jeep renix keeps falling out of closed loop

[PJG1173]

So I finally got my daughters 88 jeep wrangler running and I've been driving it most of the week. the other day it started to develop a pop out the exhaust everyonce and a while in between shifts. it dieseled on me twice when I shut it off. it is a 88 2.5L TBI motor. I borrowed my buddies snapon scanner and I'm able to see good amount of data. bascally when I start it it will go into closed loop and stay there until the engine gets up to operating temp. then it will switch to open loop and lock short term BLM to 128 but long term stays at 172. I can watch the o2 voltage swing back and forth normally. If I take it out for a drive it will stay in open loop once and a while it will go to closed loop, but won't stay there long. just looking at the o2 volts everything looks like its working. I had a buddy tell me that he thought that jeeps idled in open loop, but I can't find much on this topic. I think mainly because not many people have the capabilities to read data from these things.
does any one know what the stratagy jeep uses on these things for determining when to go closed loop? I don't know how old the 02 is so I am going to replace it for good measures, but I don't want to just start throwing parts at this.

[EagleMark]

then it will switch to open loop and lock short term BLM to 128 but long term stays at 172. I can watch the o2 voltage swing back and forth normally. If I take it out for a drive it will stay in open loop once and a while it will go to closed loop, but won't stay there long.
Something is wrong? Could be faulty O2, if it hasn't been changed in 50k or so it won't hurt and you can see if it's tan or white or black just like plugs, with those INT and BLM and open loop should be black if fuel pressure was correct, white if not... Once you disconnect batt and loose the learn it may work again, right now it seems pegged adding fuel and went open loop... lean will cause the diesel, pop... I'd be checking fuel pressure and replacing fuel filter to see if that caused why it wanted to add so much fuel.

[PJG1173]

I replaced the o2 sensor. the old one was white. its been raining off and on this week and I've been real busy at work so I haven't had a chance to get out there and mess with it again. I'm planning on changing the fuel filter this weekend and see if I can "T" into the fuel supply line to get a pressure reading. This is the first time the Jeep has been driven in about 4 1/2 years, so I'm thinking there may be some gunk somewhere. Plus the alternator just crapped out on it so thats another $80 I have to drop on it.:mad1:

[EagleMark]

4 1/2 year old gas has been stale for 4 years... drain or fill tank, it will get better...

[PJG1173]

4 1/2 year old gas has been stale for 4 years... drain or fill tank, it will get better...

Unfortunatly that was the first thing we did while the engine was at the machine shop. it was clean as a whistle (to my supprize) ended up using the 4 year old gas in the lawn mower... we must have go too excited putting the motor back in and forgot to change the fuel filter. here is all we replace getting it running and driving to this point.

plugs
wires
cap
rotor
distributor (from PO thought that was his problem)
water pump
radiator
radiator hoses
t-stat
overhauled top of motor (bent valves)
timing chain
brake rotors
brake pads & shoes
vaccum lines
o2 sensor

on the to do list
alternater
fuel filter

[EagleMark]

Back to basics. Still will be a cheap rig at this point and maintained.

Newer cars and sealed tanks seem to hold gas longer with no air? May have been lucky and not been ethanol enhanced from that long ago? I just fixed the neighbors lawn mower that worked last summer and sat all winter with 10% ethanol gas. Pulled fuel bowl and could see the water bubble in bottom of gas and corrosion starting on carb! It was one year old! Always use non ethanol fuel in lawn equiptment... can also run 4 degrees more timing with 93 non ethanol then 87 octane but only 2 degrees with 93 octane with ethanol... Shhh!

[PJG1173]

just an update. I swapped the o2 and it is staying in closed loop now. unhooked battery to clear computer and i'm still seeing blm's in the 150's. the backfire between shifts has almost went away its more like a poof now insted of a pop. the weather wasn't too friendly this weekend to change out the fuel filter and money has been tight lately to get the stuff I need for the fuel pressure gauge. Also while using the snapon diagnostics i noticed the CTS was reading about 30~40* higher than the dash gauge and the MAT sensor. the scanner said the MAT should read 10* lower than the CTS at idle. could this be causeing some of my problem? another special order part... this thing is starting to live up to its name "Just Empty Every Pocket".

[EagleMark]

"Just Empty Every Pocket".:laugh: I hate when that happens...

I'd not even consider a stock factory dash gauge as a factor, so where does that leave the scan tool readings? If the scan tool is reading close to thermastat and MAT is close then I don't think that is the issue. Now if it's 30 to 40 degrees of then yes theres and issue!

Still sounding like a fuel pressure/deleivery issue to me? Other opinons always welcome...

[PJG1173]

the dash gauge is reading normal operating temps. I have a 185 tstat in it and can see when it opens on the dash gauge about 190*. the scan tool was showing coolant temp 220+* while the MAT was showing 180* and the dash was 190*. so I'm pretty sure the CTS is bad. I still haven't ruled out a fueling issue though, but I know the CTS being off will affect fueling too.

[EagleMark]

See that's why I have a lazor heat gun to see what temps are actually near what sensor. So where is CTS in relation to thermastat? It may be right for Jeep. But on Chevy the CTS is in waterflow right next to thermastat so temps make sense, if you put it somewhere else it get's the wrong temp. I don't know what the jeep is supposed to read.

Now if MAT is supposed to be 10 degrees lower, well it's 30 degrees lower so yeah sounds like CTS is off? How long this thing been sitting? Whens the last time it had a flush? Wondering if CTS flow is impeded in some way? If it's way overdo you could give it a good flush before buying a CTS? Take it out and flush in that hole, clean CTS and reinstall? That's all free... oh is CTS temp correct when engine is cold?

HTH!

[PJG1173]

It sat for 4 1/2 years that I know of. cooling system has been flushed and I cleaned the temp sensors when I did the head gasket. the sender for the gauge is in the head at the back about 3 inches from the CTS.

[EagleMark]

Hmmmmm? Since it's no where near the thermastat I wonder if that temp is correct?

Free test is what does CTS read on scanner cold? Should be what outside temp is...

[PJG1173]

I had to give the scanner back to my buddy. I replaced the fuel filter and the CTS yesterday and it seems to run better. Idle quality is better when up to operating temp, so I'll see how it goes in a couple of days I'll borrow the scanner back and check the CTS and BLM's. whe I changed the filter I poured the fuel out the inlet side to see what color it was. it came out with a slight tint of purple:confused: not rusty brown like I suspected.

[EagleMark]

Never seen purple gas?

[PJG1173]

the only purple gas I've seen comes in a blue can and is quite expensive.

[EagleMark]

Wonder what it is? Well if it's running well enough to empty the tank and get a fresh full tank some of these issues may go away.

I just changed a fram TBI inline fuel filter and it rattles? Looked inside and filter is not attached to can... so much for those injectors...

[PJG1173]

IDK, that was the second tank of fuel I ran though it since we got it running. the fuel from the outlet side of the filter was clear with no color to it.

[EagleMark]

Well whatever was purple was bigger then 3 micronds...