Overheat at Idle

[TheSloMoShow]

Ya, I used SeaFoam last night. The only place it was coming out was where you see in the video. But being it that's after the final O2 sensors, I'm doubtful it's the culprit. I'm going to have the exhaust shop seal it up this week, since they should fix their boo boo's.

If that don't fix it, then I'll replace the O2's.

And if that don't fix it, then, I'm out of options. I'll just have to live with it lol.

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[Ecomike]

Ok, so the 2001 used a California emissions design, but why in the hell would they stop using an O2 sensor after the final Cat(s-?) that were used to determine when the Cats failed? Is there one or two final cats on the 01 jeeps?

My sons 1996 Ford Taurus has 4 cats and 4-O2 sensors (I am sure of this, V-6 Vulcan 3.0), and I thought the first 2 sensors were after the first Cats, but now I am wondering if my memory is off there.

The earlier designs with pre cats, used the pre cats before the first O2 sensors as best I recall. I will check the 96 and 01 rigs (not jeeps) I have here.

 

[Ecomike]

Ya, I used SeaFoam last night. The only place it was coming out was where you see in the video. But being it that's after the final O2 sensors, I'm doubtful it's the culprit. I'm going to have the exhaust shop seal it up this week, since they should fix their boo boo's.

If that don't fix it, then I'll replace the O2's.

And if that don't fix it, then, I'm out of options. I'll just have to live with it lol.

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Hot air, and really hot exhaust air, like at idle, rises and that leak looks to be big enough and near enough to the block, oil pan and front of the transmission, so it very well could be the source of excess heat at idle!!!!!

You might try swapping the final O2 sensors for the initial O2 sensors, and see if anything changes just for fun? But get that leak fixed first.

Do you notice any power loss at full throttle, that could be a sign of clogging Cats?

Those mini cats are so close to the block/head that I just got to wondering if they may not be overheating (engine running rich instead of lean would make them very hot, well beyond design???) and passing that excess heat back to the engine enough to cause an issue?

My donut leak never showed up at idle in 3 muffler shop tests, only at >60 mph on a long 60 minute drive did it get serious and even then it did not show up except as low oil pressure and a heat spike right after I pulled off the freeway and reached a stop light, at idle.

Frankly I think the close proximity of the pre-cats to the engine was a bad idea to start with.

Did we ever find a source that says the LTFT is not ok at your -7 to -11 range? I have never really studied the LTFT and STFT topic yet.

I assume your seafoam smoke test confirmed no Ex-Manifold to engine head gasket leaks left after tightening the bolts?

 

[TheSloMoShow]

I thought that was weird too. So I have the 2 before and after the mini-cats (right off the exhaust manifold). I also have a main/big cat just before my muffler. It has an O2 bung, but no O2 for it. Weird.

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[Ecomike]

See post number 8 and number 13

http://www.jeepsunlimited.com/forums/showthread.php?450506-Removing-O2-Sensors-%282001-Cherokee%29&p=3967437&viewfull=1#post3967437

Claims there are 5, O2 sensors on 2001? Not sure if that is right as I would think yours would be throwing a code if one was missing at the end. And I recall reading before the 2001 had four O2 sensors here in several threads.

 

[Ecomike]

Just a thought, if the pre cats are going bad, loosing efficiency, then maybe the second batch of O2 sensors are not seeing enough change in the O2 concentration across the cats from the first 2 O2 sensors. Could the computer be compensating for that with LTFT????

 

[McQue]

cut and paste from a post I made on March 17 2008

Well, it turns out one of the differences of owning a 2001 XJ with Calif. Emissions is that your XJ has four 02 sensors. So, the bad news is you will eventually spend more money to replace 4 sensors instead of 2 sensors.
The good news is your scanner reports the Short Term Fuel Trim, and Long Term Fuel Trim, for each Bank of 3 injectors, as well as the O2 sensor data for each bank. If you have an injector performing marginally (rich or lean), just comparing the STFT and LTFT between the two banks will start to narrow down a problem.
Low trim percentages indicate that the PCM is not having to make large adjustments to the “preset tables” to get the A/F correct, so if both banks are reading low percentages, and those numbers are relatively close to each other, (within a couple of percent) then it can be a basic indication of balanced performance without having to go through the process of disconnecting each injector, one at a time, and then comparing the net change for STFT and LTFT that the PCM will create trying to makeup for a disconnected injector.
My initial scan today seems to show that the two banks are fairly well balanced.
Trim for both banks was around 2% at most in idle from start up open loop, through closed loop and on up to full running temperature.Once getting to closed loop, STFT and LTFT dropped to zero or went a little minus quite often, as the PCM seemed to be running the show greatly while things were warming up.
So, when I have more free time, I am going to measure and record STFT and LTFT at 1500 RPM and 2500 RPM and then do the injector by injector balance check so that I have a point of reference to work from in the future.

