TOPIC: '98 Jeep TJ 2.5L - Canada

I will get this to the correct post yet!!

Just finished mileage check after first finished groove on a 98 Jeep TJ 2.5L. This was the 3rd time trying to get the angle right because of the venturi style throat below the plate. I ended up opening up the throttle plate about 1/16" to increase the angle and slid the cutter straight down the plate. 0 to 60 mph was over 1 sec. faster, 60 feet shorter, LTFT down to -8 from 4, and mileage up 25% (17.5 to nearly 22mpg). Plugged pcv and re-routed IAC to just over the throttle axle on both sides.

Also a note about cutting the idle re-route on this particular 2.5L: the original gasket was not very wide, and I did not check closely enough, so my first cut for the re-route bypassed the gasket on the narrow side, after the first inch, causing an early bypass on one side, and a vacuum leak on the other (too wide and past the gasket): my first cut. So I filled it. I looked more closely, traced the gasket on the bottom of the throttle body, and cut again. Because of the narrow gasket, plus the throttle body throat being about 1/4 " narrower that the intake plenum it sits on, the overall area of the mating surfaces is small. With a 1/4 " bit, you may have maybe 1/16" of gasket on both sides to seal, and with hand cutting, (mine anyway), I had less, so I ended up with another vacuum leak: my second cut. So, for my third cut, I first made a 1/4" aluminum plate to go between the TB and plenum, with the bore cut the same diam. as the TB bore: more leeway to work with on both sides. (To clarify: there was enough metal on the bottom of the TB to re-route with, but because of the plenum design being so slim, a lot of the metal of the TB was overhanging in the air.) I did have to re-bend the throttle bracket so my shift points were back to original because of the change of position and geometry because of the 1/4" aluminum spacer at the bottom of the TB.

I will start cutting deeper on the re-routes I think, because here now when it is above zero, I have no issues, but will I have issues at -20 to -30 C? I might. We will see.

Luke Wickenhauser
Gadgetman Saskatchewan

Hey Luke, Gadgetmannebraska here. These are awesome fuel trims.

Looks like you are learning fast.

I wish I could find more people with jeeps around here.

This is a great testimony.

Keep up the great work.

GadgetmanNebraska Aron Cheek

Hi Aron,

Thanks. What kind of mileage gains have you been getting with jeeps? I am working bugs out of my Cherokee before I give out final results. What I will say is that I bought the 4L Cherokee with the cat. cut out, but the downstream 02 sensor in place. The mileage changes that occurred after I put in a new cat. strongly suggests that on this jeep, the fuel trims are tied in with feedback from the secondary 02 sensor.

More once my rebuilt ECM gets in and the Cherokee rolling.

Have a great day!
Luke