Hello everyone, my troubles with my recently purchased 993tt continue. I thought I was in the clear after $2400 worth of service/repairs when it suddenly sprung a CEL light. I purchased a code reader and it read 1/1 codes - P1140, air fueling mixture. Does this mean my MAF needs to be replaced? Thanks for the help.
Enrique

 

P1140 is the code for "load calculation - signal implausible" and basic potential causes listed are "improper adjustment of operating cable for cruise control", "throttle position sensor" and "false air". What all was done during the service?

 

This is one of those codes that can be difficult to pin down. Unlikely the MAF. Have your mechanic do a "smoke test" to see if there are any vacuum or boost leaks. Also try clearing the code to seem how fast it comes back, and under what driving conditions. Where do you live?

 

My code reader's text was "air fueling mixture" for error code P1140. The tech did a smoke test and no leaks were found. This is the second time this same code pops up, about 600 miles apart. This second time around, I had recently topped off the fuel tank, cap was re-intalled tight. Other than that, I was just cruising on SR-91 w/b at about 80 MPH when the CEL came on. I've cleared the code but need to smog the car for registration. I haven't been able to do that due to a lack of readiness on some of the monitors. ARGH!
I live in Murrieta, Ca.
Thanks for the feedback fellas.
Enrique

 

My mechanic was able to read my readiness codes with his more sophisticated OBD2 reader. When they all looked good, I quickly went to the Smog station and passed with flying colors. I occasionally get an 1140 code, and after a while, it resets itself. My code seems to happen when i'm cruising or coasting with very light throttle. There must be something right on the edge, but we haven't found the root cause yet. Please keep in touch... perhaps we have the same root cause.

 

I had this code come on and it took forever to diagnose. I had Joel Reiser in Rochester do a vacuum leak test and it wound up just being a loose hose and an easy fix. Hope yours is as simple, but before you waste any more $ find someone who can do that test for you. Do a search for that code # and you'll find my string of frustration.

 

ca993twin,
How long before your readiness monitors reset? Was it a specific driving sequence or just miles? Thanks.
Enrique

 

I just drove the car for my typical 100 or 200 miles and then had my mechanic check them. I didn't try to follow the proscribed sequence. BTW, not ALL of the readiness codes need to be set for the smog test... I think you can have one or two still reset, and they can still test the car. If you have trouble with the readiness codes, you can take your car to a referee station... they are well acquainted with the Porsche-peculiar problems, and can run a smog test even with all of the readiness codes reset... I think. Worth a phone call to your local referee station to scheck on this. Don't mention the CEL! You cannot smog a car with a CEL.

 

ca993tw,
I will try a smog referee. You're a wealth of porsche information. Thanks again.
Enrique

 

Enrique,

Thanks, but be careful... I just make most of this stuff up.

I would get the CEL cleared, then go to a smog station. They will not be able to pass you because the readiness codes aren not set (maybe). Tell the referee station you had to disconnect the battery for something or another, and that is why the readiness codes are reset... do NOT mention the CEL.

I finally got a cheapo OBD 2 reader ($39.95 at Harbor Freight) so now I can read the codes and clear the CEL.

 

I have a code reader, and cleared the CEL myself. Smog station said I needed to drive the car until the monitors turned on. I'll drive it a couple hundred miles and plug in my reader, it shows whether or not the monitors are ready.

 

Like others have mentioned, vacuum/boost leak is the most common cause of this code. If the code just popped up after major work was done to the car, this seems even more likely since the IC/hoses have to be off to do anything on these cars. Double check that the turbo compressor outlet-to-IC hoses are on all the way and tight, on both the IC end AND where they attach to the turbo cold side outlet. If you don't tighten the clamps just right, they can leak boost. Also when smoke testing these cars, you have to look real close since IC has to be in place of course and it blocks everything (take the shroud off, though).

Of course, the MAF could be the cause as well, they can go bad, but an experienced tech would have to look at airflow the numbers w/ a scan tool in order to tell . . . . do you by any chance have a K&N filter that has been recently reoiled? If so toss it and get a factory paper filter---the oil can coat the hot wire of the MAF sensor and skew the readings.

Anyway, like others said, first clear the code and see if it comes back; if it does you'll know it's a problem.

---Chris A.

 

I bought an OBD reader and for a laptop and could clear the code - it kept coming back and after much trouble shooting it was a loose hose hose clamp. The car felt good and as if it were making good power, but once the hose was tightened, no more CEL!

 

Thanks for all the feedback fellas. After only sixty miles the same code popped up again. I'll double check all hoses and clamps that I can get to. Maybe something came loose after it was smoke tested. Or maybe my MAF is busted..... How do you test for just the MAF sensor? Buy one, replace it, and see if the CEL returns? Thanks again.
Enrique

 

Like I said in my previous post, you need to have someone who knows what to look for monitor the airflow numbers at idle and under varying load conditions. Also look at the fuel trim numbers. Those usually can help pinpoint a bad MAF sensor . . . However a bad MAF sensor is usually associated w/ poor running/hesitation, which you did not mention in this post, but you had mentioned such a problem in a previous thread. Was that ever resolved?

Other things to check are cruise control cable as previously mentioned and your TPS sensor, though a bad TPS will usually manifest itself as a slight hesitation or stumble where the wiper arm has worn the track in one spot. . .

Have everything checked out before throwing a MAF sensor at it.

(BTW I typed this post on my new iPhone just for fun---it took awhile but this thing is seriously cool! The 4 yr old dinosaur Nokia had to go!)

---Chris A.