Thanks again for posting that article Mike.

 

[Ecomike]

Duplicate post, please delete

 

[Ecomike]

"Low trim percentages indicate that the PCM is not having to make large adjustments to the “preset tables” to get the A/F correct,"

So if he has larger injectors ( I think he does?) and the PCM compensates versus the preset table, the LTFT would be expected to park itself at a higher % number then?

I did not realize that fuel trim data was based on variations from data tables. I assumed that fuel trim data was based on O2 sensor data in closed loop. Just learned something more, thanks.

 

[TheSloMoShow]

You might try swapping the final O2 sensors for the initial O2 sensors, and see if anything changes just for fun? But get that leak fixed first.

Do you notice any power loss at full throttle, that could be a sign of clogging Cats?

Did we ever find a source that says the LTFT is not ok at your -7 to -11 range? I have never really studied the LTFT and STFT topic yet.

I assume your seafoam smoke test confirmed no Ex-Manifold to engine head gasket leaks left after tightening the bolts?

I'm definitely going to have the exhaust shop fix it up next Saturday. If that doesn't then I'll prob flip the pre for the post-cat O2's.

It's hard to say if I have any power loss because I don't have anything to reference it against. Although, I have always thought that Jeep is a bit slow accelerating while rolling at a decent speed. Usually rough once I peg the pedal to a certain spot it quickly picks up.

And yes, according to the "smoke test" there were no leaks by the manifold/head or manifold/gasket/mini-cat.

I do think that with higher flow injectors my LTFT should be negative. And maybe even slightly more negative than the more normal + or - 3% everyone seems to mention/is accustomed to.

But granted my overheat issue hasn't gotten any better, I believe the issue has to be in the exhaust or O2's....they're reading incorrectly regardless of injector spec.



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[TheSloMoShow]

"Low trim percentages indicate that the PCM is not having to make large adjustments to the “preset tables” to get the A/F correct,"

So if he has larger injectors ( I think he does?) and the PCM compensates versus the preset table, the LTFT would be expected to park itself at a higher % number then?

I did not realize that fuel trim data was based on variations from data tables. I assumed that fuel trim data was based on O2 sensor data in closed loop. Just learned something more, thanks.

I wonder if anyone had any technical experience in this matter. After installing the Bosch 280155784's, my LTFT I'd about -7 or 8% for both banks. At 49psi the injectors flow rate is ~ 24.9lbs/hr, so 10% more than stock injector spec. I wonder if this LTFT would be assumed to be normal?

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[TheSloMoShow]

Actually, everything I'm seeing now rates these 784's at 21.3lbs at 3bar. So that's almost spot on to stock spec when at 01 XJ rail fuel pressure......hmmm......

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[Ecomike]

You might post that question up the modified forum.

 

[TheSloMoShow]

So I had the exhaust shop weld up both of the seams on the exhaust to fully seal it off. No change though to my O2 sensor readings, or the coolant temps.

I'm beginning to wonder if my current condition really presents any danger or risk. As long as I'm moving, temps are no higher than 210. It's only when I come to a dead stop that the temp will rise, eventually turning on the efan after 5 or so minutes to keep the temps from reaching the gauge line after the 210 mark. They never creep past 223/225 at idle, and once efan comes on it'll go back down to 215/216 before creeping up in a few minutes again. Except for once when I was in bumper to bumper traffic for well over an hour, and even with efan on the temps rose to 237 but this was just one time. This is all in 80-95 degree weather in Columbus OH this summer.

Next, I think I'll swap pre for post O2 sensors, and/or may just replace all 4 to see if any effect on LTFT's and coolant temps.

Pending some feedback from the modified section on the injector swap, I may have to call it a day after installing new O2's. I'd be at a complete loss from there if Jeep is still behaving in the same manner.

