Running too lean p0171
 

Hey guys so I recently got a p0171 about a couple weeks ago and I've been trying to figure it what it could be... I've checked my vacuum lines, pulled apart my aem cai and checked the screens and they were perfectly lined up.

I'm running a custom stage 1 cobb map at the moment, but I was previously running a custom stock style map when the CEL started. By custom I the have radiator fan turn on temp coming on at 190, OMP values multiplied by 1.25, idle upped to 875...

It's pretty late right now, so I figured I would post a data log and I'll update this thread later in the morning. If someone wouldn't mind checking it, and see if they notice anything strange. When looking at my AFR it honestly looks about the same as it previously was before I got the CEL... My car is performing the same, and still feels strong. I'm not getting any power loss at all. My idle has gotten slightly rougher than it was though.

Some more info

Cleaned my MAF sensor, ESS sensor looks pretty clean last I looked at it about a week ago. Just topped off my oil a couple days ago, I'm running a FD approved oil for premix at half an ounce per gallon... I've reset my CEL with my cobb, and have since reset my fuel trims when I changed maps.

OEM style coils at about 7k miles
Spark plugs at about 10k miles
Mazda reman with 7k miles

Anyone?

I also forgot to mention that I checked the nipple behind the throttle body, seemed fine and was connected...

Posted From RX8Club.com Android App

You sure the map is OK?...you have an idle FT problem mostly..it drops off idle to a value that won't cause the CEL..Did you check all the vac lines for leaks?

I would go back to a stock map and then see what happens from there..otherwise you have no place to start

The custom map is certainly suspect if you touched ANYTHING related to the MAF and/or fuel tables. Since it sounds like you have access to ATR I would first compare your current MAF, fuel and correction tables to the base map ones.

Also if you did not preserve the COBB base map then you likely need to uninstall and re-install it to get it back.

Also, where are you fuel trims now? Since you reset them you may have uncovered a long latent problem.

I'm 100% sure the maps are okay.

Like I said the only values I changed were the ones listed. I haven't messed with any fuel trim values, MAF, ignition...

The problem first started in my custom stock map I reset the code twice and it came back after 50 miles or so, I then cleaned my MAF, pulled apart the AEM to check the screens and changed to the stage 1 map, also checked for loose vacuum cables. The CEL came on last night after several drive cycles and maybe about 200-300 miles of driving. I thought cleaning my MAF fixed the issue...

I've been running the custom map for several months now, about 6 months without any problems... I did have a misfire issue now that I think about it. I pulled my plugs reinstalled them, cleaned the MAF and this happened during a weird weather shift. After all that and resetting my fuel trims the misfire went away and everything was normal. Would a premature failing ignition coil or plug cause this problem?

Posted From RX8Club.com Android App

failing ignition woud likely cause you to run a little richer, not leaner.

uninstall the map.

Can you explain the idle FT problem? My fuel trims were reset many drive cycles ago about 300 miles or so of driving.

Posted From RX8Club.com Android App

Okay of course yeah that makes sense... Would be richer.

I can uninstall the map, but like I said it happened using the custom stock map. So I'm pretty sure the problem will come back.

I forgot to mention I also ran a quarter tank of gas with sea foam incase this was a clogged fuel injector problem. I ran a very minimal ratio at only a ounce per gallon. I might run some more.

I guess my best bet would a intake leak problem? While I have checked, I wouldn't say I've been very through...

Posted From RX8Club.com Android App

If you go 100% stock map wise and the problem still occurs all that's left is your AEM... but it's really rare to hear of problems with the AEM unless you already had MAF or vacuum problems.

I'm not saying 100% your map is hosed... just trying to keep you on a path of scientific experimentation to ultimately reach root cause :)

So I was driving home from work... I decided I was going to thoroughly check the car for a vacuum leak. And I was driving home I realized the CEL turned off... :dunno:

I didn't reset my code, didn't reset my fuel trims, didn't change maps... The CEL was on for the past two days and it's pretty strange that it just turned off like that.

Hey guys I want to conclude this thread... So like I said the CEL turned off by itself yesterday.

Today I was poking around my engine bay feeling all my vacuum lines, and I found a loose plug that goes under the throttle body. I was able to easily push it in and snap in place. I pretty sure that was my vacuum leak...