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Down to the MAF Sensor or Cat Converter.

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The Dajaaza
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Joined: 14 Dec 2005
Location: St. John's Newfoundland

PostPosted: Tue Jan 10, 2006 8:04 am    Post subject: Down to the MAF Sensor or Cat Converter. Reply with quote

97 TJ, 2.5litre

Just before Christmas, just before a trip to the great white north, I was having trouble with a front O2 sensor error code. By the advice of my shop as well as a couple of replies made to me here, I ignored the code and headed out on my trip (December 23).

There is a usual gas stop that is made about 3 hours into this trip at a town about half way across the island. In my old 90' 2.2litre Celica, I'd stop here and spend just over $30 Canadian gassing up. Knowing that Jeeps are a little harder on gas, I figured that I'd be spending about $40-45 on fuel, but instead, the tank took $69! I was blown away. With a tight schedule, having to deal with ferry rides and the sort, I didnt have time to pull into a shop to buy a new O2 sensor so we just kept truckin.

The next night, and over $300 in fuel later, we finally arrived at our destination and there was a call waiting for me from my father. (we stopped at his place halfway through the journey). He said that when we left his house that morning there was mountain of soot left in the driveway and the Jeep was pure flooding fuel!

So we extended our visit a day and I got the Jeep into a shop (December 27) to replace the O2 sensor as well as the air filter.

By no question, that did the trick! The Jeep ran great and we only burned about half the money in fuel coming back.

Last thursday (January 5), after driving about an hour, I began to notice some hesitation in the vehicle and in no time the engine light came back on. She had a hard time maintaining speed but if I put the pedal to the floor, she would kick in and climb again. So I ventured back to the shop and was told of a reading of the rear sensor acting up. I replaced that sensor yesterday and still have the symptom of hesitation after the Jeep reaches normal operating temperature.

So I've since been searching for an answer, through various resources on the net, and it seems to come down to the MAF sensor, or the Cat converter. I just have a couple of questions about these two.

If it were the cat converter causing the trouble, would I only get hesitation after normal operating temp or would I see this right away at cold start up.

And if it were the maf sensor, what chances are there of the check engine light coming back on to indicate this. Are these typical symptoms of a maf sensor?

I'm not very familiar with the characteristics of either of these so any insight would be great,
J
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Lowrider
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Joined: 08 Nov 2005
Location: Washington State

PostPosted: Tue Jan 10, 2006 11:15 am    Post subject: Reply with quote

Could also be the EGR valve. I had one going out on my company rig, a Chev S-10, and the symptoms were exactly as you describe.
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She was only a fisherman's daughter,
But when she saw my rod she reeled.


2006 Wrangler Unlimited
1997 Cherokee Sport 2WD
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KnightFire
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Joined: 07 Jan 2004
Location: Hanover, MD

PostPosted: Tue Jan 10, 2006 12:12 pm    Post subject: Reply with quote

I thought all Jeeps were speed density?! No MAF. Someone correct me here if I'm wrong.

Quick way to tell if your cat is going bad...get up to operating temp, crawl under and see if the exhaust manifold/header is glowing Smile
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2002 TJ Wrangler X
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The Dajaaza
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Joined: 14 Dec 2005
Location: St. John's Newfoundland

PostPosted: Tue Jan 10, 2006 3:00 pm    Post subject: Reply with quote

The latest news.

Tonight, the engine light came on and read "code 51".
Code 51 indicates a lean air/fuel mixture by an abnormally rich correction factor.

To Lowrider:
Thanks for the reply. What exactly is the purpose of an EGR valve and is it repairable or does it simply need to be replaced?
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Lowrider
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Joined: 08 Nov 2005
Location: Washington State

PostPosted: Tue Jan 10, 2006 3:16 pm    Post subject: Reply with quote

They're a throw-away item. About $150.

