Hello, looking for some insight or experience with this one. A little background truck had a cracked head now has 2 new heads 2 new 02 sensors complete upper gasket set, plugs, wires, vac lines, ran great after job still seams to although a little down on power. has had about 1200 miles since the work and truck has 140,000. problem occured in last 200 miles. no other lean codes present. has fresh fuel filter. thanks in advance Tim

 

With all the work you've done & the delayed onet of the lean bank 1 trouble code it would suggest a vacuum leak affecting bank 1, to me.

The pushrod 4.0L is known to be prone to intake manafold gasket leaks, so maybe one of the replacemet gaskets got messed up, or a intake manafold fastner has loosened up after a few heat/cooldown cycles. So maybe check the intake manafold fastners torque.

Maybe even a bad O2 sensor, or maybe one that got a whiff of left over coolant from the work that was done, or maybe the O2 sensor is just lazy.

Just because they're new, doesn't automatically make em good, make them prove themselves.

So look for a visual signs of a vacuum leak, maybe even rig a "propane sniffer", with a length of tubing, with something like a sports needle as a probe & see if you can find a intake side leak. The engine rpm should increase, as it gets a whiff of the propane through the leak. The needle probe, will allow you to fine tune your search & the propane is engine & sensor safe.

If all that comes to naught, test the bank 1 O2 sensors switching rate & see how it's doing.

Let us know what you find.

 

You might want to take a look at the fuel injectors.. I'm wondering if you might have a restriction in one of them. Disconnect the electrical connectors and check the resistance at both terminals on each injector. I don't know the exact specifications, but what's important is they should all have roughly the same resistance readings. If you find one that's unlike the others, then it is bad. Also you might want to remove the injectors and clean the tips real well. I've heard stories of people who have had great success dipping the tips in CLR overnight.

Another thing you can do is using a digital tachometer, unplug the IAC and let it idle. Then one by one unplug each injector and note the RPM decrease. If you find one injector that makes less of an RPM change when unplugged, then that's a likely culprit.

You might want to find a scanner that's capable of displaying data parameters. Just because only BANK 1 lean is set, doesn't mean BANK 2 isn't having issues either. I've found that almost every LEAN code set on these is caused by vacuum leaks. I know it's highly unlikely in your case, being a lot has been replaced, but you can't ignore this possibility. Typically a vacuum leak will cause both banks to be lean.. but I've seen some that, for example, make bank 1 lean enough to set a code, but bank 2 (while still lean) was right on the edge, but not quite over it. You need to examine your long term and short term fuel trim data readings, and draw your conclusions from that.

Good luck.

 

You may also want to do a fuel pressure test, could be as simple as the FPR. Just my 2 cents

 

Good point. I was thinking along the same lines, that maybe it's really both banks that are lean.

And aside from gaskets, I can't think of anything on the passenger side of a 4.0L OHV that might cause a lean condition specific only to that bank. I suppose if there was a problem with the hose connection between the oil fill port on the valve cover and the air intake tube...?

 

It's possible... maybe causing atmospheric pressure to keep the PCV valve slightly open all the time.. creating a slight vacuum leak. I'd definitely fix that and go from there.

Good luck.

 

hello all thanks for the great ideas, i do have a new injector set i may install and i'll dig deeply into it on thur checking o2 readings and double checking all vac lines again and let everyone know what it turned out to be. Thanks

 

Please do keep us informed.. I'm curious as heck!