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Discussion Starter · #1 ·
Hello everybody,

About a year ago, I had my stock 4.2 converted to become fuel injected using the Howell TBI kit. It ran like a dream, until recently. It would start fine, but once I got moving and into operating temp, it would idle very rough and while I was driving, I had to drive in a lower gear than usual to prevent it from stalling on me(For example, I was able to drive 55mph in 5th smoothly, once the issue arose, it would stall, or almost, at the same speed and same gear, making me have to drop to 4th). Basically, a lack of power.

I also noticed when I start my YJ, black liquid comes out, just little drops though. And if I give it gas, it would idle very rough, from 800rpm to 500rpm, afterwards. Then it would either resume idling rough, or stay at 900-1100rpm(Like it would before the issue arose)

To those that don't know, the Howell TBI kit uses GM parts, meaning I am able to check error codes because of the GM ECM. I checked the codes, I got error code 44 and error code 45. I did some research, code 44 indicates a lean condition, error code 45 indicates a rich condition. Culprits may be a bad o2 sensor. I also noticed, my exhaust resonator has a crack, makes me wonder if that can be an issue.

Besides the o2 sensor possibly being bad, what else can be some culprits? Where are the o2 sensors on the 4.2, by the way? I plan on changing them myself. Is the Jeep really running rich and lean at the same time?

Thanks
 

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Discussion Starter · #2 ·
Okay, I swapped the o2 sensor, code 44 is gone. The YJ drove very well until the CEL came back on. Code 44, is now the only code. It runs very poorly, idles erratically and there's a lack of power
 

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Howell has a support line that's very helpful, I used it years ago for my Grand Wagoneer.
 

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Back to the basics.
From my GM driveability manual:
CODE 44= Lean exhaust all engines
O2 sensor wire contacting exhaust manifold
Ck for intermittent ground in wire between connector and sensor
Fuel contamination- Water in fuel
Fuel pressure- Low fuel pressure
 

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Okay, I swapped the o2 sensor, code 44 is gone. The YJ drove very well until the CEL came back on. Code 44, is now the only code. It runs very poorly, idles erratically and there's a lack of power
Are we dealing with code 44 or 45??
 

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Code 45= Rich exhaust
Fuel pressure- High pressure will cause rich condition. ECM can deal with some increase. If it gets too high, it will set Code 45.
Leaking injector
HEI Shielding- Open ground in CKT 453 can induce noise that confuses the ECM into thinking the engine speed is higher than it is causing it to over fuel the engine.
Canister purge- Check for fuel saturation
MAP sensor- An output that causes the ECM to sense higher manifold pressure( low vacuum) can cause the system to go rich. Disconnecting the MAP sensor will allow the ECM to set a fixed value. Substitute a different MAP sensor if the rich condition is gone when the sensor was disconnected.
Pressure regulator- Check for leaking diaphragm by checking for liquid fuel in the vacuum line to the regulator.
TPS- An intermittent TPS output will cause the system to go rich, due to a false indication of the engine accelerating.
 
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