97grand4.0

So I replaced the rear O2 sensor, better, but no joy. Still 4 monitors not ready. I found a thing from NYS DMV for dealers that in a nutshell says the CTS has to stay above 190 deg. for closed loop for them to run, mine spends most of it's time around 183 to 187 ish, tho it does touch 190 occasionally. So I replaced the CTS, and got another 2 degrees out of it but still mostly below 190. Tomorrow I am replacing the thermostat with a 195 degree. This is the one AZ says is OE. Does anyone have experience with having to go even hotter?

Also, the NYS DMV thing says the 02 heater temps both have to be within 10 degrees of each other for the heater monitor to be ready. Ah, ha! Since I never have replaced the front sensor I plan on doing that too.

From what I gather, if the O2 heater monitor does not run, it will prevent a few others from running like CAT and O2 and EVAP monitors.

Here is the link, you have to kind of browse quickly and look at the red highlights in the picture of the failed emission inspection slip they have in each frame to see where they are going. They insist it has to stay above 190, or no love. I think I read Chrysler Jeep is 180 but not sure. Does anyone know for sure if closed loop is at 190, or is it 180?
http://www.nysada.com/portals/0/webi...nspections.pdf

97grand4.0

Im coming to the conclusion I have the wrong thermostat, they sell 180 and 195 for this application, I seem to recall thinking the 180 was a better choice. Not. This from the Stant thermostat site:
Thermostats have a “rated” temperature such as 180F or 195F
This is the temperature the thermostat will start to open, give or take 3 degrees
The thermostat fully open about 15-20 degrees above its rated temperature
(Mine is now operating from 183 - 189, should be above 195++ according to this, and well above..
Many thermostats have a “jiggle pin” or “check valve” that allows trapped air in the cooling system to pass through the thermostat and be released from the system.
If a Stant thermostat does not have a jiggle pin, it will have a "bleed notch” or other method of removing air from the system

dave1123

Stant thermos do not have a bypass hole in them, but the best way to remove all the air is to take out the temp sensor and fill it until coolant flows out the sensor hole, then put the sensor back in and continue filling. I'm using a Stant 195* stat now in my WJ and it runs around 195* to 210* all the time.

97grand4.0

Good info on your operating temps, confirms what I was thinking. My op temps are just too low for obd. I think the 180 barely worked for a while because it did pass last year, but they get a little out of spec and that would be enough to drop me too far.
I'll use your tip on filling through the cts. I recall having the burp problem as well.
The more i think the more it makes sense, obd2 requires 190F for emissions, per the DMV link above, you need heat to make the cat work, etc., and I am sure I have the 180 in there now. We shall see, not getting hopes up yet lol.

dave1123

Don't fill it thru the sensor hole! That's just insane! fill it thru the radiator using the sensor hole as an air vent. That way all the air in the block and head has someplace to exit. When you put the sensor back in, there's not a lot of air left in it. I don't think I put more than an additional quart in after that. Then maybe another quart as it warms up. Also make sure the thermostat heater hose goes to the lowest of the heater core pipes. The air in that will leave thru the water pump. Simple gravity physics.

97grand4.0

Yeah I wasn't going to fill it that way. OK, so........it appears I did have a duralast 195 in there, same as the one I just bought, and both have the little pin in there that constantly allows coolant to get by the Tstat. Ugh. Terrible design, ..I think this may be the reason I'm not getting up to temp? But am tempted to put it back together and see if maybe the new Tstat will work at higher temp then replace it again with a known name brand. %$@#$#%. lol.
Thanks for the tip on which heater hose to use.

dave1123

Wait!! A Stant Superstat is only $4! Why would you bother putting the old one back it?

CR-Snow

Couple of things to consider. When diagnosing these Kinds of issues, it's always best to go with OEM parts. Most folks recommend Mopar 195 stat. Also, the OEM supplied O2 sensors are NTK brand. Bosch makes a good O2, but for some reason, our computers tend to like the NTK ones the best. I went through a bunch of O2 problems figuring this out.

The upstream and downstream O2's should be replaced together. Downstream doesn't affect fuel trim, but The computer compares the two readings to determine catalytic efficiency.

If you need to get operating temps higher, you could take some cardboard and block the radiator off bit by bit until you reach operating temp.

Good luck man. Sounds like you've poured a ton of time in this mess. I feel your pain. Just as a last thought; my issue turned out to be a pinched signal wire from the 02 to the computer. It would intermittently cut out, resulting in a lean condition reading. Yours doesn't sound like it has this problem, but maybe you could check your harness for signs of wear.

97grand4.0

Yeah thanks for all that, I just hoofed it a half mile down and bought a stant SuperStat 195, ($9 vs $4); no weep hole in that one. It's also about 3 ounces heavier than the Dontalast. Another reason to replace both O2 sensors, according to the DMV in NYState, the heaters have to be within 10 degrees of each other, so I imagine the pcm compares resistance or current draw..right now I have one new and one old so that's my next project. But...dammit...I will see 195 on this thing today or my name's not 97grand lol.

97grand4.0

the plastic shroud is in the way, have to take out the radiator, meanwhile I couldnt get a good eyeball on it and overtightened the housing, cracked that. So I grabbed the tin snips and dispensed with the fan shroud, at least now I can work on it. Chrysler had their head up their *** when they designed that one.

CR-Snow

Exactly right on the O2 resistance. That's how it finds the efficiency.

I wish you could just register your jeep here in KY. We don't have emissions at all. Dang dang.

97grand4.0

What , no emissions in KY?? Dang dang is right. Taking a breather while my son picks me up a Dorman tstat housing. Dang cast aluminum. Its been an education since I got the scanner, tho, in a way it's nice to be able to figure it out and get it back to efficiency, so overall I'm not upset about it. But eh, that would change if I get pulled over. Sons here , so bbl

97grand4.0

All back together now and gained immediate +20F all the way around with the Stant stat. Anxious to see if the monitors liked it.

dave1123

About the cast aluminum t/stat housing. I've cracked a couple on Chevys and I've come to the conclusion that tightening one bolt a little too tight before tightening the other compresses the gasket on one side and adds a bending moment to the flanges. You have to make sure the gasket surface is perfectly clean of the old crap, then tighten the 2 bolts in stages, like torqueing a head. Yes, it's critical. Another thing, if the t/stat is mounted vertical, make sure it's located properly in it's groove and not slipped down.

You may still have a problem with the 02 resistance balance.

97grand4.0

Yea that was the problem the fan shroud on the 97 sticks over the housing and getting at the bottom bolt while keeping the tstat in place was a bear to say the very least. With it gone now lol it was easy to align the brand new shiny housing, and it took very little torque indeed to tighten it up. Sealed like new too, I think possibly the old one leaked despite best efforts. So you are familliar with the resistance balance concept on the O2's as well eh. Yea I will likely change it just for that reason, will pull a check wit the ohm meter just to see, and check the voltage.

Why they couldn't have done what chevy did and make the top half of the shroud unboltable, I do not know.