Never mind, I just assumed, for some reason, that you were running stock valve train. My bad.

 

I am pretty sure that I do not have any exhaust leaks before the oxgyen sensors. I have not spotted any carbon streaks coming from the headers anywhere nor do I really hear any leaks. I do have pretty low gas milage in the city (around 13ish) however I do get great highway milage (around 25) so I think maybe the city driving may be influenced by my foot. Both of my oxygen sensors are shot as I get a slow responce code for both of them. Right now I am just waiting til I go home for Thanksgiving to replace them. I am willing to bet that an excesively rich mixture probably ruined them.

As far as I know, my scanner does not display BLM's but it does display the short and long term fuel bank percentages. Those may be the same thing? Anways when driving around normally, I get a typical reading of about -14% on both sides, which equates to the computer commanding a lean mixture to correct a rich condition. Possibly my shot oxygen sensors would contribute to that. However it is my understanding that the oxygen sensors are not even used durring WOT so why would they be a factor in making a rich situation say if I do have an exhaust leak?

I am also not aware of my scanner having the capability to scan enhanced parameters, however the only thing that I would think could give some insight to knock retard would be the Ignition Timing Advance (Spark advance to add from base engine timing).

 

Previous statement:
I only mentioned poor fuel mileage because you said your gas mileage is pretty low..... hard to help you when you change your story.

Again, you said in the earlier quote you had new O2 sensors? Now you're saying you have bad O2 sensors. Which is it?

Yes

The PCM disables "learning" when you go WOT, but it still uses the long term fuel corrections it "learned" on closed loop. But only if it was adding fuel. Since yours are subtracting fuel, it will default to 0% correction. Since the PCM has to pull 14% fuel out in closed loop, its most likely running 14% too rich in PE mode (~WOT), since it does not use that 14% correction.

I'm not sure how to help, because of the discrepancies in what you are posting.

Spark advance displayed by a scanner is the lookup value from the timing table, minus any knock retard. Not sure how you translate the scanners value for timing advance to knock retard, without having the timing table in front of you along with instantaneous values of MAP and RPM used to look up the timing.

 

I aplologize for the changes in information, however this thread was started a couple of months ago when I did have new sensors which have since gone bad. I know I said I had bad mileage, however I never really did any strict highway tests. When I did do some highway tests, I did get around 25 mpg, even with the slow responce code always tripping. I possibly contribute my decent highway mileage to changing my thermostat back to the stock instead of the 160 before making the drive. Maybe it was making my car run too rich and thus crapping out my sensors?

Other than the poor performance, is there really any real possiblilty of damage from having so much fuel cut out from the mixture in my case, or is it all within a safe range? On my scanner, I happened to change my car from a '96 to a '95 to see if I could view any other PID's, and I noticed that even through WOT, it said my knock retard was 0 degrees. Is that even considered accurate since my scanner thinks my car is OBDI?

Anyhow, I sincerly apprecaite your help in this matter. I also sincerly apologize for my ignorance in some of the things I have said.

 

Go jump on a dyno with a wideband o2 sensor. A couple pulls will cost less than just throwing arbitrary parts at the problem. Also, if you're not running rich, coated headers have been rumored to kill O2 sensors until they heat cycle a few times and fully cure.

 

I'll never understand the, "Get a tune/false knock..." mentality with just headers.
I installed Hooker LT's w/ off-road pipe on my car when it had a LPE top end package including 1.6rr's and cut .4 off my ET and gained 4mph through the traps (had Edelbrock shorties w/ stock Y-pipe and cats prior to LT's). All this still using the stock LT1 KM.
I guess I'll never understand...

