Hi All:

(Been gone awhile, but I'm back now)


I have an old Howell system (10-11 years or so) on my Jeep Wrangler. It's a fuel-only system that I am trying to update. One of the things I did recently was get an EGR solenoid and hook it up to (I think) terminal A4 (or whatever the diagram said for the 1227747). The idea, as I understand it, is that the ECM grounds the circuit and causes the solenoid to open, so that vacuum from a ported source goes to the EGR valve. I have a negative pressure valve and I put this together in accordance with the FSM.

The problem with this is that I really didn't test it before I datalogged with it. Right after I hooked it up, I placed a vacuum gauge on the outlet of the solenoid. As I revved the engine, the vacuum would increase (after I went past about 1000 RPMs), then, when it got to about 10psi or so, the solenoid clicked and the vacuum went to zero. Now, I should have stopped right there and logged some, but instead, I made up a new chip with some adjustments to the EGR settings. More on those in a minute...

Two things happened during my 30 minute drive:

(1) The fuel became VERY rich. My BLMs were all 94's except near idle, and my integrators were around 118 or so, suggesting that the BLMs could go even lower. I had previously changed the BLM limit so that values could go below 108. Now, the engine ran pretty smoothly, which told me that either the original EGR system was on all the time and the switch to ECM control fixed it (not true - see #2) or there was no EGR happening at all).

(2) I had wired an LED in parallel with the two wires going to the solenoid (inside where I could see it) and it never ever not once came on, saying that whatever I changed on my PROM probably messed stuff up.

Settings (all scalars) I changed before driving were:

> MAP threshold EGR ON: from 255 to 40 - my thinking was that 255 eliminated EGR, but maybe 255 means it's enabled at any MAP?

> RPM Min for EGR%: from 1000 to 1300 - just because it sounded right

> On Hi VSS: from 0 to 74 - not sure what the number means, but I ASSUMED "Hi" made me think that the number needed to be above zero MPH for the thing to work. Maybe I'm thinking backwards? Will it work right if this is zero?

> On Hi TPS: from 1.95 to 3.3 - I ASSUMED that this meant EGR would not work above 1.95, and since I spend a lot of driving time ABOVE a TPS of 1.95V, then 3.3 sounded about right. Is this backwards like my 'On Hi VSS' thinking?

> Min kPa for EGR% - from 69.92 to 40 - figured this would make EGR work more often, but might change it back to the higher number.


If anyone can PLEASE explain this stuff to me and tell me where I went wrong (or right), I would GREATLY appreciate it. The reason I am changing some of these values is this: I know Howell disabled some things in their setup, but I don't know what I need to change to get these functions back (like EGR, ECM controlled timing, whatever else). I even discovered that even though I had a California kit which should have had a VSS, the wire in the loom did't go to the ECM - it just disappeared in the tape somewhere, and I had to put a wire in the connector for it. Same thing for EGR.

I have made my VSS work - I'll put a little write-up on the forum sometime since it's a little unorthodox. I am attacking the EGR now, and I plan to change my timing to ECM control next. (If anyone can point me to a good write-up about the timing change, that would be great. My searches usually show me something about going the other way.)

PLUS: is there a better way to learn this stuff, like a book or something? I have the FSM, but it's not much good for things other than wiring and troubleshooting. I would LOVE to see a write-up on what every little scalar and table in the BIN file does. Maybe I'll do that one day when I learn more.

Anyway, I anxiously await your answers. I have to make a new fuel table so I can drive to work tomorrow.

Dan.