This is an update.
So I decided to re-groove the 92 Jeep Cherokee. I tried using JB Kwik, but when blowing out debri, the dried expoxy blew loose. So on the next try I used JB Weld. But prior to using it I washed out the area with Purple Power degreaser. I waited a day before trimming, sanding, & shaping the dried JB Weld. Next time I have to re-groove, I think I'll use JB Kwik again, but make sure to use the degreaser first. I don't like having to wait a whole day for the expoxy to cure.
Anyway, my new groove looks a little better than my first one, although I'm still seeing lots of opportunity for improvement. The good thing is that the groove is closer to the throttle plate. But when I look at RD's groove on his 94 Explorer, I can see that mine needs to be smoother and more consistent from bore to bore. Here's the pics of the groove:
So in using the flashlight test, I discovered that I went through the TB wall in two places which happen to be in the cavity of the IAC valve. So I removed the IAC valve and applied JB Kwik in the offending holes. But then I became curious as to why an oily residue was present inside the cavities of the IAC valve. See photo:
So I reassembled the IAC valve and re-installed the TB. I took the engine through the ECU re-conditioning process. RESULTS! Much more power than the first time around. Dan said I would get better power and better mileage if the groove was closer to the throttle plate. I haven't put on any appreciable miles yet, but he was right about the increased power! Especially in third gear (5-speed manual). Acceleration in third gear is noticeably improved. This '92 Cherokee 4.0 in-line six with 275,000 miles will exceed 85 mph in third gear! How much more, I don't know because 85 mph is maximum indication on the speedometer (I hate those 85 mph pegged speedometers). So that's the good news so far.
Please remember that on the first go around, I capped the crankcase ventilation port and allowed the exit hose to hang down toward the road.
When I got back home after the ECU conditioning process I noticed oil vapor blowout on top of the valve cover, both on the front end fresh air intake and on the rear end exit port. I guess I need to replace both of those ports on top of the valve cover. See photos:
You can also see oily residue around the oil filler cap. Guess I should replace that as well:
This oily residue on the valve cover is unusual. I don't get that with my normal easy (gas-saving) driving. But I had just finished the ECU conditioning process, including the piece that Ron describes as driving the vehicle like I had just stolen it, although I could only guess at that because I've never actually stolen a vehicle. But having been a cowboy driver in my teen years, I knew how to push it to the max. Hence, oily residue! This residue also showed up inside my air filter box. See the next two photos depicting the crankcase fresh air intake hose running from the air filter box to the top front end of the valve cover:
So now take a look at the oily residue inside the air filter box:
So at this point, it is obvious why I saw oily residue inside the IAC valve cavities! So my question is, "Why am I getting oily residue backward through the crankcase fresh air intake hose?" Any one care to venture a guess? I am clueless. Could this be a result of capping the crankcase ventilation vacuum port and allowing the exit hose to hang toward the road? With this now passive system, apparently oily residue is being forced back into the air filter box via the fresh air intake hose. I do have an option of "teeing" the crankcase ventilation exit hose to the hose exiting from the Evaporative Emissions Control canister which connects into the front end of the throttle body. Would this provide a little more vacuum for preventing the backward flow of oily residue through the crankcase ventilation fresh air hose? But even if this backward flow is eliminated, would I not still be getting oily residue back into the TB via the crankcase ventilation exit hose which is now "teed" to the the hose coming from the Evaporative Emissions Control Canister? Bottom line: seems like there may be no way to prevent oily residue from re-entering the TB. Thoughts and comments?
So I turned my attention to locating any vacuum leaks. Using the Mighty Vac, I found that the only vacuum leak shows up in the hose leading into the climate controls. Inside under the dash, I noted that I have four vacuum solenoids controlling several gates or doors for climate air flow. I noticed that all four actuate properly. So I don't have a clue as to how to find the leak in those hard-to-reach areas. This may be a piece that I have to sturn over to my mechanic.
In following one of the vacuum lines that may be related to the 4wd function, I located a small tank perhaps 6" long and 4" high. It seems to have no outlet, but I can't really tell because of its remote location behind the right front bumper. It seems to be some sort of vacuum resevior. Here's the photos. Can anyone tell me what this is? The hose leading to it tests fine for holding the vacuum properly.
Another question relates to the brake booster. The vacuum on this line maxed out at 20.5 inches, but it holds firm at that level. I also accomplished the tests described in the Hanes maintenance manual for air tightness and proper operation and it passes those tests. So while there is no leak here, I'm wondering why I'm not getting at least 22 inches. Any guesses? Is 20.5 inches satisfactory?