dragunbayne

I'm pretty sure I don't, but we'll put some air to the tailpipe and check it out. It is running near 18 when cruising closed loop around 68mph. If it is accurate I honestly don't mind what it runs at idle and around town and 45mph cruising. One problem may be the header. The front O2 only reads off one cylinder. At some point I would really like to get a different header, or go turbo!

jakermeister

iTrader: (11)

I've heard of people using a smoke machine to see where its leaking. I've just used soapy water when the exhaust is cold on startup.

dragunbayne

I think my fuel pump may have an issue. After doing a WOT run it was extremely lean, so much so that when I got off the ramp and stopped it stalled. It took awhile to richen back up a little. When it did it shot to 14.2, bottomed out and slowly went to where it typically is in closed loop.

EDIT: Just to be sure I got up on the interstate in a more tame fashion and it did not go super lean while cruising.

dragunbayne

Some more testing. Our mornings are cool right now and that's when it stayed normal. The afternoon is fairly hot however and it was extremely lean when I drove it and let it idle. The coolant temps and airflow temps were consistent both times however.

dragunbayne

What should my load be at idle? I was just reading and someone having similar issue to me it was suggested that their load was too low so their MAFcalcs or MAPcalcs was probably too low. I think I'll try upping my MAF scaling. I've made some fairly large adjustments to the smoothing, but this only affects fueling and does not correct the airflow reading if it is incorrect right?

EDIT: Scratch that. Adjusted by 10 each way and it made no difference. I'm going to replace my front O2. It just keeps occuring to me that closed loop is centrally controlled by it and that if my trims are nearly zeroed but it's lean, then the O2 is out of whack.

jakermeister

iTrader: (11)

I don't know the load off the top of my head. I still think you may have a exhaust leak. Try the soapy water on the manifold and downpipe before messing with your settings. If evoscan says you're with -/+5 of your stft then I would go with what it says and check for leaks. Closed is controlled by the o2 sensor and will try to keep you around 14.7 afr. Are you running a aftermarket manifold? If so post a pic.

dragunbayne

Yes my low trim is -.4 and mid is -3. I will definitely check for leaks. I have one of the stainless steel 4-2-1 headers from eBay. I'd like to get something better eventually, but not RRM it's too expensive. I got what I have because my exhaust was basically shot and I was strapped.

jakermeister

iTrader: (11)

I'm just interested in where the o2 sensor is placed. If its too close to the head it can get burned out quick. Some manifolds have the sensor a few inches away from the head and I think its too close. I would just go with what your trims say and leave it as is.

dragunbayne

It is quite close, I can get a picture later. I did get it replaced under warranty. It has only made maybe a minor difference. It was pretty white. I've gotten my low trim to 0 and mid to -1.5. It's not always super lean, just under certain circumstances, I can tell by how it runs. I swapped the screen and restrictor plate to my original MAF since I know it's condition. That seems to have made a positive difference also. It is no longer almost leaning itself to death when I stop, so you may have been onto something with the bad MAF theory. I will also be checking for exhaust leaks after work and checking my vacuum just to be sure. I will hopefully be able to start on my timing soon, my WOT fueling is almost where it should be.

jakermeister

iTrader: (11)

Yeah the screen will definitely throw your readings off if you have it off the MAF. If you have a SRI and you did not recirculate the hose from the valve cover back into the intake tube that can throw your readings off a little. For the vacuum sources I've read some brake cleaner(?) can help. Its suppose to be throw the idle off a bit when it sucks in the cleaner.

dragunbayne

My original MAF had the screen but the screen on the junkyard one was in better shape. Since switching the MAF my trims are calling for more fuel which I believe to be a good sign. I did hook up the hose from the valve cover, car doesn't run well at all without it. Most of my vacuum lines are new except the ones that have a valve or restrictor in them. I just figure it never hurts to hook up the vacuum gauge and run some tests, you can learn a lot pretty quick that way. On a side note, I almost took the screen out once, but saw the warnings on here first. It was a common mod on GMs and worked fine with them. I really appreciate the guidance Jake.

dragunbayne

Haven't gotten to test for the exhaust leaks, but the vacuum test indicates a possible issue that I think would explain the lean readings after WOT. I'm pretty sure my valve springs are weak. From what I understand this can cause the hydraulic lifters to compress and cause the valves to not completely close for awhile while they bleed themselves back out causing the lean condition and roughness on the highway. I'm guessing the rebuilt head i bought didn't have the springs replaced.

dragunbayne

Hey! I'm back to working on my tune. I have a couple of questions based on some current reading and observations. Is there a base timing that is added to the number in the timing table? I don't believe there is, but I wanted to ask. Second, how can I log vacuum in Evoscan?

marcouxa1

There's no way to log vacuum but you can log load.....at idle with +-20 vacuum you should be around 22-25 load if i take my car for an example. As for your base ignition timing there's no such thing besides the EGR and cold start timing maps. If your ignition map is 16 deg of timing at 1250 rpm and the number is not accurate in your log maybe your maf is not adjusted properly?

dragunbayne

My idle load is a little lower than that. I didn't think there was a base ignition map, but wanted to be sure. As far as the other ignition maps, those aren't mapped for my ROM unfortunately. I really appreciate the info.