TOPIC: '98 Jeep TJ 2.5L - Canada

Looks like I will have to try again:

More photos:




This is the gasket that I made to make use of the full area of the plenum and throttle body base.



This shows the small area on the plenum to gasket mating surface





This shows the final idle bypass cut. Note the epoxy fill where I tried the first two times or so and went past the gasket because of the small area to work with. I needed a fairly wide and deep path because of the colder winter weather. I used a 3/8" bit and went down about a quarter inch.

Luke

Hi Luke,

I think this is the Youtube video that was posted earlier...

a bit lengthy but some good information



Karl Fortner
Tacoma, Washington

Hi Luke! I don't yet know enoughb about computer stuff to answer your question about the fuel trims. I always assumed that the more in the minus values ST and LT went the better.

I apologise if you told us earlier, here goes: Hunted down/killed all possible vac. leaks? O2 sensor(s)switching fast enough, Ignition system in top condition (plugs w/ gap opened 20%, cap/rotor/ wires top condition). PCv re-route done?

On the TB base in last pic: the one I did last March had same issues on gasket seal. Outboard the throttle shaft both sides is a round shallow hole--I filled in w/epoxy to increase sealing area. One on yours bottom of pic perilously close to IAC re-route groove, also might be a nick next to a square depression might fill 'em in...

I realise time invested in this TB; but if epoxy proves an issue in filled Groove, might want to score another TB and start over w/ all gained knowledge. I wonder if you have epoxy bonded to previous epoxy if delamination might occur there; I dunno... I did two grooves today, a new one and a re-cut on an old one, and I sure am glad I got a Panavice, didn't you say you had an old one? 2 hands on the Dremel sure beats 1, for me!

That's what I can think of for now, good luck, Luke, keep us posted buddy! PS you know what needs to be With You...LOL!

TracyG Gadgetman Reno

Hey Tracy!

When I got the higher fuel trims, I thought that it may be a vacuum leak, so I un-plugged everything: even the brake booster, and plugged all vacuum ports on the intake with new plugs. (Out in the country here on the backroads, traffic is very sparse - I do not recommend disconnecting brake booster and driving on travelled roads.) I checked the plugged PCV line and it held vacuum, but plugged the manifold connection anyway. The fuel trims remained the same at road speed. The spark-plugs are new and gapped, the rotor and wires weren't touched, but this fuel trim change happened within 2 runs. This morning I will check for de-lamination, and try again, but I was thinking along the same lines of getting a different TB as this, after 5 tries, is all epoxy!

Re: the idle by-pass being perilously close to that round blind hole, since the hole is blind, I left it, and I could because I allowed for any major discrepencies by making a full-area gasket to mate with the aluminum plate (just note pictures) and by doing so, I have all the area around the blind hole that is sealing the bore from outside vacuum. I had the same gasket and plate for my first attempt that gave me -8 long term fuel trims.

Go figure!

One note that I forgot to mention: on the second-last try on this throttle body, (I actually did 6), I tried one more experiment: I opened my throttle plate up to 28 deg. (using a measuring jig) and blocked my throttle open at that point, and made the groove sliding down the face of the throttle plate. It was a beautiful, uniform groove done at 28 deg, but it was a good 3/4" away from from where the idle position was in the centre. I reset the ECM, and on the highway run, the fuel trims still sat about 0 to -1. Expecting better, I didn't do a mileage check and instead did the last groove as described previously. Looking back, assuming my mileage gains are legitimate with the '0' fuel trim, perhaps the mileage may have increased with this far-off 28 deg. groove. I don't know.

Keep experimenting!

Luke

Wow Luke 6 times on one TB!! Yup get another one. I adopted the revised bit angle when Ron told us about it. I re-grooved a couple of TB's I'd done, used it on my second shot of my Subaru's iron throttle base, and used it every time since Ron announced it. I also am using the throttle plate shaping mod (see Documents section) every time, and sanding the leading Groove edge too. I'm learning and improving...

If ya git another TB, I'd use new angle for bit, and incorporate everything you have learned so far on it.

If McGyver is hanging around your place again, send HIM out searching junkyards in your region, tell him no more bailing him out 'till he brings ya another TB!


Groove on!

TracyG Gadgetman Reno

Luke,

By using the throttle plate in this fashion (as a jig) you effectively cut the efficiency of the mod by many levels. The Groove MUST be as close to the plate as possible.

You must learn to use your hands instead. The taper at the end of the bit is there for a reason. To give you a reference point. Simply increase the angle by ~5 degrees incline.

Get yourself another throttle body and try again. This time, don't take the easier path, as this is affecting the results. Without The Groove in the proper position, you will not get the results we are getting.

I am glad this thread is up! It may help someone else avoid the same mistake.

Hi Ron,

I must explain this a bit more effectively. I was using this jeep as my experiment: I wanted to see first hand the effects of the groove in different positions, etc. I understand the concept, and all the recent grooves that I am doing now is with the greater angle: I try to get it around the 25 deg range or so.

I found the problem with the mileage and rough idling: it was just spark plugs gapped on the wide side: they worked well for the first 3000k or so and then I am guessing from spark erosion, widened beyond the tolerances. I re-gapped at about 20% over, and checked everything again: no de-lamination. Since it was off, I filled, and re-grooved with about a 28 degree angle. I will be posting results soon.

Thanks Ron.

Results: Average 22.5 to ~23.6 mixed driving, long and short distances. The LTFT is at 0, and I am starting to think that my gauge is faulty (Long term fuel trim was at -8 first, before the scanner hit the concrete). Once I get another scanner I will recheck the trims.

So, 28.5% to 34.8% increase in mileage with the new angle, compared to 25% increase with old angle.

Keep Groovin'!

Luke

Excellent Luke! You are getting somewhere good w/your Jeep!

TracyG Gadgetman Reno