A stuck-shut thermostat would make the truck run hotter ...

RwP

 

Unless there's a change in programming in the last 15 years or so, the computer uses one of the two sensors to read engine temperature. The other one is what the gauge uses. You definitely want the 195 unit. Sometimes the jggle valve is hard to see. If there isn't one, I drill a 1/64 hole. This has done me well for the last 50 years. My last repair on one was last week.

 

Ya think Ralph As I laugh at myself.
Thanks Ol grouch I thought that might be possible, good to know that size I might have gone too big. . There is definitely no jiggle in the ones I saw. the Duralast one is on the inner area on the part of the valve that goes up and down.

 

Lots of internet folklore in here.......

First, Run a few more tanks through it and see if it has really dropped in mpg.
Assuming it has, I would go back and read post 2 again.... check tires, etc.
Check the new spark plug wires and make sure one is not rubbing or burned....
Pull the sparkplugs and see if they all look the same.... ie: burning pattern
You have a 180 t-stat. How long ago did you put that in? Unless the drop in mpg and the t-stat replacement were the same.... it has nothng to do with it.
Do you have a scanner, or access to a scanner? If so, take some readings, ie: how quickly are you going to closed loop? Is it staying there, other then hard acceleration, etc? is the computer seeing a coolant temp. that is accurate?
What brand O2 sensor did you use? Some of the aftermarket ones dont last and are slow to respond.

Personally, I cannot find anywhere where Chrysler states what temp. the coolant needs to be for closed loop to happen.
I have read on the internet 125F I can tell you on early to mid 90's GM it was 142F.
In no way, would the 180F tstat cause the engine not to go into closed loop yet a 195 is fine.

FWIW. I suspect what cc.5 said, in post 9, to have a lot of truth in it. Chrysler is allowing closed loop as soon as the O2 sensor is operational, and not so much based on coolant temp, which is why they dont seem to show coolant temp required tor closed loop in the service manual.
And if you dont have the service manual, the 95 is on this forum. I think, for the most part, the fuel injection-ignition, is pretty much the same for 92-95.
Good luck and let us know what you find.

 

Now I get to expose more ignorance. I don't know what closed loop means. I had assumed it meant correct operating temp. I just looked into the cooling system chap for the 95 FSM. It didn't say anything about closed loop and I did not run across specified temp. after looking at the picture with the very oddly shaped T I'm asking myself does mine go in spring down or up?

Found this https://dodgeforum.com/how-tos/a/dod...rmostat-394090
It is spring side down. And teh O2 sensor is form RA I think it is Walker? Does that sound right? They were on sale and someone on here posted about changing theirs. How frequently do they need changed?

 

"Open Loop" and "Closed Loop" refers to feed back systems; specifically, on a car, on if the ECU is using prewritten tables or is actually monitoring engine condition (like the O2s etc.) to determine the air/fuel/spark settings.

I don't know about a Walker O2; I'd stick with Mopar and (for Mopars) NTK/NTG O2s. I learned the hard way, don't use a Bosch when a NTK is OEM. They don't have the same curve and can totally screw up the ECU's response to air/fuel events. At least on Fords.

(OTOH, my 2000 Malibu loved a Bosch sensor, since that's who made them for GM. Weird, that.)

EDIT: Sorry. It's been recommended by some of the professional tuners to replace your upstream O2s every 60,000 to 80,000 miles. For my 1988, it's recommended in the FSM to replace every 105,000 miles or 168,000 KMs. For a 1993, they don't list an inspection/replacement period. I'd stick with 100,000 miles or so as a coarse rule of thumb.

RwP

 

Oh, and open/closed loop is discussed in quite some detail in the factory service manual and in almost any "How To Tune Your EFI System" book - if you go to the books, I'd recommend Greg Banish's books first. (Also LaSota's if you have a Ford, but since these aren't Fords, his particulars don't apply ... )

RwP

 

I took a break after finding out I didn't remember what I thought I did
I have only torn into this thing one time to do the plenum WP TC and sensors and small parts under there with an instruction page from Hughes.Turns out IDK how to get that Tstat housing out. It has lips that catch. I looked and it seems like removing the two generator mounting bolts should do it. I'll be bach
Oh yea all the tires were embarrassingly low. less than 30 on all 4. I pumped em up to 37/38psi BFG All Terrain

Thank you again Ralph. This it in the 95 FSM ch14p28 tells me all I will need for now The index is my friend now
During Open Loop modes, the powertrain control
module (PCM) receives input signals and responds
only according to preset internal programming. Input
from the oxygen (O2S) sensor is not monitored during
Open Loop modes.
During Closed Loop modes, the powertrain control
module (PCM) will monitor the oxygen (O2S) sensor
input. This input indicates to the PCM whether or
not the calculated injector pulse width results in the
ideal air-fuel ratio. This ratio is 14.7 parts air to 1
part fuel. By monitoring the exhaust oxygen content
through the O2S sensor, the PCM can fine tune theinjector pulse width. This is done to achieve optimum
fuel economy combined with low emission engine performance.

The single-port fuel injection system has the following
modes of operation:
² Ignition switch On
² Engine start-up
² Engine warm-up
² Cruise (Idle)
² Acceleration
² Deceleration
² Wide Open Throttle
² Ignition switch OFF
The ignition switch On, engine start-up (crank), engine
warm-up, and wide open throttle modes are
Open Loop modes. The acceleration, deceleration and
cruise modes (with the engine at operating temperature),
are Closed Loop modes

93Ragtop- Thanks I have the snap on MT 2500 from ebay. I have to use the manual when I hook it u p. I'll look into that. I have only used it to set fuel sync and because I accidentally discovered it reset the IAC. On every other attempt to use it I was not able to get it to do what the manual said it should. ??

 

She's in. had to add more coolant than I expected. It seemed tighter but that usually happens when I disconnect the battery for a while. Temp was just past half way. after driving in the hills and through the rural parts for 15 miles. I'll post next time I fill up to see what result I have.
Only had to loosen the bottom bolt and take out the top bolt of the generator to get the T hose & housing out.

 

Checked the plugs just now. Started with 5 just a bit of grey, brushed it. Then #3 smelled heavily of gas once I removed it. #1 was the same. 2, 4, 6 smelled of gas when I put them closer to my face. I had started it for 30 seconds just previous to this. Otherwise the plugs were all the same. They are Champion Iridium. The wires did go down on several of them when I pushed them on top of the dist cap. I have had the 180 for years and its always been 15+ down to 13+mpg. I had never even come close to running out at less than 300 miles on a tank since I did the plenum. Could be the gas I used and teh low air pressure in the tires had to have had some part in it.
Edit- Went through the functional tests the MT2500 has in it and there were no codes and everything else was normal.