They are a variable valve that mixes exhaust gas into your engine's intake for the purpose of re-burning unburned hydrocarbons. The valve opening varies depending on engine temperature, engine load, and other factors. If the valve goes bad it'll open too much and feed too much exhaust into the intake or it'll act like the mother of all vacuum leaks. Won't run worth a damn at low throttle settings, won't idle, and the only time it'll run much good at all is with the throttle to the floor.
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She was only a fisherman's daughter,
But when she saw my rod she reeled.


2006 Wrangler Unlimited
1997 Cherokee Sport 2WD
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KnightFire
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Joined: 07 Jan 2004
Location: Hanover, MD

PostPosted: Tue Jan 10, 2006 3:18 pm    Post subject: Reply with quote

EGR-Exhaust Gas Recirculation, pretty much does just what it says (It's for emissions) and plays a part as a knock module. It can be cleaned, but their not very expensive, just replace it.
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bltracer
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Joined: 04 Apr 2005
Location: Pollock Pines, CA

PostPosted: Wed Jan 11, 2006 5:35 pm    Post subject: Reply with quote

Did you use genuine mopar O2 sensors or after market???

I had a similar prob with my 97, front O2 went out, ran rich, put in an aftermarket one. Not long after, ran rich again. I ran it this way until the cat took out the rear O2 then finally plugged up the muffler. $1500 later (Header, Front O2, Cat, Rear O2, Muffler, Plus Install) I learned my lesson... Get Genuine O2's from a dealer and have the Cat checked/replaced soon. I work for an auto parts house and sell Bosch O2 sensors daily, but after what I went through, I would only reccommend Mopar ones for a TJ.

My 2 cents


bltracer
97 TJ SE
2.5L 5speed
3 1/2" RE Lift
3" Body Lift
Pacesetter Header
K&N Air Filter
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The Dajaaza
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Joined: 14 Dec 2005
Location: St. John's Newfoundland

PostPosted: Wed Jan 11, 2006 7:24 pm    Post subject: Reply with quote

The front sensor was Bosch and the rear was a "fits-all" unknown.
The difference here is that when the sensors went, the codes indicated it was the sensors. Now however, the code is reading a lean mixture, not rich. I'm gonna get the cat checked out soon and see where that takes me.

Question..
If the cat were bad (clogged), would the Jeep run lean or rich?
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bltracer
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Joined: 04 Apr 2005
Location: Pollock Pines, CA

PostPosted: Fri Jan 13, 2006 1:10 pm    Post subject: Reply with quote

If your Cat is not working, the rear O2 sensor will not pick up any difference from the front O2 and should give an appropriate code. You might get a good OBD II scanner and read what the O2's are doing...


bltracer
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KnightFire
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Joined: 07 Jan 2004
Location: Hanover, MD

PostPosted: Fri Jan 13, 2006 10:41 pm    Post subject: Reply with quote

The Dajaaza wrote:

Question..
If the cat were bad (clogged), would the Jeep run lean or rich?


It really depends on what the rear O2 sensor is telling the PCM (it would most likely be lean though), however if the Cat is clogged, you can be assured that it's getting bad readings.
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Scuba Wino
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Joined: 31 Jan 2006
Location: Sacramento, CA

PostPosted: Wed Feb 01, 2006 8:34 am    Post subject: Reply with quote

Just my .02, but

My '98 has had only 3 problems since I bought it new in '97.

1 radiator: The plastic top half started leaking and blowing fluid all over my belts

2..YES 2 f'ing valve jobs....why you ask?
After the second valvle job (31,000 miles after the first valvle job) I had to take the jeep back to the shop because the check engine light came back on (YES, 11 miles after my SECOND valve job..). Turns out:

The throttle body switch used in that year Jeep was made with no "O" ring to keep out moisture. When my radiator blew, water got in the switch and months later fried my valvles. The f'ing Jeep dealer (no names, but it's the only one in Woodland, CA) didn't catch the switch and just fixed the probelm (vavle job).

Well, turns out, that if this switch is bad...all kinds of havoc are reaped on your machine. Have it checked, it's an easy and quick $90.00 fix tht will save you gas milage and future valvle jobs.

