Cold Air Intake Problem

MARC CROMER

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Joined
May 18, 2018
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25
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San Diego
Hi all, I have been chasing a possible CAI problem for 2 years and about $1K invested. I am original owner for 2000 TJ (federal vehicle from Colorado). Short story is factory catalytic converter started to rattle at 50K miles. Yes, only 50K on my "baby".

I live in CA now and there are no factory cat available these days, so performance muffler shop installs a generic Catco brand. Well, I have gone through 3 more cats in the past 15K miles and many mechanics + dynomometers all say everything is working fine (no leaks, no lights, trimming out fine) and they don't understand.

Yesterday, took to Jeep dealer. They monitored the O2 sensors and showed me lagging response to changes in airflow.

They claim that my Rock-It brand CAI allows too much airflow for 2000-era software and O2 programs to compensate. This sends too much gas to carburetor and creates a HOT catalytic converter and too hot for aftermarket cat. They say the factory CAI is balanced for the software and exhaust system.

These are seasoned Jeep mechanics with Chrysler diagnostics (not the SnapOn stuff).

1.) What do you think?? I am going to put my factory CAI back on.
 
Well, I can't say for sure that the cold air intake is your issue, but it has been proven that the filters that many of these air intakes use (i.e. K&N for instance) let more particles and debris into your engine.

The bottom line is that a cold air intake for a TJ is a gigantic waste of money. You won't gain anything from it and you'll wish bringing more contaminants into your engine.

I'd trust the Chrysler mechanics though. If they're telling you to put back on the stock intake, I would heed their advice.
 
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...

They claim that my Rock-It brand CAI allows too much airflow for 2000-era software and O2 programs to compensate. This sends too much gas to carburetor and creates a HOT catalytic converter and too hot for aftermarket cat. They say the factory CAI is balanced for the software and exhaust system...

My understanding is that the factory intake is not the restriction in the engine. If true, how does an aftermarket intake allow the engine pull more air than it could before?

I hope your mechanic doesn't think your TJ has a carb. ;)
 
I seriously doubt your cold air intake is causing your problem. That being said, there is nothing wrong with the stock air filter system. I have a cold air intake for the sole purpose of clearance for my Kilby on board air compressor.
 
My understanding is that the factory intake is not the restriction in the engine. If true, how does an aftermarket intake allow the engine pull more air than it could before?

I hope your mechanic doesn't think your TJ has a carb. ;)

Yeah. this....If that Carburetor reference was not a typo from you...its time to find a new shop. Those guys don't know what they are talking about. A TJ does not have a carburetor. It has a throttle body with multiple fuel injectors. Plus, its well documented that the Factory induction system does NOT restrict airflow to the engine...so its not possible that your CAI would INCREASE airflow. The engine wasn't restricted anyway, so a CAI or Factory system will flow enough air for the motor.

Its kind of like how a lamp doesn't get brighter if you install a heavier duty extension cord. The original cord wasn't restricting the amount of electricity flowing to the lamp, so putting a less restrictive one on doesn't make any difference.
 
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Knowing what little I know about this, my instinct is that this is an O2 sensor problem or some other fuel management sensor.
 
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Hi all, I have been chasing a possible CAI problem for 2 years and about $1K invested. I am original owner for 2000 TJ (federal vehicle from Colorado). Short story is factory catalytic converter started to rattle at 50K miles. Yes, only 50K on my "baby".

I live in CA now and there are no factory cat available these days, so performance muffler shop installs a generic Catco brand. Well, I have gone through 3 more cats in the past 15K miles and many mechanics + dynomometers all say everything is working fine (no leaks, no lights, trimming out fine) and they don't understand.

Yesterday, took to Jeep dealer. They monitored the O2 sensors and showed me lagging response to changes in airflow.

They claim that my Rock-It brand CAI allows too much airflow for 2000-era software and O2 programs to compensate. This sends too much gas to carburetor and creates a HOT catalytic converter and too hot for aftermarket cat. They say the factory CAI is balanced for the software and exhaust system.

These are seasoned Jeep mechanics with Chrysler diagnostics (not the SnapOn stuff).

1.) What do you think?? I am going to put my factory CAI back on.
Marc you got a bigger problem. Our TJs do not have carburators.
I hope that is a typo... are you sure it says Chrysler in their building?
 
Thanks everyone. My bad on the use of “carburetor” instead of “throttle body”. You all seemed to get the idea, though. If factory intake is proven not to restrict, i will get new o2 sensors. Also, will discuss with Chrystler more next week. YES, i have had 3 cats from Catco turned to rattle cans in 15K miles. No melting has been observed, just breaking up.
 
They claim that my Rock-It brand CAI allows too much airflow for 2000-era software and O2 programs to compensate. This sends too much gas to carburetor and creates a HOT catalytic converter and too hot for aftermarket cat. They say the factory CAI is balanced for the software and exhaust system.
I'm not fan of CAI's but that's complete bullshit. The airflow is only what the engine is pulling and the OE air intake allows just as much air as that Rock-It CAI is allowing. That CAI is not somehow magically forcing more air to flow than the OE air intake easily flows. Jim Repp, the "father" of the Jeep Rubicon, was Jeep's senior-most engineer and he carefully explained that they designed the OE air intake system to be absolutely 100% non-restrictive and flow more air than the engine could possible consume/ask for. It will easily flow far more air than the engine can pull at redline rpms and wide-open throttle so that Rock-It CAI is not flowing any more air whatsoever. I'll say it again... that claim was pure ignorant bullshit.
 
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Re-reading this, I wonder if this shop "full of seasoned Jeep mechanics" is trying to deflect blame away the crap cats they are installing.
 
I'm not fan of CAI's but that's complete bullshit. The airflow is only what the engine is pulling and the OE air intake allows just as much air as that Rock-It CAI is allowing. That CAI is not somehow magically forcing more air to flow than the OE air intake easily flows. Jim Repp, the "father" of the Jeep Rubicon, was Jeep's senior-most engineer and he carefully explained that they designed the OE air intake system to be absolutely 100% non-restrictive and flow more air than the engine could possible consume/ask for. It will easily flow far more air than the engine can pull at redline rpms and wide-open throttle so that Rock-It CAI is not flowing any more air whatsoever. I'll say it again... that claim was pure ignorant bullshit.
Did the engineer write this somewhere or say it on film? Or is it just hear say? I agree with you. Just curious if we have anything that we could use to put in the FAQ for future reference.
 
Did the engineer write this somewhere or say it on film? Or is it just hear say? I agree with you. Just curious if we have anything that we could use to put in the FAQ for future reference.
It was strictly verbal over multiple conversations I had with Jim Repp. Our conversations started after I started making posts looking for help on multiple misfires causing multiple '43' codes on my '97 TJ. His engineering team was looking for a test mule to try some fixes on it and he found my posts so after we spoke, he sent me all kinds of parts to try. Nothing helped, the problem was eventually tracked down to bad valve springs the factory had received. We ended up talking a lot over the next couple years and during one of those, I asked him about the OE air intake and he filled me in on what I related above. He was also feeding me advance info on the Rubicon to "leak" like to quell some of the bad pre-release rumors on the Japanese lockers that were going to be included. He told me all about how his dream was a Jeep with lockers 4:1, etc. with 33" tires. The 33" tires never made it but everything else did. He was a through-and-through Jeeper/wheeler. At the time we spoke he was their senior-most Jeep engineer.

 
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