gmrulz4u Posted June 1, 2003 Report Share Posted June 1, 2003 I know I've been running rich for sometime now, so recently I decided to hook-up my OBD Scanner and see what my Block Learn values were for the following 3 states: 0 - Idle (0% throttle) 1 - Any throttle 2 - Coasting (0% throttle) For those that don't know, Block Learn is just a term for how much fuel the ECM is commanding to be added or taken away to remain as close to the perfect A/F ratio(14.7-1). It does this by either increasing or decreasing the amount of time the fuel Injectors stay open. What I noticed was that both zero throttle values, idle and coasting without throttle, were quite a bit lower than when there was throttle ie. giving gas via the pedal. In some cases there's a differnce of about 10-15%, meaning when I let of the gas pedal, the ECM would immediately try to take 10-15% more gas AWAY because the O2 sensor was telling the ECM it is seeing more Rich than Lean flags. My O2 sensor is working perfectly(I can see it), and it's only 6 months old. So what I need for you guys to tell me is what happens when I let off the throttle? For example, I know that the EGR valve is supposed to shut completely with 0% throttle, but what else is supposed to occur? Because obviously something that is supposed to stop giving gas or fumes when there's no throttle is NOT working correctly. I know an EGR valve that is "stuck open" would cause a rich condition because it would be circulating exhaust gases ALL the time, but wouldn't I experience more problems than this? I figure it's something related to emmisions components like PCV, EVAP or EGR etc...but I don't really know for sure... It runs a little Rich all the time, but it's excessively worse when the throttle is completely shut and at 0% opening. Anyone with suggestions as to what this can be?? THANKS:) By the way, it's an 89 Supreme w/ 2.8L... Quote Link to comment Share on other sites More sharing options...
JS91Z34 Posted June 2, 2003 Report Share Posted June 2, 2003 sticky EGR or leaking injector. Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted June 2, 2003 Author Report Share Posted June 2, 2003 Thanks man! So to clean the EGR valve, do I just buy some Throttle Body Cleaner and spray it all over the EGR components or something?? I remember replacing my EGR valve with a brand new, and expensive, one about 2 years ago...haven't touched it since... Quote Link to comment Share on other sites More sharing options...
Vegeta Posted June 3, 2003 Report Share Posted June 3, 2003 Wasting your time. There are seperate values and calculations used for cell 0 1 and 2. I have seen cars that idle at 100 BLM 76 int (mine), then are 126 BLM 128 INT at cruise (well its all over, 124-128 with int all over because i havent tuned it yet). Decel hits 120 BLM. Its normal. You would have to change the coding to make the BLM the same across all cells, via perfect tuning. Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted June 3, 2003 Author Report Share Posted June 3, 2003 Wasting your time. There are seperate values and calculations used for cell 0 1 and 2. I have seen cars that idle at 100 BLM 76 int (mine), then are 126 BLM 128 INT at cruise (well its all over, 124-128 with int all over because i havent tuned it yet). Decel hits 120 BLM. Its normal. You would have to change the coding to make the BLM the same across all cells, via perfect tuning. That may be true. But just because something is "normal" doesn't mean it's OK. I wouldn't be as picky if the ECM was able to compensate for BLM's below 100, but it's not! So even if the engine keeps getting more and more fumes or raw fuel, and starts running richer and richer, the ECM will never let the BLM go below 100, even if it wanted to. GM says "normal" readings are 128 +/- 10 counts, so anywhere from 118-138, not 100. 100 is 28 counts, which is the same as 22%. I don't think anyone can honestly say that an ECM commaning 22% LESS fuel than it's supposed to when optimum, is "normal"? I'm not saying it's a HUGE deal, but there's no denying the fact that my car runs rich. My car hesitates a lot. Idles poorly, worse when hot. My gas mileage is poor etc...etc...I KNOW it runs rich, I just don't know why yet? THANKS:) Quote Link to comment Share on other sites More sharing options...
Vegeta Posted June 3, 2003 Report Share Posted June 3, 2003 Where did you say you were at 100 BLM anywhere. Best of luck to you on changing it. Did you even notice it without your scanner? Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted June 3, 2003 Author Report Share Posted June 3, 2003 Oh shit, sorry Vegeta. Yeah, my BLM's go down to 100 if I do a lot of driving, like a half hour or more. First, cell 2(coasting) goes to 100, then cell 0(idle) goes to 100. I haven't seen cell 1(throttle) go to 100 yet, it is usually between 110-115. THANKS:) Quote Link to comment Share on other sites More sharing options...
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