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Thread: AFR bouncing up and down randomly

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Posts: 1-5 of 5
2012-07-15 18:54:59
#1
AFR bouncing up and down randomly
Lowport with S4s, Nistune, N60 MAF(regrounded), and 2.5 SSAC.
This is messing with my fuel mileage, and with my head. I'm really confused about this. I don't know if it's an injector issue, or possibly the oxy sensor, or the MAF, or something else like plugs/wires.
I've recently cleaned, and oiled my filter. Afterwards my AFRs went back up, and the next day down again. So, I cleaned the MAF, then the same thing. Today just driving to the gas station, and back it was up\down the whole trip back.
My plugs(BKR7E) are pretty fresh, and I checked them a couple weeks ago to find that they were normal. The wires are stock type made by standard ignition.
I put all new O-rings on my injectors about 6 months ago because one was leaking. My AFRs were good for a long time after. At cruise I'd normally see mid 15s to low 16s, but now lately I've been at mid 12s to 13s, and sometimes randomly in the high 14s.
Today I ordered the bosch 15727 oxy sensor after I read about regrounding if you have an SSAC. My mileage lately has been between 21-30 MPG, and it used to be 30+. I still drive the same as always with mixed city/highway.
2012-07-15 19:09:59
#2
Try a new battery. My car acted weird like that sometimes and we found my battery to be the issue.

Also go through and clean all grounds. I did this and it totally changed my tune after acting like your car. I went through and regrounded the maf, cleaned the ecu grounds, the main engine ground, and added a new ground from the chassis to the IM.
2012-07-15 22:33:15
#3
Originally Posted by nismo94tuner
Try a new battery. My car acted weird like that sometimes and we found my battery to be the issue.

Also go through and clean all grounds. I did this and it totally changed my tune after acting like your car. I went through and regrounded the maf, cleaned the ecu grounds, the main engine ground, and added a new ground from the chassis to the IM.


That's an interesting suggestion. Now that you mention it sometimes I have to play with my key to get the starter to turn over like my battery is going dead. I'll check that out, thanks.
2012-07-16 00:30:15
#4
I would have never thought of it. My car would start fine and all. My tuner was iffy when he noticed my AFR's leaned out when the headlights were turned off. He swapped the battery and the problem was a little better. I went through and did the grounds and the whole tune changed. Got a new street tune and it was solved.
2012-07-16 03:12:07
#5
You are the man! I have solid 15s at cruise on my AFRs now. I went through all of the grounds I could find under the hood and polished the terminals, and ground point with emery cloth. I greased everything as well. I made sure to sand down past the paint to bare metal. I did this to my battery ground too, since it's in the back now, and grounded to the spare tire area. She fires right up without stalling, or me having to play with the key. Also, to top this all off my damned radio picks up channels now, WTF? I never would've thought that a ground issue, lol.
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