Jumpy AFR at idle

borat · Post by **borat** » Sat Oct 25, 2008 9:42 pm

Recently my AFR has been jumping from the usual 14-15 range to the 17-18 range every few seconds, and sometimes dipping to 12-13. I haven't touched the .cal in almost 9 months. I haven't adjusted my valves since... ever. I figure it's about time, since I'm at 75k miles now. Any other ideas as to what's going on? Edit: setup 99 prelude base 5spd JRSC ~7 psi

jacer63 · Post by **jacer63** » Sat Nov 01, 2008 7:50 pm

weather change maybe? mine seemed to that when the temps started going down.

xenocron · Post by **xenocron** » Sat Nov 01, 2008 8:10 pm

75k miles in 9 months? Whoa....

sohcd16y8 · Post by **sohcd16y8** » Sun Nov 02, 2008 2:21 am

I think he means 75k in the life of the car.

Orthello · Post by **Orthello** » Sun Nov 02, 2008 11:01 am

jacer63 wrote:weather change maybe? mine seemed to that when the temps started going down.

That's what I exerience too. Temps are going down.. AFR is going up (running full open loop)

Post by **Gaskleppie** » Sun Nov 02, 2008 11:22 am

My AF is not going up even when it is colder. I am running the IAT sensor in the intake tubes, not the regular sensor in the manifold. maybe thats the difference. I run the stock IAT compensation tables... question, are you running open or closed loop?

borat · Post by **borat** » Sun Nov 02, 2008 4:12 pm

I was running closed loop, so I disabled it to check. Still does the same thing. I should just adjust the valves to see what happens since it needs it anyway, it's gotten pretty noisy. Not that I can hear anything over the nose of the charger rattling like crazy, that also needs a rebuild.

Post by **Gaskleppie** » Sun Nov 02, 2008 5:29 pm

Just make a datalog and observe all measurments and corrections. Maybe the ECT is higher than normal, maybe the bat voltage is jumping, things like that.

Orthello · Post by **Orthello** » Sun Nov 02, 2008 5:41 pm

Gaskleppie wrote:My AF is not going up even when it is colder. I am running the IAT sensor in the intake tubes, not the regular sensor in the manifold. maybe thats the difference. I run the stock IAT compensation tables... question, are you running open or closed loop?

hmm... intresting.

butch11a · Post by **butch11a** » Mon Nov 03, 2008 12:55 am

could be the battery voltage, mine changes a/f when the fan starts, i'm using larger fans which seems to draw a large current suddenly, then the a/f levels off....

CRX2 · Post by **CRX2** » Mon Nov 03, 2008 1:54 pm

When all correction table are correct, the AFR should not change much... IAT. Look while datalogging at your ECT and BATT correction tables? When the AF changes it could be caused by one of these tables...