Well I went to the local auto parts store and picked up some assorted vacuum tube caps. I checked out the VFAD port on the throttle body and not having checked it before, it was actually not capped so I capped it. I have started it three times now with no check engine light. I will keep starting it and see if it resurfaces. I'm pretty pumped that this might be the solution. I have attached some readouts of the LTFT and STFT while driving. Thanks everyone for the feedback.

It is still bouncing around a bit during idle, but while driving it balances out. I'll keep you posted.

Thanks,
RotaryLife99

 

Hey guys,

I definitely think that the problem is solved. I have started it about 7 times now and no code. It's also idling smoother and running not noticeably different, but strong. This has probably been an issue since day one of my ownership, but I had no clue.

Thank you all for you input,
RotaryLife99

 

Nice! STFT will bounce within a certain range, that's normal. LTFT looks like it's coming back to normal.

 

Thank you so much guys, I really appreciate it.

 

Good stuff , always good to see someone not only fix the problem but come back to us with what the problem was !

 

Yup that was definitely it, vacuum leak. Good to hear you pinned the problem down

 

Hello All,

I have just reached 114.5K miles and she is still kicking. I am slightly concerned with one thing which may or may not be a big deal, just not sure. This has to do with my fuel trims yet again. I just replaced my dryflow filter on my AEM CAI because I screwed up the old one with the wrong cleaner. I also installed a relatively cheap catback exhaust from Manzo. Not sure if either of those are the cause of this current issue, but here it is. When I am on throttle it reads 6.2 on my LT fuel trim and roughly 0 on ST Fuel trim. The concerning part is when I'm in neutral or idling. The LT reads 15.6 and the ST is 0.

I have attempted a couple of different things to fix this from reading in the forum, but to no avail. I had the vacuum system smoke tested for a vacuum leak, nothing. I changed the wires, plugs, and coils. Does anyone have any idea what might be causing this linear pattern in my fuel trims or is this completely normal?

Thanks!

 

When you have that high LTFT at idle, what's the airflow g/sec and rpm?

​​​​​​Have you cleaned the MAF while you were messing with different filter oils?

 

The pattern is normal. The ECU has different LTFTs for MAF rates below 8 g/s, 8-20 g/s, and 20+ g/s. If you plot LTFT and MAF rate on the same graph, you'll see what I'm talking about.

That said, +15% LTFT is indicative of a problem. It's not a huge problem since the ECU is compensating for it but still an issue. It could be a vacuum leak somewhere, a dirty MAF or turbulent airflow at the MAF.

There's no way an exhaust would cause a change in your fuel trims. The air filter might if you goofed with the filter and got solvent or oil on the MAF. If you haven't cleaned the MAF with proper MAF cleaner, do that. Check any airflow modifying features (screens, straighteners, etc) between the filter and the MAF. It could also be a bad front O2 sensor but I'd bark up that tree last.

 

The filter that I have on my AEM CAI is a Dryflow filter which doesn't use oil on it, at least that's what it says, so I never oiled the replacement filter. I had a run in with very cheap coils that I decided was a good idea to purchase. I attempted to do a seafoam treatment and "flooded it". When I realized it was the cheap coils I bought a set of coils that are OEM spec/ better and installed those. It started right up. Is it possible that during this time period I may have messed up my MAF or front O2 sensor? I have cleaned my MAF sensor since this has happened and changed the engine oil as well. Any particular way to know if this is possibly due to a bad front O2 or a MAF sensor without buying new ones and installing?

A side note, I have a catless BRH midpipe as well ( No codes thrown from this)

Loki - I'll try to grab the airflow rate/rpm when it's at idle when I get a chance. ( It usually idles around 800, but recently since this problem has occurred it has bobbed around a slight bit like a rougher idle ( up to 850 or 875 and down to 775 to 750) )

On a side side note - the tech that smoked my vacuum system said he was unable to communicate with my fuel trims with his computer. Could that be the symptoms of a bad MAF or just a shotty connection on the OBD II port?


Thanks

 

Probably a crappy technician.

 

You're probably right.

 

These are the conditions at idle. Let me know if anything looks off from this.

 

I am not sure if these tell anything about the O2 sensors, but it was worth a shot. Let me know if anything looks off from these. These are conditions at idle as well.

 

I also cleared the computer/ did the 20 brake pumps to clear the computer trick and will see if sitting and idling to working temp does anything.

 

I'm new to this so I don't know how this works so don't yell at me, but anyways i have a 2005 Shinka and its running kinda rough as like when idle it shakes but when i rev it above 1k RPM it stops I don't know if that's normal or whatever but anyways i'm having a problem when my car idles for a little while smoke starts to come out where the coolant reservoir is located and I don't know what the problem is I was thinking It could be the water pump went bad or the thermostat went bad! thank you for any help givin!