Catalytic Converter - could it be bad...?? - JeepForum.com
 
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post #1 of 7 Old 07-07-2020, 05:33 PM Thread Starter
Fab5father
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Catalytic Converter - could it be bad...??

2004 Grand Cherokee, 4.0L (rebuilt engine with less than 500 miles on it from S & J Engines out of Spokane. Engine is warrantied for 7 years/100000 miles) came with new fuel pump. Items that have been replaced: Crankshaft Position Sensor, Idle Air Controller, plugs, front O2 sensor, (back O2 sensor has been tested [by certified Jeep mechs] and is known good).

Issue:
Engine will idle rough and eventually die. Sometimes given O2 sensor codes, sometimes giving no codes.

Could the catalytic converter be bad and causing this issue?

I am at a loss!

Thanks,
Steve

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post #2 of 7 Old 07-07-2020, 06:03 PM
speednjay
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Have someone rev the engine while you feel how much exhaust is coming out of the pipe. Careful hot. Either it’s plugged and you’ll barely feel any exhaust Blast or it’ll blow out freely .

Do the 4.0 have a mass air sensor? Check that if it has one, And then listen for Any air leaks. Maybe they didn’t hook up a hose. On the back of the intake my vac lines were all cracked up causing some issues
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post #3 of 7 Old 07-08-2020, 06:44 AM
Waterluvr
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When I get one in I suspect is plugged I look at live data on the scanner if it idles at all then take loose an O2 sensor to vent it, you'll know right away if it's plugged.
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post #4 of 7 Old 07-08-2020, 09:00 AM Thread Starter
Fab5father
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Thanks for the suggestions. The MAP sensor was replaced. Regarding vacuum leaks - if it were a vacuum leak, wouldn't the rough idle be consistent? But having said that I will take a close look at them and spray a little carb cleaner or WD40 on them to see if that makes any difference.

Regarding the O2 sensor - the Jeep will run fine for a while and then start to rough idle. If the O2 sensor was plugged wouldn't the rough idle be consistent?
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post #5 of 7 Old 07-08-2020, 12:01 PM
Waterluvr
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Quote:
Originally Posted by Fab5father View Post
Thanks for the suggestions. The MAP sensor was replaced. Regarding vacuum leaks - if it were a vacuum leak, wouldn't the rough idle be consistent? But having said that I will take a close look at them and spray a little carb cleaner or WD40 on them to see if that makes any difference.

Regarding the O2 sensor - the Jeep will run fine for a while and then start to rough idle. If the O2 sensor was plugged wouldn't the rough idle be consistent?
If a converter is plugged it won't "run fine" ever, transitioning from a cold start with it running ok to normal operating temperatures accompanied by problems indicates fuel management and related component failure.

Need to see some live data from cold start for fuel trims, temps etc. as it transitions from open to closed loop.
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post #6 of 7 Old 07-08-2020, 01:13 PM
jtec
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thoughts


Ideally - do you have a SCANNER - able to see live data?
Post ALL the codes you are seeing. Even if no scanner.

TRY the trick waterluver suggested - remove o2 sensor- easy cheap, remember to remove sensor BEFORE cat. a great DIYer test. just noisy.

your last post talks of o2 sensor being plugged - did you intend to say 'catalytic converter'
that is where this post started.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #7 of 7 Old 07-09-2020, 07:34 AM Thread Starter
Fab5father
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Yes, I meant catalytic converter. sorry 'bout that!

Yes I do have a scanner but it isn't super detailed like those shops have. Mine is a Millennium 90 Pro

The error codes I got initially are these three. After clearing the codes only the P0138 returned before I took it into the Jeep dealer to have them find the issue. I figured since they have a much better set of tools and are trained mechs they should be able to identify the issue. They've been looking since Monday and still have not figured out what's going on:

P0135 O2 Sensor Circuit Heater Circuit Bank 1 Sensor 1
P0138 Generic O2 Sensor Circuit High Voltage Bank 1 Sensor 2
P0141 O2 Sensor Circuit Heater Circuit Bank 1 Sensor 2
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