Topic: Running Rich - Low Engine Temp

[jrager]

Rig

1993 YJ 2.5L
Pacesetter headers / Custom Highflow Exhaust cat eliminated
19lb HR TypeIII Injectors
62mm Bored 4.0 Throtle body ported intake to match
Cold air intake
MSD Performance wires
Champion Copper Plus gapped .55
195Deg Thermostat ( just replaced)
All new sensors O2,CPS,IAC,MAP,Coolant sensor, Temp Sender, pretty much every other sensor on the motor replaced in the last 12 months.


Ok now the issues Have two:

1 . It has been Running rich for a while but with the cat eliminated has gotten way worse. I have changed out and checked about everything 10 times. The only thing that is interesting is my motor will not get hot. it stays at 170-190 degrees and i have made sure I have correct 195 Deg thermostat. Even heavy wheeling this thing does not get hot. Which goes against what pretty much everyone says should be happening typically opposite. I am not sure if there is a correlation. But I just cant figure out what is causing it to run rich or why so cold natured. What are the conditions in the ECU that drives a rich state. Maybe I can approach this from a different approach. Or any thoughts or help would be appreciated.


2. Performance Ignition -  On thing I tried to solve the rich state was well if it is going to run rich might as well use that fuel to create some ponies. However I have tried both a PD Screamin Demon, and an MSD performaced Dist. Runs strong for less than a minute then the ECU freaks out eventually the vehicle quits running. I am pretty sure the spark is jumping in the Distributor. I know a lot of people run these with no issues not sure what I am missing. I built a custom set of wires so I know that is not the issue drop the stock ignition back in and runs perfect except still runnin rich...

Thanks for any help!

[Jeffy]

I'm going to guess the reason your engine is running rich is because it's in open-loop.  This is because it's running too cool and the ECM isn't going into closed loop which it should be doing once it gets to operating temp.  170 is really low and so is 190.  It should be getting to at least 200*.  Is your thermostat opening at all?  At those temps it shouldn't be which should cause the engine to heat up.  With the cap off, the coolant level should start to rise then maybe spill a little. Once the engine hits the T-Stat temp you should see the radiator level drop then start flowing.

What might be happening is the thermostat might be always open which never lets the engine heat up.

[bootguy]

I live in the Pacific Northwest and had to go to the 160/165 deg. thermostat as I would not get up to temperature either.  What part of the country are you in?

[jrager]

Amboy Wa

I am leaning towards the engine temp being the issue as well but I do not have a solution. I have swapped the thermostat and changed the sensors. Maybe I could go up to a 205 degree T stat and do a complete system flush.

Seems odd that it does not get hot.

[Jeffy]

Amboy Wa

I am leaning towards the engine temp being the issue as well but I do not have a solution. I have swapped the thermostat and changed the sensors. Maybe I could go up to a 205 degree T stat and do a complete system flush.

Seems odd that it does not get hot.

Well, I'd make sure the thermostat is actually working.  The thermostat needs to stay closed for the engine to heat up and should only be opening once it's to temp.  You should be able to see it flowing if you leave the radiator cap off.

[jrager]

This is where it sits it will fluctuate a little both ways but stays right about here.

[Jeffy]

IIRC, that's about where it should be for 195*.

[jrager]

I cant figure out any other reason why it would be staying in open loop and running super rich? I replaced the O2 again last night.

I found a 205 deg T-stat so gonna try that and flush then report back.

Maybe a re-manufactured ecu maybe buy a reader to help troubleshoot

[Jeffy]

I wonder if the temp sender for the ECU is working.  I don't think a 205 stat will help.

[bootguy]

that is where mine sits also.  I would look other places.

[jrager]

Issue resolved

I bought a Bosch 1300 so I could monitor all the engine functions and sensors.

I determined something was causing the ECU to go back and forth between lean and rich but really squirting a lot in almost like over compensating

So here are the 2 things I did and tested and now all the systems are working properly.

Mod 1  - I fabed up a new exhaust adding a high flow cat back in and tail pipe with rear exit. The O2 sensor seemed to not like no back pressure with just a muffler and dump. I don't know if this really solved my rich condition but it runs way better and lower end torque is back.

Mod 2 - I put in a Fuel pressure regulator from a 1993 Dodge caravan. So here is where I believe the real issue was I have the ford mustang typeIII injectors and they are rated at a higher PSI and what I think was happening is the computer couldn't figure out how much fuel to squirt or how long of a duration. So it was consrtantly adding too much fuel when I added a ton more air flow with the 62mm TB it compounded the problem and the computer could not solve and just keeps cycling trying to adjust. I added a 44-50 PSI regulator and seem sot have solved. As a side bonus all the mods seem to be working together and noticeable power improvement and holy throttle response!

[95 Lowbuck]

Just my .02,
It looks like your gauge is reading low, about 160-170 deg.
Mine when up to temp sits just below 210, 195-200 deg.
My 2.5 has just one temp sensor, but I have heard some
have two, one for the gauge, one for the computer. Change both.
As for the thermostat, from dead cold, remove the rad cap,
start the engine, look into the rad.
If you see water movement, it is not working properly.
If working properly, you will see no movement, then when
up to temp, the coolant will start moving and even overflow out the top.
There is no reason to run anything other than a 195 thermostat.
Mine is stock, but maybe with all the mods you have done,
your ecu is getting confused and staying in some kind of limp mode.
Is it throwing any codes?

[Jeffy]

Just my .02,
It looks like your gauge is reading low, about 160-170 deg.
Mine when up to temp sits just below 210, 195-200 deg.
My 2.5 has just one temp sensor, but I have heard some
have two, one for the gauge, one for the computer. Change both.
As for the thermostat, from dead cold, remove the rad cap,
start the engine, look into the rad.
If you see water movement, it is not working properly.
If working properly, you will see no movement, then when
up to temp, the coolant will start moving and even overflow out the top.
There is no reason to run anything other than a 195 thermostat.
Mine is stock, but maybe with all the mods you have done,
your ecu is getting confused and staying in some kind of limp mode.
Is it throwing any codes?

YJ's have two. One for the gauge is on the cylinder head next to #4 cylinder.  The one for the ECM is on the thermostat housing.

[95 Lowbuck]

YJ's have two. One for the gauge is on the cylinder hear next to #4 cylinder.  The one for the ECM is on the thermostat housing.

Yup, I stand corrected.

[jfrabat]

I know a lot of people run these with no issues not sure what I am missing.

Well, i am NOT one of those... My Jeep DOES NOT like high performance coils.  I toasted about 6 of them.  I even changed their location; my excuse was to get it out of the water and mud, but the reality is that I was tired of getting burns from the exhaust when changing them.  I went to stocker coils, and have not burned another one since.

But glad to hear this is resolved!