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[Ecomike]

My daughter's 2001 Saturn, and my son's 1996 Ford Taurus both run at 220-222 F with the AC off, and a little cooler with the AC on as the Efan runs all the time on high speed with the AC on. That is considered normal for both. My son's cycles the E-fan at about 223 on and about 212 off. And it cycles a lot. The Saturn seems to stay stable at 220 F (may be lower, like 212-215, not sure what the actual temp is) all the time as I recall once it reaches peak temps.

"As long as I'm moving, temps are no higher than 210. It's only when I come to a dead stop that the temp will rise, eventually turning on the efan after 5 or so minutes to keep the temps from reaching the gauge line after the 210 mark. They never creep past 223/225 at idle, and once efan comes on it'll go back down to 215/216 before creeping up in a few minutes again"

So that all sounds perfectly normal. The concern is that one day you say it spiked in heavy traffic on a long time drive.

"once when I was in bumper to bumper traffic for well over an hour, and even with efan on the temps rose to 237 but this was just one time."

I test mine with the parking brake on, in drive at idle for an hour with and with out the AC on to simulate parking lot freeways for an hour to see worst case situations. I have no hills or mountains to worry about on mine and no trailers.

 

[TheSloMoShow]

So that all sounds perfectly normal. The concern is that one day you say it spiked in heavy traffic on a long time drive.

Yep, this was really my only concern too. If the e-fan kept it from creeping past 223/225 ALL the time, then I'd be OK. But the fact that it was able to happen once concerns me. It's only going to take one time to blow that head gasket, and I surely don't want to mess around with having to replace that.

I'm sure my employer will enjoy me coming in super early and leaving super late now to avoid the traffic

 

[techno1154]

Yep, this was really my only concern too. If the e-fan kept it from creeping past 223/225 ALL the time, then I'd be OK. But the fact that it was able to happen once concerns me. It's only going to take one time to blow that head gasket, and I surely don't want to mess around with having to replace that.

(QUOTE )]

You may be on to something if you could determine what the problem is. My XJ used to do that, heating up to 225 degrees or a bit higher occasionally in stop and go traffic or going through a drive through. The electric fan always brought it back down. Remembering my 1994 XJ did not have an electric fan I set about replacing every single item in the cooling system except the fan blade. Nothing helped. Then I replaced both fans with an after market dual electric fan kit and thermostat switch. I am still happy with the results 10 years later.

My move was a bit radical. I will not advice anyone to do the same.

 

[TheSloMoShow]

You may be on to something if you could determine what the problem is. My XJ used to do that, heating up to 225 degrees or a bit higher occasionally in stop and go traffic or going through a drive through. The electric fan always brought it back down. Remembering my 1994 XJ did not have an electric fan I set about replacing every single item in the cooling system except the fan blade. Nothing helped. Then I replaced both fans with an after market dual electric fan kit and thermostat switch. I am still happy with the results 10 years later.

My move was a bit radical. I will not advice anyone to do the same.

I'm curious, why wouldn't you advise anyone to do the same?

I've actually installed 2 new e-fans (17in) on the front of my condenser, and they run off an ignition power source, so at all times. Really the only difference between mine and yours is the electric fan on the inside of the bay (mine is set to a delay timer for after shutdown, but I could always add in a toggle switch to have it run continuously in the summer) and thermostat switch.

What does your tstat switch do, turn on the e-fan at a different temp?

I have always wondered why my efan doesn't trigger to come on until ~ 221*F unless that's just normal operating condition.

 

[techno1154]

Why I would not advice it? Back when I did it it was pure blaspheme to remove the mechanical fan or use synthetic ATF in the AW4. I did both at 135,000 miles. The XJ now shows 285,000 + miles and exhibits no ill effects.

Looking back, I am convinced that the mechanical fan move more air than any electric fan that will fit the XJ radiator. Why the fan on my XJ did not work properly is anyone guess.

Yes, I have thermostat switch to turn on the fans at a set temperature (about 215 degrees on the guage) and does so without my input.

 

[TheSloMoShow]

So I switched out the O2's tonight (as well as a passenger door lock actuator ).

Here's two quick pictures of what I pulled out.

B1S1, B1S2, B2S1, B2S2 from left to right.

I don't notice anything abnormal. Do you?

This is the last thing I could think of to try and solve my "overheating" problems. If the condition maintains its current condition, them I'm stumped and have firm belief this is just the way it runs lol.



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