 

Your mph does seem low. My heavy vert like 3850 raceweight did 96 mph auto with 3.42 gears and minor mods like the magnaflow catback. The 2800 vig and asp balancer and 58tb wasn't on or were the 30 pound injectors.
I haven't installed my new fast afpr or racetronix pump and harness either. I think my car is running ok as buddies similar modded at the time ran 98 to 99 mph ,his was a
auto also with 3.23 gears and also minor mods, catback,CAI,no headers,no stall,no big power mods.
His car is about two to three hundred pounds lighter raceweight than mine.
I would expect 100 out of mine with headers. Also we are at 1900 feet above sealevel and that means my 96 is really closer to 99 at sea level and his 99 is more like 102.So 100 here on my car with headers would be 104 or so at sea level which is I think about right for an auto car trap with headers.
So I do think you have a problem. My cars traps vary widely sometimes due to I think knock retard or a fuel/ignition problem. I can get high knock one run and zero the next and my tuning and scantools seems inconsistent. I don't have wideband tuning just trying to tune with my maf translator and lt1 scanmaster or autotap.

I have gone thru my car in some areas. I have changed fuel filter and injectors. I have checked fuel pressure at idle and wot but it seems to be fine. I still bought an adjustable afpr more for tuning with the bigger injectors in the future and am hoping my new racetronix pump and harness takes care of any fuel issues. I want to replace my opti even though car has only 66000 miles on it and am getting no codes but more for preventative maintenance as installed CC305 and hopefully longtubes and LE2 heads next spring. I might go with dynaspark or delteq and new gm opti.
I plan on new plugs as also have zex wet kit to install and new wires.
I think I have some rocker noise when car is cold for sure and maybe a bit still there when warm. Have new 1.6 promags and all needed related stuff, studs,guideplates, pushrods so that should be fine when do the new cam and new lifters will go in there also.

I have installed the lt4 km but it dont' seem to help at all ,maybe I have a defective one,might try stock km or another lt4km and see if that helps. I am looking at taking out knock with toggle switch resistor mod or possibly get it reduced /eliminated with programming next spring.
So my car seems to run about right most of the time but some runs my mph goes down like yours to like 91 mph and its very frustrating. My ls1 on the other hand seems easy to tune and runs good with next to no knock.And is consistent as well.

Also quite a few people have problems with knock from exhaust rattles,it won't hurt to check under there and maybe take off the pretty much useless factory crossbrace thing.Some guys also seem to get knock from broken tranny mounts and of course loose headers and exhaust leaks too.

Another possibility for loss of mph and power is cloggin cats if you are running them. Clogged cats rob big power!!
But would think a clogged cat would be consistent in its power robbing. Also on ls1 cars they do run pig rich with headers and you do have to tune the mixture leaner to get your power. I have had headers on my ls1 and noticed this.Not sure if the lt1 acts the same. Guess find out next spring.

Hope this gives you some tips.I hate it when my car don't run consistent.

 

Well last night I was able to have someone watch my scanner while I did some WOT and normal driving around. When I went WOT, my knock retard went anywhere from 2 to 8 degrees retard. Normal driving around brought about 0-2 degrees retard. One thing that I noticed, whenever the TC is locked up and I lightly press on the gas, my knock usually went up to about 6 degrees. Now whether or not 2-8 degrees retard on WOT will cause a significant drop in HP or not, I don't know, but is it possible?

Another thing that is somewhat fishy about this all is when I previously said I had 0 degree retard, I was running 93 gas, however when I did the previous runs, I had 91 gas. Is it a possibility that since my car is running rich, and the computer is commanding a leaner mixture, that the leaner mixture would cause some real knock?

 

Ya like I said I've been getting knock retard even with my LT4 KM so I'm pretty sure it hasn't dont crap. I'm planning on a tune from Ion but I just don't have the money for it right now. I think rattles might also be a problem. Right now my y-pipe collector vibrates on my cat heat shield sometimes, but sometimes it doesn't. Usually durring WOT it doesn't vibrate, or at least I don't think it does. I have replaced my motor mounts with ES poly mounts but I think the vibration is coming from the gasket I'm using for the collector (It's one of those dead soft aluminum gaskets, works pretty well). I just need to grind it down a little bit and it should stop. I'm also running an ORP so I know a clogged cat isn't a problem.

 

I noticed that while on the freeway, my BLM's were right about at 110-112. Seems my car is running pretty rich so I'll for sure check again for exhaust leaks and I probably will replace my spark plugs and wires. The random missing and dieing at idle may possibly lead to a burnt wire...