Glendoramike:

I noticed that part of your post disappeared and it stumped me for a while until I figured you'd pulled it

I've been through everything you mentioned (except the flashlight bit on my - new - air filter; that's a new one for me) as I systematically sort my way through the JTIS.

I actually had a new (rebuilt) MAFS in hand at the very start and took a bunch of readings with it vs. the old one. Some people report their MAFS being "stuck" and giving only one or two readings or no readings at all. Not my case, in fact the old one tracked pretty well to standard and to the new one also. So I moved on.

After not finding anything else obviously wrong I'm circling back to - as you point out - the simple stuff, the MAFS. I should have run it for a day or so with the new MAFS. Live and learn.

 

Is it fixed? The ECM needs a good idle and a good drive to re-learn or learn about changes. Especially parts changes.

 

Don't know yet - the part hasn't arrived. I'll know Monday.

You raise a good point - I wonder how long it takes to relearn. MY LTFT values are pretty dynamic, changing every few seconds (Though not in any readily recognizable relationship to engine speed). Seems like it would only take a minute or two.

Interestingly, yesterday my test driver (GF) noted that after passing through a new, brief, period of Restricted Performance for a few miles that message and the ever-present CEL cleared itself on her last trip.

I don't think the JTIS specifically mentions whether any particular code is self-clearing or not. You might be able to infer whether it is or not from the setting conditions...

When I get back to the car I'm going to look at Pending Codes and see what coming up!

 

the lean/rich CEL does clear itself when the limited condition (the one that triggered it in the first place) is repeatably absent for a certain number of drive cycles...three I think.

 

here's the data I promised...

Ignition turned to ON, w/o a start


At idle, in PARK


At 2500 RPM, in Park

 

Well, just before I installed the new (rebuilt) MAFS the codes cleared and the RP went off -pending codes were P0172 and P0175 so I figured it was just a matter of time so I installed the MAFS.

I watched the LTFT and STFT live while driving and the LTFT were still negative 100% of the time but not particualrly high, <-10. MAFS looked normal.

On a warm restart the engine idled rough then raced and I could hear a fast "clicking" which I take to be the VVT injectors loading the cams. The MAFS reading was 399.47!
After a couple of restarts the MAFS reading went to 4.5 or so and everything was normal.

I noticed that this MAFS ALWAYS Starts at 399.47, then drops to a normal idle reading a fraction of a second later. Apparently, it missed the trigger to drop down and told the ECU the engine was WOT. No codes. This has happened once before about a year ago - I chalked it up to a temporary poor Throttle body connection but never really felt good about that diagnosis...

For the rest of the 50 mile trip it acted normal. After another warm restart the LTFT readings all of a sudden popped into Positive range but at values below 10.

My test driver is out with it today so we'll see what transpires.

 

You could force a 'new' startup trim level by doing a hard reset.

Mine had the same behavior, restart rough (but on only on a cold start, now thats totally opposite), then raced. If the MAFs on both of ours is new/rebuilt, and it still does it, perhaps its not the MAFs, but something else screwing with the sensor output, throwing out that crazy air rate.

After 3 weeks now w/o any trouble, over the last couple days, I have started experiencing a slight racing ... again. Dang. The weather is back down into the low 50s, perhaps that has something to do with it.

 

I'll do a hard reset that tonight. Before, though, I'll put the scanner on with the old MAFS and see if that one does it too...and report back.

My test driver reported in at lunch and she said it's running fine today.

 

whats the status on the xk? just curious

think I fixed my 'racing' on a cold start, and elevated lean fuel trims. My PCV line returning from the manifold right side to the throttle body elbow (under it). Line was either cracked, and or the o-rings were no longer sealing the norma connectors well enough. Sucking alot of air into the engine.

 

I was driving it a bit before I closed out this thread...

The new MAFS seems to have cleared up the Rich running condition. I learned a LOT along the way so the process was worth it to me. For everyone else, just replace the MAFS right off and be done with it!

Yes, leaking lines from dried connections, split plenums and hose ends that allow unmetered air into the system will set Lean codes. Thats why lean Codes are much more common than Rich codes. I'm glad yours worked out easily.

 

DId you have any gas smell with this? I'm getting the same codes intermittently, the tail pipes are BLACK, and I sometimes smell fuel.
I've cleaned the MAF, but haven't replaced it or done any readings on it (new territory for me). It's getting worse (running rich more often, both banks) so I'd like to fix it. New MAF?