97 fzj80 strange issue, engine cooling, system lean (1 Viewer)

[Cruiser nancie]

Alright guys my name is matt ive had my cruiser for a year now no issues when i got it.
167,000 miles all maintenance maintained. Runs 15w40 cold air intake and high flow exhaust. Dual battery

So the issue is a get a system too lean code po171 and she runs around 190°f coolant and 90° to 100° intake hesitation at 3,000rpm or more and hesitates from a stop. This started about a month ago, at the time a code for o2 sensor 1 out of range, replaced. No other codes since then. Other that too lean

Typical system lean fixes and searches.
New fuel filter
New spark plugs
New distributor cap
No vacuum leaks anywhere under hood
Cleaned maf sensor
New 02 sensor
Replaced air filter
Wrapped intake tube in heat reflect wrap
Checked for exhaust leaks

Nothing i can find is wrong..
Someone else have this issue or maybe can think of something im missing for system too lean?

 

[BILT4ME]

Probably slim chance of finding someone with that combination. No one runs cold air intake other than a snorkel, and no high flow exhaust because it messes with the O2 sensors and computer.

@scottryana may be able to offer input as he seems to be the resident turbo and computer guy.

 

[half k cruiser]

Did you ....
-check the timing ?
-use the proper o2 sensor ? (Denso only for the post 95 trucks)

 

[bloc]

Where does your aftermarket exhaust start? After the cats?

If before, an exhaust leak can make the o2 sensors read lean when it draws oxygen into the exhaust stream.

 

[LINUS]

Did the lean start right after swapping to new plugs?

What color were the old ones & did you go back with the OE spec plugs?

Have you flat disconnected the battery & let the ECU start over & relearn? (shouldn't need to, but these are getting older & more picky)

I'll 2nd giving an 'evil eye' to that O2 sensor too.

 

[scottryana]

Tell us more about your cold intake and high flow exhaust. It is possible that you are just running too lean. Could also mean it is time to service your injectors.

 

[Cruiser nancie]

O2 sensor is denso oem,

Had the spark plugs for 15,000 before system lean pulled them all last week and they look fine,

Cold air was installed after system lean issue as there was a tare in the factory air tube ,

Exhaust is a jimmy rig, about 8 inches after the cats it goes through a step up to a 4 inch back over the axle to mufflers. But its been like that for a year and the system lean has been 2 or 3 months,

I have not cleared long term memory

Have not checked timing but have not changed it at all,


Ive been watching fuel trims.
Stft is about 0 fluctuates by 2% either way
Long term is at 19% idle 23% to 25% at 2500rpm parked and in the low 30% at wot driving

Showing 160hp and 295lbs
Temp around 175 with new thermostat

I show .08 lb/min maf
and .45 gph fuel flow. At idle

 

[Cruiser nancie]

Update..

Reset the computer
Runs like a turd
Ltft 0 of course
Stft at idle 19.5% same with throttle
Something i noticed witch might break the mystery..
At idle 19.5% but for a second when i hit the peddle any amount it goes to 0% then right back to 19.5%
I think i remeber from lincoln tech classes i remember that being a sign of a vacuum leak. Am i correct?

 

[Cruiser nancie]

Thought id post this info on my readings

 

[Cruiser nancie]

**** Found the issue, and the fix!

I decided to pull the fuel pump to see what the filter sock looked like and the condition of the pump/ sending unit.
Well i pulled it out and the pump just hung bu the wires. The hose clamp that holds the pump to the pickup tube for the sending unit had slipped up and the pump came off the sending unit assembly.
Honestly I'm shocked and confused on how the truck ran, just lean.
I never had a crank no start or a stall or anything that would point to fuel delivery issue. Fuel pressure was only 5 to 10 psi low witch even shocks me more.

If anyone has a system lean or engine starting problem. Pull the pump its easy took me 15 minutes to pull it out reattach the pump and put it back in the tank.

There is a trap door under the middle section of seats I did remove the driver side middle seat just for easier access.

I Have not had a single issue since. Rather I show
3% rich
230 hp
340 ft/lbs
13mpg city
15mpg highway
Air intake temp around 75°f with 85°ambient
All above factory spec