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Old 05-09-2021, 07:18 PM   #331
11 Second Club / Meet Coordinator
IROCZman15's Avatar
Join Date: Dec 2004
Location: Roxbury, NJ
Posts: 1,934
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Thank you all for the replies and ideas. Any help is much appreciated.

Larry: yes just one O2 sensor for the holly sniper. Unfortunately my DynoDon's headers only have a bung for the O2 sensor on the drivers side. It is in a good spot, but it is unlikely I will be drilling and welding a bung to the other side. I plan to remove these headers in the winter for a set of bigger long tubes, so I don't want to modify a good set of headers that will soon be for sale. I did not check plugs that night at the track, and as you mentioned, I did drive home after so the plug readings would be skewed.
-the fuel charge scavenging theory is something I have never even thought of. I see what you are saying. That would be WILD if that were happening. Wouldn't it be more pronounced at higher rpms such as at the top of 2nd or 3rd gear though instead of such a short period of time mid-rpm in 1st gear?
- The ECU Closed Loop Parameters can be adjusted by me. They can be left on al the time, off all the time, or pretty much anything in between. there are options for if I want it to deactivate at a certain Throttle position, rpm, etc. However, on my first 6 passes, I simply left Closed Loop (and Learn) on because I feel safer that it will make the right adjustments and save the engine if something went awry in the base tune. AS it turns out, this is exactly the opposite of what happened, and the closed loop feature went wild adding fuel, but if it needed to do it for some unknown reason, it did the right thing. I just then need to find out "what" caused it to add fuel.
- And yes, this has only ever happened in 1st gear and only at the track. Not during street driving, heavy street driving, burnouts, or anywhere else. Only 1st gear at the track. Once during my early April track day, once during the April 18th track day, and then 5 times (out of the 6 closed loop passes) from this weekend. Bizarre
-Ah man, every single time I drive past the shop, I look to see if there is any activity in the parking lot and if So I would instantly take a detour and say hi. But I don't want to be that annoying fella who just stops by randomly and barges in, so usually I just drive past. I can stop by next time!

Bishop: yes, the coolant temp sensor that I relocated is not jsut for data display on the handheld. The sniper uses it for lots of tables. However, prior to heading to the track I went out and bought one of the highly recommended accurate Standard TX3 coolant temp sensors. I wanted my tables and tunes to be just as I have had them for the past 14 months. So I installed the NEW temp sensor in the exact spot on the intake that the holley used to be in. I left the holley one in the passenger side cylinder head so that I did not have to drain coolant. I unplugged the connector from the one in the head and moved it to the new one in the intake. Basically, all temperatures were dead spot on all night at the track. I also don't pull away any ignition timing based on temperature until way higher temps from where it was running on Friday night. I do appreciate your thought process, but I thought of that all ahead of Friday and there should be no correlation between the CTS and this bog issue. Also, remember, this bog happened in early april and mid april when the CTS was untouched.

Matt: So, I am partially thinking it might be oxygen sensor related. I have read countless times about the Holley O2 sensors failing, but the symptoms people describe don't seem to match mine. Lots of topics on this at the Holley forum, and most I have read just have a sensor go pegged dead lean at 35 or something. I don't have that. After those two open loop passes I was confident in the base table and knew that the engine wasn't hurt or anything. Nor the trans. So, to test that idea that an O2 sensor was acting wacky, I loaded up a known good (non-drag race) tune and drove home, eyebaling the AFR readings the whole time. And, the whole time, the afr and o2 sensor did nothing that even suggested it was problematic. I drove 30 minutes, in all 4 gears on the way home, even with some moderate pulls on rt 80 just to run the engine and efi through its paces. Its fine, never bogged, never did any crazy afr readings.

feel free to keep the advice coming. Would love to get this issue resolved really soon, as I am due to bring the car for the roll bar install in a few weeks and would really like to have an 11.7x pass under my belt by then.
1987 IROC-Z - modified

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