Oil level and condition ok? Is it consuming coolant at all?

spinaldex said:

.......When on the pedal it sounds raspy, muffled, feels gutless......

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I second the suggestion you might have a clogged catalytic
converter. Those are typical symptoms for it. The cats will get VERY hot when this happens.

If I unbolt the exhaust at the end of the collectors/manifold so that exhaust can flow freely out, and the motor runs better, that would be about the best way to test it .. right?

spinaldex said:

If I unbolt the exhaust at the end of the collectors/manifold so that exhaust can flow freely out, and the motor runs better, that would be about the best way to test it .. right?

Click to expand...

This sounds slightly dangerous, especially in a non-ventilated area or near a fuel source.


The best way to test it would be an exhaust backpressure test. Or, the simpler option would be to get a good IR gun (about $30) and point it just before and just after the cat at operating temp. If you're glowing red hot before the cat, but more like ambient temps after the cat, I'd say you've got a blockage. You can also bang on the cat (when cooled down), gently, to listen for any broken substrate inside. The substrate is made from precious metals and produces the chemical reaction inside the cat to reduce emissions. If you hear anything at all rattling inside the cat, it's a definite goner.

As I mentioned though, pull codes and get them to us. Let the technology in your Jeep help you. I'll bet anything they're catalyst efficiency or severe misfire codes. Before dropping money on a cat, or doing tests you're may not be comfortable with, I'd try to get the codes. Most auto parts stores will let you pull them for free, or Harbor Freight has basic scan tools for like $40.

I'm always happy to help a local Jeeper and I'm in Beaverton so shoot me a PM if you ever need a hand. I've got a wireless Bluetooth dongle with a 40 foot range on my ASUS Windows tablet for OBDII and live data. It's a pretty slick setup to clear codes wirelessly. Whole thing set me back only a few hundred including the computer.

Yep. I have a bluetooth adapter and Torque on my smartphone, as well as a cable reader as well. I was up on Mt Hood camping for 4 days so I didn't have any of my stuff on me. Just got back in to town and used the code reader. The only code it is showing is P0306. I reset it, ran it again, and it showed back up instantly.

It does not blink the CEL unless under severe load. I can't simulate it in my driveway, it would only start blinking when climbing up the stretch to Government Camp.

The research I've done for the past hour shows that these are the most common steps performed to troubleshoot this issue:

1. Reset Code, Disconnect Battery, Reconnect, Run Vehicle. Does code return?
2. Bubbles in Radiator when car starts?
3. Replace #6 Spark Plug
4. Swap #6 & #5 Injector. See if the issue moves. If it does, bad injector.
5. Spray & Clean Throttle Body w/ Carb Cleaner
6. Spray & Clean TPS w/ WD40
7. Unbolt Exhaust & Test
8. Replace O2 Sensor
9. Swap coil rail & TPS sensor.
10. Crank Positioning Sensor
11. Cracked exhaust Manifold


Now, I already know I have a cracked exhaust manifold (shop who did my brakes mentioned it and I've been hearing the ticking from it for a couple months). I have to fix that at some point anyway, so I guess I could tackle that first? I was originally hoping to live with that for a few more months as its an expensive fix =(

Anything else you can suggest in terms P0306 errors?

Ugh. I don't know if my exhaust manifold is cracked or not because its impossible to see with it on the motor. Since its so common, I'm thinking it would be smarter to replace it with a new pair. I found a set on ebay, brand new for about $110 (2000-2001 have the two piece manifold). That sound like a good idea or should I pull them off first and inspect?

I would focus on the problem at hand. All 4.0 exhaust manifolds will leak, it's just a matter of time. Mine has leaked since the day I bought it 5 years ago but it's never caused me the issues you're describing and my short term and long term fuel trims are decent. I don't think a cracked manifold is causing your problems, so I would avoid dumping money into it until further testing. Your symptoms appear easy to duplicate, which should make diagnosis much more simple.

Sounds good. I'll work on spark plugs, injectors, cleaning the TPS & TB, and the rail to start. If no luck, then its on to the CPS.

Also, for a clogged catalytic converter, easiest would be to drive it down to a local exhaust shop and have them run a test right? I just recently had a cat back replacement put in (2 weeks ago) because my muffler had a big hole in it (oops .. *cough*).

6th cyl spark plug was covered in oil. What does that mean?

Also, I cleaned the rail and TB, dielectric greae and all new plugs. No change.

Its sluggish, maybe 1/2 as much power as normal. Still complaining about cyl #6 but only under heavy load, when I stay off the throttle its more or less ok.

Made sure the gas is fine by draining and refilling with premium.

Also, I ran seafoam through it to clean the fuel system.

Tried to unbolt the catalytic convertor but the bolts are all seized. Thinking about spraying PB Blaster there and see if I can gap it before the Cat and see if it acts better. That would indicate a blockage of some sort.

Pretty busy this week and then going camping so I'll have to work on this next week. Going to bring it to an exhaust shop if I can, eliminate the cat as being a problem.

If that isn't it, then I'm running out of ideas. Some say the rail could be bad on one port if that cylinder is not firing, but I would like to know how to test them without just spending $150 on a new rail ... Or, others say the injector could be bad, but I'm also not sure how to test that without spending a bunch of money.

Any suggestions?

Is the #6 plug wet or dry?

If the plug is dripping oil then the cat was probably trying to deal with it.

I'd do a compression test before buying parts.

The back half of the motor has a lot of wet oil so I know I need a new valve cover gasket. It's quite possible that when I pulled the spark plug I accidentilly got oil on it. I'm going to spray it all with engine cleaner and then pull the new one to be sure that there's oil on it on the inside. If its the outside its just a gasket .. if its the inside, I'm probably screwed because it just became expensive.

Now, here's a question ... since this is a 2000 with the solid coil rail, how do you do a compression test while being able to keep all the other plugs connected?!

Compression test is not done with the engine running.

Remove the coil pack, all plugs, and wire the throttle open.

Good idea to remove the fuel pump relay also.

Then you put the compression gauge on cyl, crank it over 4-7 times (starter) and take a reading. Repeat for cyl 2-6. Be consistent in the number of cranks.

Best on a warm/hot engine.

Thanks! Will do.

I haven't had the money to do much but here's what I was able to accomplish since I created this post.

I swapped out the coil rail for a working one and got a set of new NGK plugs. Replaced the TPS and put in new 4 hole injectors. Still acts exactly the same.

Basically sounds a little like a rough running, very big lawn mower. I took it for a drive and recorded it on video. Hoping the distinct sound might spark some ideas.

My next step, probably next week is to do the compression test.

Will post the video tonight after dinner.

The compression test is a must.

You could also try removing the up stream oxygen sensors before the convertors.This produces the same effect as removing the catalysts.

https://www.youtube.com/watch?v=M-4pkVVTI98&list=UU37gfCLPXPpl50OJpYKFNdg

It might be a bit hard to hear. It sounds throaty, has a strong vibration and shakes the rig a lot more than usual, and has a weird wop/wop/wop/wop that just sounds off.