One more thing, measure the resistance of all injectors. Yours are supposed to be 14.5 ohms which is the correct rating I believe for OBD1 XJ'S.

 

Any recommendations on a wide-band to get?[/QUOTE]

I like to use the aem 30-4110
I use NTK o2 sensors

 

Ordered the wide-band and fuel filter this morning. Will get here tomorrow. Have an apt to have the bung installed already. I’ll let you know what I find as soon as I get it sorted. Thanks again for your help.

 

Also, I dont have a multi-meter with me. It’s at my house in Californian but im in Ohio until early Sept.

I have a new (stock) fuel pressure regulator for the rail. I can swap that out if you think it’ll help.

 

If you've tested the fuel rail pressure and it's fine I wouldn't change the regulator at this time.

 

I get the sensor bung installed on Wednesday. I got a the AEM 30-4110 kit from Amazon but it’s obviously been opened before. Seems to have everything with it but we’ll see if the sensor is any good.


Now that I think about it, can I just pull the 02 sensor and use the exiting bung for the AFR sensor?

Just for while I’m figuring out how lean Im running.

 

You will need the narrowband for the ecu to achieve closed loop. Since the problem happens in closed loop you will need it.

 

I was afraid you’d say that. Well, I’ll have it sorted come Wednesday evening. Thanks again for the help.

 

Got it installed finally. Took it out for a drive and…

AFR is jumping around a bit. Between 4.5 - 5.5

 

I hope you mean 14.5 to 15.5

 

oops! Yes 14.5-15.5. Thanks for the correction.

 

Well that's normal closed loop readings. What happens to the afr while the problem is happening?

 

A side note. Your reading is not the actual AFR if like 99.9% of us your burning 10% ethanol. At 14.7 (ideal at idle, warmed up, 100 % gas) on your gauge you're really around 14.1 with 10% ethanol. That's okay, because your gauge is reading based on the lamba valve, and so just assume 100% gasoline and compare those numbers. I'd be interested to see your numbers at cold start up, under mild acceleration, cruising, and coasting off throttle. Good luck, hope this gets figured out.

 

Well, Im a bit under the weather. I haven’t driven it much. I’ll know more tomorrow. I took it for a spin just to see if the sensor was working and initially, it was all over the place. When I first start it up, it was closer to 13 and change. Then as it warms up, it gets a bit leaner and the wideband reads around that 14.5-15.5 mark. If Im on the highway gong 85, same thing 14.5-15.5…. When I down shift, it’ll ping all the way to the right off the chart and I get 3 dashes on the readout. And that’s when she give me a little gurgle and pop sometimes just a gurgle and no pop. As soon as I take it out of gear, it levels right back to the high 14s lo 15s whether I have my foot on the gas or not. If I keep it in gear and give it throttle, it goes right back to the 14.5-15.5.

 

The 13 afr is typical for after start enrichment. On decel your ecu commands open loop and stops pulsing injectors. With no fuel to react with the oxygen you get a lean afr beyond the readable voltage ( 3 dashes)

Are you getting an exhaust pop or are you truly backfiring out of the intake? If you have a timing light the 4.0L has a degree indicator. Remove your efan and you can verify your timing.