Porsche 993 MAF & Durametric fault code scan

blondjohn · 01-29-2010, 06:44 PM

Wow! What a great Porsche community I just joined. God bless Dr. Ferry. I spent the past 2 hours reading archives here and Rennlist trying to find an answer to my question before I made a stupid post, all to no avail so here goes... 1995 993 was running great, parked it in my garage, won't start. turns over, sputters a little but won't run. Sputters tells me I've got spark, but maybe a fuel problem. Bought a Durameteric cable and software to to try and diagnose before calling a tow truck, Durametric tells me engine fault code "21 hot film MAF."

Questions: Is this code indicating a mass air flow sensor failure? Can a mass air flow sensor failure prevent engine from running at all from a cold start? I don't want to install a new MAF if this fault code is not the real problem. Will a Durametric code scan pick up a failed fuel pump on a 993? What else might be wrong?

Thanks for your help!

"Blond John"
San Diego Porsche owner since 1985
Current:
'95 993 6-spd coupe (Polar silver / blk)
'99 Boxster
Next:
997 Turbo?
Former:
1970 911T
1970 911E
1973 911 Street Racer built by Alan Johnson (Wow! Outside-stock sleeper left 1980's turbos in the dust to 170+ mph. A Porsche that burned rubber from 4th to 5th.)
1982 911SC (with full steel 930S slant nose body conversion done right)
1984 Carrera (Guards Red manual coupe, chipped and opened to breath)

rcwaldo · 01-29-2010, 09:23 PM

based upon your description of this problem, I would first try a new DME relay. This is pretty common and aligns with your symptoms.

RichieRoo · 01-30-2010, 03:54 AM

Hi John

I recently purchased the Durametric kit too. I agree it isn't immediately clear if
it's returning a fault code based on the sensor giving improbable values or the
sensor is genuinely indicating a fault (I'm going to disconnect the sensor and
retest to see if it reports an open circuit).

Try clearing the error codes, then try to restart. If the error code immediately
reappears it shows that this is a current issue rather than an intermittent one
from months ago.

I would guess (someone will correct me if I'm wrong I'm sure) that the car should
start even with a failed MAF. Think that the DME reverts to an emergency fuel map.

Hope it's sorted soon.

Rich

blondjohn · 01-30-2010, 12:17 PM

Chris and Rich,

Thanks so much for your very helpful responses. I cleared the "21 hot film MAF" fault code using the Durametric, and the code did not come back after trying several times to start the car. (I also believe the car should start with a failed MAF, but just run poorly, that's why I didn't believe the fault code was the real problem.)I ordered the 993.615.227.00 DME relay from Pelican Parts as suggested by Chris. $27 part is worth having in the glove box as a spare even if does not fix the current problem. The part should be here Tuesday. I'll post again then.

I think the Durametric is a good tool and worth the money for a Porsche DIY'er but it obviously won't elucidate every problem. Nice to have though to turn off the CEL from hell on the wife's boxster.

Thanks again! I really appreciate your help.

John

DW SD · 02-02-2010, 09:37 AM

Hi John,
I'm in North County SD and have a '95 engine in my early car. I've got an extra MAF in my parts box, if you need to try it?

I had some issues with my MAF while down at the PCA AX a few weeks back. I did not have the spare part with me. You can buy some MAF cleaner at NAPA. You can clean the film, but also a port at the base of the strut which holds the film. One of the techs that was there helped me with the cleaning process, from which I learned.

Doug

blondjohn · 02-03-2010, 07:36 PM

Chris Walrod,

You are a hero! I got the DME relay today, less than a minute to plug it in and start the car. Runs great again! Great tip. It would have taken me a lot longer, and possibly cost a lot more, to diagnose this problem without your advice.

Many thanks,

John

blondjohn · 02-03-2010, 07:44 PM

Doug,

Thanks for your generous offer of a MAF for testing use. Fortunately I don't need it right now. I'd love to see your early 911. Dropping a 993 engine in a '71 sounds like an awesome "inerpretation" of an RSR! Have you done anything with the suspension to improve the "tail in front of the nose" cornering tendency of the '70's 911's? I can't even count how many 360's I did in my 70's era 911's.

Cheers,

John

rcwaldo · 02-03-2010, 07:48 PM

Quote:

Originally Posted by blondjohn

Chris Walrod,

You are a hero! I got the DME relay today, less than a minute to plug it in and start the car. Runs great again! Great tip. It would have taken me a lot longer, and possibly cost a lot more, to diagnose this problem without your advice.

Many thanks,

John

Hey, no problem, it was nothing.

Very glad to hear its running again!

Have a spare in the glove box, this is quite common.

DW SD · 02-04-2010, 05:38 AM

Quote:

Originally Posted by blondjohn

Doug,

Thanks for your generous offer of a MAF for testing use. Fortunately I don't need it right now. I'd love to see your early 911. Dropping a 993 engine in a '71 sounds like an awesome "inerpretation" of an RSR! Have you done anything with the suspension to improve the "tail in front of the nose" cornering tendency of the '70's 911's? I can't even count how many 360's I did in my 70's era 911's.

Cheers,

John

John,
Yeah, my car is pretty modified, everything is gone through to lighten it up, strengthen the chassis and also decrease the spinning propensity. The LSD and wide rear tires help, but so do the adjustable sway bars, upgraded torsions and shocks, etc. I'll be down at the PCA autocross on 2/13, if you want to drop by (at Qualcomm)? Or you can shoot me an email and we can hook up some other time. I'm not doing many 360s - maybe I'm not pushing it hard enough!

I save the driving at the limit for the track-type events, though.

Hope to run into you sooner or later - glad your problem is resolved.

Doug