Just my .02...thanks for listening.

SW
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The Dajaaza
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Joined: 14 Dec 2005
Location: St. John's Newfoundland

PostPosted: Wed Feb 01, 2006 8:58 am    Post subject: Reply with quote

It was in fact the result of the replaced front sensor failing a second time.

Why you ask?
The power steering switch was bad and leaking and was sitting on the same ground as the O2 sensor. The bad ground caused the second sensor to blow. So the switch was disabled, the O2 replaced yet again, and she ran fine. So far I don't see the need of the power steering switch. The purpose of the switch was explained to me: to increase throttle when steering so the vehicle doesnt stall upon receiving pressure from power steering. But before and after the switch had been disabled, I didnt see much change in throttle level, and she hasnt yet stalled.

Since then... about ten days later, the Jeep was getting irratic idling and eventually, that damn light came on again reading code 24 (Throttle Position Sensor). On back to the shop I went where they chose not to replace the sensor, but instead iliminate all the corrosion for the grounds to the engine, body, battery, and the main harness to the fuse block.

It took about a day and a half, but everything settled back down and she's running fine.

Talk about gremlins!

One thing I did wonder though, and I was actually gonna start a new thread on this....

...The day before the irratic idling, I poured a bottle of injector cleaner and a full tank of gas into the vehicle. The cleaner was a "Lucas" product which usually has a reputation as being a gutsy, potent, and heavily concentrated fluid whether it be injector cleaner, power steering stop leak, stabilizer, etc.

The question: Is it possible that the odd mixture of fuel with the heavy duty injector cleaner would cause the idling to jump around?

Jeremy
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scottheath5499
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Joined: 24 Mar 2006

PostPosted: Fri Mar 24, 2006 6:28 am    Post subject: Reply with quote

I could have written the original thread myself. I bought a 97 TJ about 3 weeks ago. I am having the EXACT same problem you are. At the time of purchase the used car dealer had already replaced the upstream O2 sensor. The Jeep ran fine for a few days. I also ran a can of Gumout fuel injector cleaner through it. After about a half a tank of gas, engine light, code 51. I replaced both O2 sensors with Bosch aftermarket. Ran fine for 9 days. Then, engine light, code 51. Took it to the local dealer. They replaced plugs, plug wires, distributor cap, rotor button, cleaned injectors, cleaned valves, updated PCM based on a bulletin. Fifteen miles later, engine light, code 51. Went right back to the dealer that day! Hooked it back up, both O2 sensors bad. They recommended Mopar O2 sensors but they had to order them. I had them to order a converter also and both will be installed Monday. I found a post somewhere on the internet that said the 97 TJ doesn't have an EGR valve. Not sure myself, I found a picture of one and searched all over my Jeep for it but couldn't find it. Sorry if I haven't been any help to you so far but if and when I do get mine fixed I'll let you know what it was. I would appreciate it if you would do the same. My email is rsheath@usit.net.
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soulknight
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Joined: 01 Apr 2006

PostPosted: Sat Apr 08, 2006 5:02 am    Post subject: Reply with quote

I too have been having the exact same problems. Replaced O2 sensors multiple times, the cat and coolant temp sensor. Computer says I am still running lean and I am afraid these problems might toast my new cat. Dealers around here hear have been no help at all. I feel like I am chasing a ghost inside my engine. Please email me also if anyone has found a definate fix for this problem. myrthmaker@yahoo.com

Eratic idling can be cause Idle Air Control sensor. It is a sensor and small motor on the side of you throttle body that adjusts intake while the Jeep is idling and really only idling.
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Titan4u2c
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Joined: 03 Dec 2005
Location: Clayton, NC

PostPosted: Sun Apr 09, 2006 2:09 pm    Post subject: Reply with quote

Does anyone know where this EGR valve is on a '91 XJ, sounds like I may have found my problem. Also is it a MAF or...MAP sensor on these things and anyone know how much they run pricewize? Also do they make a difference on if the model is an auto or manual? Any help appreciated guys, ty.
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