Hi All - First real post here - asking for suggestions, advice, guidance, support, help, etc. for tuning up my Jeep. I've included as much information as I can think of.

Background in a nutshell:

The Jeep is a 1990 Wrangler with 4.2L straight six with three speed automatic. I put a Howell TBI kit (emissions version; 1227747 ECM) on it in 1990. Starting and driving improved tremendously but some problems persist. Most noticeable: the thing STINKS terribly, especially at idle, like it is way too rich. Upon startup a lot of white smoke comes out the exhaust. It isn't oil and it isn't coolant. I used to think it was condensation in the exhaust, but it lasts too long. I now get the impression that it is "smog" from unburned fuel. Recently I immersed myself in learning about TBI, and I bought a Moates AutoProm setup with TunerPro RT. Datalogging revealed low BLM (108) at all RPMs at lower loads, although they get close to normal (a few points on either side of 128) from 50 to 80 MAP (and go low again at 90).

Shortly after initial installation I contacted Howell and got a new chip. It didn't make a difference that I could tell. With my new AutoProm I read both chips - initial and replacement - and found that the new chip had somewhat lower values in the VE1 table, and the BPW was reduced from 185 to 181.

Interestingly, I found that the throttle body is a small bore one from a 2.8 or 3.whatever - I acquired one from a real 4.3 and the bores / butterflies are bigger. I imagine it has real 4.3 injectors, though, since the BPW was set at 185, which seems right for 45# injectors for a 4.3L.

Other relevant information: I have an unrestricted cold air intake connected to the small throttle body and stock, low flow Jeep intake and head. I have a 2.25" exhaust with a high flow (clean) catalytic converter, and a header. The engine has been rebuilt (overbore is 0.060"); compression is around 8.8-8.9; camshaft is a Comp Cams design intended for lower RPM use; and the distributor is an HEI conversion - originally a DUI, but more recently a Summit Racing version (not controlled by the computer).

So...


I have a theory about my RICH problem. I am guessing the small throttle body represents some restriction, lowering my VE, especially considering the improved exhaust flow and (partly) the camshaft. This isn't the only problem, but I guess it's part of it.

To fix this thing, I have a few different directions to go. Ultimately, I will put on the 4.3 throttle body and tune it from there. More immediately, however, I need to do a little bit to the existing setup. My main questions at this time are:

(1) Should I further lower the BPW a little bit? This sounds like a band-aid fix, but I see that it's done sometimes.

(2) Should I adjust the VE1 table based on my BLMs? I am guessing this won't be a one-time deal, since my minimum BLM is 108 and I have no idea how low it would really go.

(3) Would I see a benefit in lowering​ my fuel pressure?

(4) What chip and buffer addresses do I use when I write the 27SF512 chip? (I installed the G2 adapater in my computer.)


A few points to make:
- Fuel pressure is 12.0 and super steady at all RPMs; return pressure is zero.
- Vacuum at idle is about 17 inches and very steady.
- Timing is 8 degrees BTDC at idle, and the mechanical curve (NOT computer controlled) is moderately aggressive; vacuum advance is set to the point just before detonation.
- The spark plugs are black.
- The EGR is vacuum controlled and seems to work right.
- The sensor readings (MAP, O2, TPS, Coolant) and voltages make sense and move the right direction when viewed on my scan tool.
- The Jeep actually runs pretty smoothly - it just stinks bad, drinks gas, and has less power than it should.
- TunerPro RT displays my BPW as 34.9 and calculates my injector duty cycle to be ~95% at 800 RPM, all the way up to 314% at 2800. I have no idea where these number come from or what they indicate.


Thanks VERY much for any help anyone may offer. I will be monitoring this thread closely and updating it when I make progress.

Dan.